Investigating the Provenance of Iron Artifacts of the Royal Iron Factory of São João de Ipanema by Hierarchical Cluster Analysis of EDS Microanalyses of Slag Inclusions

Mamani-Calcina, Elmer Antonio; Landgraf, Fernando José Gomes; Azevedo, Cesar Roberto de Farias

doi:10.1590/1980-5373-MR-2016-0444

Abstract

Microstructural characterization techniques, including EDX (Energy Dispersive X-ray Analysis) microanalyses, were used to investigate the slag inclusions in the microstructure of ferrous artifacts of the Royal Iron Factory of São João de Ipanema (first steel plant of Brazil, XIX century), the D. Pedro II Bridge (located in Bahia, assembled in XIX century and produced in Scotland) and the archaeological sites of São Miguel de Missões (Rio Grande do Sul, Brazil, production site of iron artifacts, the XVIII century) and Afonso Sardinha (São Paulo, Brazil production site of iron artifacts, XVI century). The microanalyses results of the main microconstituents of the microstructure of the slag inclusions were investigated by hierarchical cluster analysis and the dendrogram with the microanalyses results of the wüstite phase (using as critical variables the contents of MnO, MgO, Al₂O₃, V₂O₅ and TiO₂) allowed the identification of four clusters, which successfully represented the samples of the four investigated sites (Ipanema, Sardinha, Missões and Bahia). Finally, the comparatively low volumetric fraction of slag inclusions in the samples of Ipanema (~1%) suggested the existence of technological expertise at the ironmaking processing in the Royal Iron Factory of São João de Ipanema.

Keywords:
Archaeometallurgy; Royal Iron Factory of São João de Ipanema; Microstructural characterization; Slag inclusions; Hierarchical cluster analysis

1. Introduction

This paper is a product of a research project focused on the Brazilian ironmaking history in the XIX century, from the point of view of the microstructural analysis of the slag inclusions found in iron objects. One of the objectives is to explore whether the Royal Iron Factory of São João de Ipanema was a place where an up-to-date engineering was effectively at work. The other objective is to develop a new methodology using the EDS microanalysis of the slag inclusions in order to group and separate the samples in accordance with their sources: the Royal Iron Factory of São João de Ipanema; the Archaeological site of Afonso Sardinha (State of São Paulo, Brazil), Archaeological site of São Miguel de Missões (State of Rio Grande do Sul, Brazil), and the Dom Pedro II Bridge (State of Bahia, Brazil, using iron imported from Scotland).

The Royal Iron Factory of São João de Ipanema was founded in 1810 in the city of Iperó (State of São Paulo, Brazil) and its blast furnaces began the production of pig iron in 1818, being the only two blast furnaces in Brazil in operation up to 1888¹1 Baer W. The development of the Brazilian steel industry. Nashville: Vanderbilt University Press; 1969. 202 p.^-²2 Santos NP. A fábrica de ferro São João de Ipanema: economia e política nas últimas décadas do segundo reinado (1860-1889). [Master's Dissertation]. São Paulo: Faculdade de Filosofia, Letras e Ciência Humanas, Universidade de São Paulo; 2009. 180 p.. This factory produced thousands of tons of iron bars in its lifespan, initially with the process of direct process and, subsequently, exclusively with the indirect process (pig iron production in the blast furnace followed by refining) until 1926³3 Landgraf FJG, Araújo PEM, Schroeder R. Ipanema e os alemães. In: Martius-Staden-Jahrbuch, 61. São Leopoldo: Oikos; São Paulo: Instituto Martius-Staden; 2016. In Press.. In a nearby site and using the same source of iron ore, a Portuguese explorer, Afonso Sardinha, had produced a few tons of iron in the late sixteenth century by direct process. This production spot, referred as Afonso Sardinha site, is considered to be the first exploration of the mine of magnetitic iron ore located in the Araçoiaba hill⁴4 Zequini A. Arqueologia de uma fábrica de ferro: Morro de Araçoiaba, séculos XVI-XVIII. [PhD Thesis]. São Paulo: Museu de Arqueologia e Etnologia, Universidade de São Paulo; 2006. 223 p.. Some ferrous artifacts from this site were collected by an archaeologist from Museu Paulista, Dr. M. Andreatta, in 1983⁴4 Zequini A. Arqueologia de uma fábrica de ferro: Morro de Araçoiaba, séculos XVI-XVIII. [PhD Thesis]. São Paulo: Museu de Arqueologia e Etnologia, Universidade de São Paulo; 2006. 223 p.. Additionally, iron objects were collected at several archaelogical sites of the Missões region, in Brazil, which were active in the XVIII century. It is still not certain whether these ferrous artifacts were produced⁵5 Zanettini PE, Camargo PFB. Arqueologia no Parque Fonte Missioneira: Programa de prospecções arqueológicas Parque Fonte Missioneira. São Miguel das Missões, Rio Grande do Sul. Relatório Final. São Paulo: Zanettini Arqueologia, Instituto de Patrimônio Histórico de Artístico; 2010. 142 p. from local iron ore or imported from Europe⁵5 Zanettini PE, Camargo PFB. Arqueologia no Parque Fonte Missioneira: Programa de prospecções arqueológicas Parque Fonte Missioneira. São Miguel das Missões, Rio Grande do Sul. Relatório Final. São Paulo: Zanettini Arqueologia, Instituto de Patrimônio Histórico de Artístico; 2010. 142 p.. During XIX century, important structural components were usually imported from Europe, such as the iron parts of the Dom Pedro II Bridge, in the State of Bahia, which was built between 1882 and 1885 with elements brought from the United Kingdom⁶6 Marques AC, Borges AR, Bittencourt TN. Evaluation and modelling of wrought iron bridge in Bahia. In: Chen A, Frangopol DM, Ruan X, eds. Bridge Maintenance, Safety, Management and Life Extension. Boca Raton: CRC Press; 2014. p. 334-339..

Ferrous products manufactured before the twentieth century contain much large amounts of slag inclusions in their microstructure, typically higher than 3% in volumetric fraction. These inclusions contain various oxides, which are related in terms of chemical composition to the whole production system. In this sense, the chemical composition of these slag inclusions is defined by the composition of the different materials and raw materials used during the manufacturing process, such as iron ore, charcoal ash, furnace lining, fuel, hearth lining, fluxes and etc. The investigation of the chemical composition of slag inclusions in ancient ferrous artifacts has been used to determine some technological and historical characteristics of the metallurgical processing, including their possible provenance⁷7 Dillmann P, L'Héritier M. Slag inclusion analyses for studying ferrous alloys employed in French medieval buildings: supply of materials and diffusion of smelting processes. Journal of Archaeological Science. 2007;34(11):1810-1823.

8 Blakelock E, Martinón-Torres M, Veldhuijzen VH, Young T. Slag inclusions in iron objects and the quest for provenance: an experiment and a case study. Journal of Archaeological Science. 2009;36(8):1745-1757.

9 Crew P. The experimental production of Prehistoric bar iron. Historical Metallurgy. 1991;25:21-36.

10 Desaulty AM, Dillmann P, L'Heritier M, Mariet C, Gratuze B, Joron JL, et al. Does it come from the Pays de Bray? Examination of an origin hypothesis for the ferrous reinforcements used in French medieval churches using major and trace element analyses. Journal of Archaeological Science. 2009;36(10):2445-2462.

11 Charlton MF, Blakelock E, Martinón-Torres M, Young T. Investigating the production provenance of iron artifacts with multivariate methods. Journal of Archaeological Science. 2012;39(7):2280-2293.

12 Buchwald VF, Wivel H. Slag Analysis as a Method for the Characterization and Provenancing of Ancient Iron Objects. Materials Characterization. 1998;40(2):73-96.

13 Disser A, Dillmann P, Bourgain C, L'Héritier M, Vega E, Bauvais S, et al. Iron reinforcements in Beauvais and Metz Cathedrals: from bloomery or finery? The use of logistic regression for differentiating smelting processes. Journal of Archaeological Science. 2014;42:315-333.

14 Maia RR, Dias SM, Azevedo CRF, Landgraf FJG. Archaeometry of ferrous artefacts from Luso-Brazilian archaeological sites near Ipanema River, Brazil. REM, Revista Escola de Minas. 2015;68(2):187-193.

15 Maia RR. Análise de inclusões de escória em amostras arqueológicas da fábrica de ferro de Ipanema. [MEng. Dissertation]. São Paulo: Escola Politécnica, Universidade de São Paulo; 2014. 209 p.^-¹⁶16 Maia RR, Azevedo CRF, Landgraf FJG. Análise de inclusões de escória em amostras da fábrica de ferro de Ipanema. In: 67º Congresso ABM Internacional; 2012 Jul 31 - Ago 3; Rio de Janeiro, RJ, Brazil..

In 2007 Dillmann and L'Héritier⁷7 Dillmann P, L'Héritier M. Slag inclusion analyses for studying ferrous alloys employed in French medieval buildings: supply of materials and diffusion of smelting processes. Journal of Archaeological Science. 2007;34(11):1810-1823. presented a methodology applying data processing on the EDX microanalyses of slag inclusion of 170 ferrous objects sampled from several archaeological sites and monuments. They built bivariate graphs showing the contents of some oxides present in these inclusions (for instance, % SiO₂ versus %Al₂O₃; %CaO versus %K₂O; and %MgO versus %Al₂O₃) and applied data filtering and linear regression (assuming the line passing through the origin) techniques to investigate the provenance of these objects. They determined the "signature" of each production site by using the values of the slope of the linear correlations of the various bivariate graphs. Additionally, they proposed another bivariate map featuring the oxide contents of the slag inclusions (% P₂O₅ versus [%Al₂O₃+%MgO+% K₂O]/%FeO ratio) to identify whether these ferrous objects had been produced by direct or indirect process.

In 2009 Blakelock et al.⁸8 Blakelock E, Martinón-Torres M, Veldhuijzen VH, Young T. Slag inclusions in iron objects and the quest for provenance: an experiment and a case study. Journal of Archaeological Science. 2009;36(8):1745-1757. analyzed several specimens from bloom to forged products, which were produced by T. Young (Museum of Welsh Life, Wales Parents) between 1998 and⁹9 Crew P. The experimental production of Prehistoric bar iron. Historical Metallurgy. 1991;25:21-36. 2004 from a series of ore reduction experiments. In these experiments, Young recreated the direct reduction and forging processes used by the prehistoric population near Cardiff to produce iron artefacts⁹9 Crew P. The experimental production of Prehistoric bar iron. Historical Metallurgy. 1991;25:21-36.. Additionally, the authors⁸8 Blakelock E, Martinón-Torres M, Veldhuijzen VH, Young T. Slag inclusions in iron objects and the quest for provenance: an experiment and a case study. Journal of Archaeological Science. 2009;36(8):1745-1757. compared the chemical composition of the slag inclusions of ferrous artifacts from two different archaeological sites (X century, Jordan; and 900BC, Israel). They investigated and analyzed various bivariate graphs of the chemical compositions of the slag inclusions in order to establish their process signatures. The authors demonstrated that the use of these bivariate graphs was not precise to establish the signatures of the investigated processes - even for samples which were experimentally produced - due to the extensive number of processing variables interfering in the final chemical composition of the slag inclusions.

In 2009 Desaulty et al.¹⁰10 Desaulty AM, Dillmann P, L'Heritier M, Mariet C, Gratuze B, Joron JL, et al. Does it come from the Pays de Bray? Examination of an origin hypothesis for the ferrous reinforcements used in French medieval churches using major and trace element analyses. Journal of Archaeological Science. 2009;36(10):2445-2462. examined few hypotheses about the origins of iron reinforcements, which were sampled from French medieval churches. They used the chemical analysis results of the major elements found in the slag inclusions along with the analyses of trace elements in order to investigate 32 ferrous artifacts from the cathedrals of Beauvais and Roven and 14 ferrous parts from archaeological sites near the Bray Pays region (located between the cities of Beauvais and Roven and famous for the production of iron by indirect process during the fifteenth century). Their results indicated that the trace elements could only be used to identify the provenance of ferrous artifacts produced by direct process. The authors rejected the hypothesis that the iron samples taken of the cathedrals of Beauvais and Roven had been produced in the Bray Pays region.

In 2012 Charlton et al.¹¹11 Charlton MF, Blakelock E, Martinón-Torres M, Young T. Investigating the production provenance of iron artifacts with multivariate methods. Journal of Archaeological Science. 2012;39(7):2280-2293. analyzed the same samples, investigated by Blakelock et al.⁴4 Zequini A. Arqueologia de uma fábrica de ferro: Morro de Araçoiaba, séculos XVI-XVIII. [PhD Thesis]. São Paulo: Museu de Arqueologia e Etnologia, Universidade de São Paulo; 2006. 223 p., but they applied a new methodology for analyzing the results of EDX microanalysis of the slag inclusions, using only the amounts of Al₂O₃, SiO₂, K₂O, CaO, TiO₂ and MnO in the slag inclusions. They used multivariate method and hierarchical clusters analysis in order to separate and identify the provenance within the production process (for instance, bloomery slag, fuel ash, clay or smithing flux) of the various slag inclusions found in the ferrous samples. They applied the same methodology to investigate the provenance of various ferrous artifacts from Scandinavia using previous results¹²12 Buchwald VF, Wivel H. Slag Analysis as a Method for the Characterization and Provenancing of Ancient Iron Objects. Materials Characterization. 1998;40(2):73-96. and the authors were able to successfully identify three clusters of samples, representing the production sites of Denmark, Norway and Sweden.

In 2014 Disser et al.¹³13 Disser A, Dillmann P, Bourgain C, L'Héritier M, Vega E, Bauvais S, et al. Iron reinforcements in Beauvais and Metz Cathedrals: from bloomery or finery? The use of logistic regression for differentiating smelting processes. Journal of Archaeological Science. 2014;42:315-333. investigated the slag inclusions of 60 ferrous pieces sampled from Gothic monuments of Beauvais Cathedral (Picardie, France) and Mutte Tower Metz Cathedral (Lorraine, France). They applied "logistic regression" to distinguish ferrous pieces produced by direct and indirect process and used the multivariate method to determine the signature of the production process of the artifacts collected in the French Gothic cathedrals.

Maia et al.¹⁴14 Maia RR, Dias SM, Azevedo CRF, Landgraf FJG. Archaeometry of ferrous artefacts from Luso-Brazilian archaeological sites near Ipanema River, Brazil. REM, Revista Escola de Minas. 2015;68(2):187-193.

15 Maia RR. Análise de inclusões de escória em amostras arqueológicas da fábrica de ferro de Ipanema. [MEng. Dissertation]. São Paulo: Escola Politécnica, Universidade de São Paulo; 2014. 209 p.^-¹⁶16 Maia RR, Azevedo CRF, Landgraf FJG. Análise de inclusões de escória em amostras da fábrica de ferro de Ipanema. In: 67º Congresso ABM Internacional; 2012 Jul 31 - Ago 3; Rio de Janeiro, RJ, Brazil. investigated by EDX microanalysis the slag inclusions of ferrous objects collected from the Royal Iron Factory of São João de Ipanema and Afonso Sardinha archaeological site. The authors questioned the effectiveness of the linear regression method (passing through the origin), which had been proposed by Dillmann and L'Héritier⁷7 Dillmann P, L'Héritier M. Slag inclusion analyses for studying ferrous alloys employed in French medieval buildings: supply of materials and diffusion of smelting processes. Journal of Archaeological Science. 2007;34(11):1810-1823. to determine the signature of the production processes, but they did not investigate other methodologies¹⁰10 Desaulty AM, Dillmann P, L'Heritier M, Mariet C, Gratuze B, Joron JL, et al. Does it come from the Pays de Bray? Examination of an origin hypothesis for the ferrous reinforcements used in French medieval churches using major and trace element analyses. Journal of Archaeological Science. 2009;36(10):2445-2462.^-¹¹11 Charlton MF, Blakelock E, Martinón-Torres M, Young T. Investigating the production provenance of iron artifacts with multivariate methods. Journal of Archaeological Science. 2012;39(7):2280-2293.^,¹³13 Disser A, Dillmann P, Bourgain C, L'Héritier M, Vega E, Bauvais S, et al. Iron reinforcements in Beauvais and Metz Cathedrals: from bloomery or finery? The use of logistic regression for differentiating smelting processes. Journal of Archaeological Science. 2014;42:315-333. to obtain the signature of the production processes of Ipanema and Sardinha. They suggested that the presence of higher contents of TiO₂ in the inclusions was a typical characteristic of the artifacts collected in Sardinha's archaeological site.

The main purpose of the present investigation is to test a new methodology, which uses SEM microscopy and EDX microanalysis of the main microconstituents found in the microstructure of the slag inclusions (such as the "matrix" and the wüstite phase) - instead of merely using the average microanalysis of the "entire" multiphase inclusions¹¹11 Charlton MF, Blakelock E, Martinón-Torres M, Young T. Investigating the production provenance of iron artifacts with multivariate methods. Journal of Archaeological Science. 2012;39(7):2280-2293.- to correctly separate the ferrous artifacts of four different origins (Ipanema, Sardinha, Missões and Bahia) by hierarchical cluster analysis of these microanalysis results.

2. Materials and methods

2.1. Samples

The analyzed samples are part a collection of objects, which are currently stored in the Laboratory for Microstructural Characterization Hubertus Colpaert (Polytechnic School, University of São Paulo, Brazil). The identification and description of the samples used in the present investigation are shown in Table 1. The samples from the Royal Factory of São João de Ipanema were collected at the Geological Collection of the National Museum (Rio de Janeiro, Brazil) from iron bars, which the director of the Royal Factory, Colonel Mursa, had bestowed to the Brazilian Emperor, Dom Pedro II, in 1886. These artifacts were almost certainly produced using the Styrian refining method described by Ipanema's engineer, L. Dupré¹⁷17 Dupré L. Memória sobre a Fábrica de Ferro de São João do Ipanema. Annaes da Escola de Minas de Ouro Preto. 1885;4:37-67..

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Table 1
Identification, description and origin of the investigated ferrous samples

The sample of Sardinha is one of the various ferrous artifacts collected around the ruins of a site about two kilometers from Ipanema factory, which were almost certainly produced by direct process⁴4 Zequini A. Arqueologia de uma fábrica de ferro: Morro de Araçoiaba, séculos XVI-XVIII. [PhD Thesis]. São Paulo: Museu de Arqueologia e Etnologia, Universidade de São Paulo; 2006. 223 p..

The sample of Missões comes from the archaeological site of São João Batista Mission, in Rio Grande do Sul, Brazil⁵5 Zanettini PE, Camargo PFB. Arqueologia no Parque Fonte Missioneira: Programa de prospecções arqueológicas Parque Fonte Missioneira. São Miguel das Missões, Rio Grande do Sul. Relatório Final. São Paulo: Zanettini Arqueologia, Instituto de Patrimônio Histórico de Artístico; 2010. 142 p.. The Austrian Jesuit, Anton Sepp, described the furnaces which were constructed in the region of Missões to produce iron by direct process¹⁸18 Carle CB. Metalurgia nas Missões - uma introdução. [Master's Thesis]. Porto Alegre: Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS); 1993. 200 p., but there is still an uncertainty concerning the provenance of these ferrous artefacts⁵5 Zanettini PE, Camargo PFB. Arqueologia no Parque Fonte Missioneira: Programa de prospecções arqueológicas Parque Fonte Missioneira. São Miguel das Missões, Rio Grande do Sul. Relatório Final. São Paulo: Zanettini Arqueologia, Instituto de Patrimônio Histórico de Artístico; 2010. 142 p.: were they produced from local iron ore or imported from Europe?

The sample of Bahia was collected around 2010 from a railroad bridge located (Dom Pedro II) in the State of Bahia, Brazil. The bridge was built in 1885 using iron plates with the brand "Mossend" stamped on them. Mossend Iron and Steel Works were one of the largest producers of malleable iron in Scotland during the second half of the XIX century¹⁹19 Lewis J, Murdoch R. Excavations at Summerlee Ironworks, Coatbridge, North Lanarkshire. Proceedings of the Society of Antiquaries of Scotland. 2007;137:501-529., operating with two different refining methods: the puddling process and the reverberatory furnace process.

2.2. Microstructural characterization and EDX microanalysis

Microstructural characterization was carried out using light and scanning electron microscopy. The volumetric fractions of the slag inclusions were obtained by the image analysis of the unetched metallographic samples of approximately 20 fields at 100X magnification under light microscope using Image-Pro Plus (Media Cybernetics) software.

The microanalyses of the multiphase inclusions were carried out on the main microstructural constituents of the inclusion (the "matrix" and the wüstite phase) and on an larger area representing the "entire" multiphase inclusion, in a total of 480 microanalyses (at least 60 regions of the slag inclusion were analyzed for each sample). The authors recognize that the "matrix" of the inclusions is multiphasic, but the microanalyses of these other phases were omitted in the present work. The authors used, instead, larger microanalysis areas to obtain the mean values of the chemical microanalysis of the "matrix" of the inclusions.

Microanalyses were carried out in a JEOL JSM-6300 scanning electron microscope equipped with a Noran EDX detector and using the following parameters: working distance of 15 mm; voltage of 20 kV; acquisition time of 180 seconds; area mode; standardless mode; and ZAF correction. Additionally, a restriction for the quantitative chemical analyses was imposed by assuming that all the chemical elements present in the inclusions were in the form of oxides. These results generated various bivariate graphs, such as % SiO₂ versus %Al₂O₃; % CaO versus %K₂O; % Al₂O₃ versus %MgO; %FeO versus %SiO₂; and % TiO₂ versus %V₂O₅. Extra care was taken in the numerical interpretation of FeO content found in the slag inclusions, as the depths of the inclusions were not precisely known and some "contribution" of Fe of the matrix could occur, slightly increasing the intensity of the Fe peaks during the EDX microanalyses of "thin" slag inclusions and, consequently, the amount of FeO in inclusions with a depth below 1 µm. Therefore, inclusions larger than 5 µm were regularly selected for the EDX microanalyses.

2.3. Hierarchical cluster analysis

Multivariate method and hierarchical cluster analysis were applied using a critical set of variables for each type of microanalysis results: the entire multiphase inclusions, the matrix of the inclusions; and the wüstite phase of the inclusions. After data treatment, preliminary cluster analysis was applied to detect the outliers, which were excluded from the analysis so the critical sets of oxides could be identified for each type of microanalysis (entire multiphase inclusions, the matrix of the inclusions and the wüstite phase). Common transformations were then used to apply equal weights to the results within the critical sets of oxides, such as standardization and log-ratio transformations, and these results were grouped by the Ward method²⁰20 Johnson RA, Wichern DW. Applied multivariate statistical analysis. Sixth edition. London: Pearson Education Inc; 2007. 767 p.. The parameter of similarity for the definition of clusters adopted in the present work was the Euclidean distance and the data was statistically analyzed by using version 1.16.03 Statgraphics Centurion XVI software (StatPoints Technologies Inc. 1982 - 2010). The results of the hierarchical cluster analysis method were displayed in dendrograms, which were used to identify four clusters. These clusters were analyzed in order to assess the efficacy of the grouping for each set of microanalysis results (entire multiphase inclusions, the matrix of the inclusions and the wüstite phase).

3. Results

Table 1 features the volumetric fraction of slag inclusions in all samples, which can be divided into two groups of results. The samples of Ipanema showed values near 1%, while the remaining samples showed values of volumetric fraction of slag inclusions above 4%.

Typical results of microstructural characterization of the slag inclusions are shown in Figures 1-a to 1-d. In general, these inclusions presented a complex microstructure with the presence of dendrites wustita (FeO) in a multiphase matrix.

Figure 1
Typical microstructure of slag inclusions, featuring the presence of dendrites of wüstite, BEI, SEM: (a) Ipanema (Ip-135 sample); (b) Bahia (sample B-45); (c) Missions (M-123 sample); (d) Sardinha (S-107 sample).

The average results of EDX microanalysis of the entire multiphase inclusions are shown in Table 2 for basic comparison, indicating high relative values for the standard deviation, as the chemical composition of each inclusion depends on its provenance within the production processing, such as bloomery smelting, bloom refining and artifact production; along with the chemical composition of the ore, furnace lining, fuels, fluxes and hearth lining⁸8 Blakelock E, Martinón-Torres M, Veldhuijzen VH, Young T. Slag inclusions in iron objects and the quest for provenance: an experiment and a case study. Journal of Archaeological Science. 2009;36(8):1745-1757.^,¹¹11 Charlton MF, Blakelock E, Martinón-Torres M, Young T. Investigating the production provenance of iron artifacts with multivariate methods. Journal of Archaeological Science. 2012;39(7):2280-2293.. All samples, however, featured FeO content above 60%. The highest contents of V₂O₅ in the inclusions were found for the samples of Ipanema and Sardinha sites. The latter also presented inclusions with the highest contents of MgO, K₂O and TiO₂, while the samples of Ipanema showed the highest contents of P₂O₅. Finally the sample of Missões presented inclusions with the highest content of SiO₂ and the sample of Bahia presented the highest MnO content.

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Table 2
Average EDX microanalysis results of the "entire" multiphase slag inclusions.

Four typical bivariate graphs (% SiO₂ versus %Al₂O₃; % CaO versus % K₂O; %Al₂O₃ versus % MgO; and % FeO versus %SiO₂) of the values of EDX microanalyses of the entire multiphase inclusions are shown in Figures 2-a to 2-d. These results featured the usual scattering, not allowing the accurate grouping of the samples by visual cluster analysis in accordance with their provenance, confirming previous results ¹⁴14 Maia RR, Dias SM, Azevedo CRF, Landgraf FJG. Archaeometry of ferrous artefacts from Luso-Brazilian archaeological sites near Ipanema River, Brazil. REM, Revista Escola de Minas. 2015;68(2):187-193.

15 Maia RR. Análise de inclusões de escória em amostras arqueológicas da fábrica de ferro de Ipanema. [MEng. Dissertation]. São Paulo: Escola Politécnica, Universidade de São Paulo; 2014. 209 p.^-¹⁶16 Maia RR, Azevedo CRF, Landgraf FJG. Análise de inclusões de escória em amostras da fábrica de ferro de Ipanema. In: 67º Congresso ABM Internacional; 2012 Jul 31 - Ago 3; Rio de Janeiro, RJ, Brazil.. Figures 2-a (%SiO₂ versus %Al₂O₃) and 2-b (%CaO versus %K₂O), for instance, showed the best results in terms of clustering, suggesting the existence of four distinct groups of results, which were in agreement with their provenance. Figure 2-c to 2-d, however, did now allow the correct identification of four distinct clusters.

Figure 2
Typical bivariate graphs showing the amount of oxides in the "entire" multiphase slag inclusions: (a) %SiO₂ versus %Al₂O₃; (b) %CaO versus %K₂O; (c) %Al₂O₃ versus % MgO; and d) %FeO versus %SiO₂.

Table 3 shows the average EDX microanalysis of the matrix of the microstructure of the slag inclusions for basic comparison. The matrix presented lower amounts of FeO (usually bellow 60%) and lower standard deviations than those found for the entire multiphase inclusions (see Table 2). The samples of Ipanema, except for the IP-135 sample, showed lower contents of SiO₂, K₂O, Al₂O₃, MnO, TiO₂, MgO and CaO; and higher content of P₂O₅ when compared to the sample of Sardinha. The IP-135 (Ipanema) sample showed results, which were similar to the values found for the S-107 (Sardinha) sample. Finally, the sample of Bahia presented the highest values of Al₂O₃ and MnO, while the sample of Sardinha presented the lowest values of FeO and the highest values of MgO, SiO₂, K₂O and CaO.

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Table 3
Average EDX microanalysis results of the matrix of the slag inclusions

The average EDX microanalyses results of the wüstite phase in the slag inclusions are shown in Table 4 for basic comparison. The wüstite phase presented higher FeO contents, usually above 90%. The relative values of the standard deviations were higher than the ones found for matrix of the microstructure of the inclusions (see Table 3), probably due to the dilution of the non-ferrous oxides. The samples of Ipanema and Sardinha featured, however, the highest values of V₂O₅ content, while the sample of Missões featured the lowest content of CaO and the highest contents of P₂O₅ and SiO₂. The sample of Bahia featured the highest values of MnO and Al₂O₃, while the samples of Bahia and Missões presented the highest Al₂O₃ contents. Finally, the sample of Sardinha presented the highest values of V₂O₅, TiO₂ and MgO.

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Table 4
Average EDX microanalysis results of the wüstite phase of the slag inclusions

The bivariate graph of TiO₂ versus V₂O₅ in the wüstite phase is shown in Figure 3, indicating different clusters for the samples of Bahia and Missões. The graph also indicated a significant intersection for the results of Sardinha and Ipanema, which did not allow the separation of these results into two different clusters. Figure 3 suggests, however, that the inclusions of the sample of Sardinha tend to have higher contents of V₂O₅ and TiO₂ in the wüstite phase than the samples of Ipanema.

Figure 3
Bivariate graph showing the amount of oxides (%TiO₂ versus %V₂O₅) in the wüstite phase of the slag inclusions.

After a critical examination of all EDX results, the authors applied the multivariate method and hierarchical cluster analysis ¹⁰10 Desaulty AM, Dillmann P, L'Heritier M, Mariet C, Gratuze B, Joron JL, et al. Does it come from the Pays de Bray? Examination of an origin hypothesis for the ferrous reinforcements used in French medieval churches using major and trace element analyses. Journal of Archaeological Science. 2009;36(10):2445-2462.^,²⁰20 Johnson RA, Wichern DW. Applied multivariate statistical analysis. Sixth edition. London: Pearson Education Inc; 2007. 767 p. for the 480 microanalysis results (the entire multiphase inclusions, the matrix of the inclusions and the wüstite phase), using different sets of critical variables for each group of results (see Table 5). The resulting dendrograms - featuring a dotted line which separated the results into fours clusters - are shown in Figures 4 to 6.

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Table 5
Characteristic components present in the slag inclusions, including their main microconstituents (matrix and wüstite), for each group of samples

Figure 4
Dendrogram using the treated EDX results of the entire multiphase slag inclusions.

Figure 5
Dendrogram using the treated EDX results of the "matrix" of the slag inclusions.

Figure 6
Dendrogram using the treated EDX results of the wüstite phase of the slag inclusions.

4. Discussion

4.1 Inclusion microanalysis versus production processing of iron parts

All investigated samples have a large volume fraction of slag inclusions (see table 1), indicating that none of them were produced in the XX century, which could indicate a possible contamination during the sampling of the sites. The sample of Bahia showed a large volumetric fraction of slag inclusions (~6%), suggesting that the Scottish iron plates material used to build the railway bridge in Bahia were produced by puddling. By contrast, the samples of Ipanema showed a much lower volumetric fraction of slag inclusions (~1%), which was related to the exceptional expertise on the control of the Styrian process, which was introduced in the Royal Iron Factory of São João de Ipanema by a group of Austrian ironworkers¹⁷17 Dupré L. Memória sobre a Fábrica de Ferro de São João do Ipanema. Annaes da Escola de Minas de Ouro Preto. 1885;4:37-67..

The microstructure the "matrix" of the slag inclusions was typically more complex than the description used in the present work (see Figures 1-a to 1-d), being usually composed by the eventual presence of fayalite (2FeO.SiO₂) phase in a glassy phase¹⁵15 Maia RR. Análise de inclusões de escória em amostras arqueológicas da fábrica de ferro de Ipanema. [MEng. Dissertation]. São Paulo: Escola Politécnica, Universidade de São Paulo; 2014. 209 p.. All samples showed the presence of dendritic wustite (FeO) phase inside the slag inclusions, which is compatible with the high FeO content in the inclusions (Table 2). These values were similar to the values observed in the archaeometallurgical literature⁷7 Dillmann P, L'Héritier M. Slag inclusion analyses for studying ferrous alloys employed in French medieval buildings: supply of materials and diffusion of smelting processes. Journal of Archaeological Science. 2007;34(11):1810-1823.

8 Blakelock E, Martinón-Torres M, Veldhuijzen VH, Young T. Slag inclusions in iron objects and the quest for provenance: an experiment and a case study. Journal of Archaeological Science. 2009;36(8):1745-1757.

9 Crew P. The experimental production of Prehistoric bar iron. Historical Metallurgy. 1991;25:21-36.

10 Desaulty AM, Dillmann P, L'Heritier M, Mariet C, Gratuze B, Joron JL, et al. Does it come from the Pays de Bray? Examination of an origin hypothesis for the ferrous reinforcements used in French medieval churches using major and trace element analyses. Journal of Archaeological Science. 2009;36(10):2445-2462.

11 Charlton MF, Blakelock E, Martinón-Torres M, Young T. Investigating the production provenance of iron artifacts with multivariate methods. Journal of Archaeological Science. 2012;39(7):2280-2293.

12 Buchwald VF, Wivel H. Slag Analysis as a Method for the Characterization and Provenancing of Ancient Iron Objects. Materials Characterization. 1998;40(2):73-96.

13 Disser A, Dillmann P, Bourgain C, L'Héritier M, Vega E, Bauvais S, et al. Iron reinforcements in Beauvais and Metz Cathedrals: from bloomery or finery? The use of logistic regression for differentiating smelting processes. Journal of Archaeological Science. 2014;42:315-333.

14 Maia RR, Dias SM, Azevedo CRF, Landgraf FJG. Archaeometry of ferrous artefacts from Luso-Brazilian archaeological sites near Ipanema River, Brazil. REM, Revista Escola de Minas. 2015;68(2):187-193.

15 Maia RR. Análise de inclusões de escória em amostras arqueológicas da fábrica de ferro de Ipanema. [MEng. Dissertation]. São Paulo: Escola Politécnica, Universidade de São Paulo; 2014. 209 p.^-¹⁶16 Maia RR, Azevedo CRF, Landgraf FJG. Análise de inclusões de escória em amostras da fábrica de ferro de Ipanema. In: 67º Congresso ABM Internacional; 2012 Jul 31 - Ago 3; Rio de Janeiro, RJ, Brazil.. High FeO content in the slag is usually associated with the oxidizing conditions in the refining step of the indirect process, when the high carbon content of the pig iron must be oxidized. It is somehow surprising that high FeO contents were observed for the samples of Sardinha and Missões, which were produced in more reducing conditions (direct process).

The relatively high SiO₂ content observed in the slag inclusions, especially in the "matrix" (see Table 3), is rather common, as the addition of SiO₂ is known to decrease the melting point of the slag and increase its fluidity during processing¹⁵15 Maia RR. Análise de inclusões de escória em amostras arqueológicas da fábrica de ferro de Ipanema. [MEng. Dissertation]. São Paulo: Escola Politécnica, Universidade de São Paulo; 2014. 209 p.. Phosphorous oxide was also present in all samples, especially in the matrix of the inclusions (Table 3). Dillmann et al.⁷7 Dillmann P, L'Héritier M. Slag inclusion analyses for studying ferrous alloys employed in French medieval buildings: supply of materials and diffusion of smelting processes. Journal of Archaeological Science. 2007;34(11):1810-1823. indicated that the phosphorous content of the artifacts produced by the indirect process tended to be higher than the ones produced by the direct process. Table 3 indicated that the sample of Sardinha (produced by direct process) featured P₂O₅ content below 10%, while most of the samples of Ipanema (likely produced by indirect process) presented P₂O₅ content higher than 17% (except for Ip-135 sample, which presented P₂O₅ content around 7%). The sample of Bahia (produced by indirect process) showed a P₂O₅ content of 13%, which is the same content observed for the samples of Missões (likely produced by direct process). These results suggested that the P₂O₅ content of the matrix of the slag inclusions cannot be used as a single variable to identify the type of processing of the ferrous artifacts.

The presence of TiO₂ in the slag inclusions of the samples of Ipanema and Sardinha was predominantly concentrated in the wüstite phase (see Tables 2 to 4). This observation was consistent with the amount of Ti (~ 3% Ti) found in the local magnetitic iron ore of the Araçoiaba Hill²¹21 Guarino V, Azzone RG, Brotzu P, Gomes CB, Melluso L, Morbidelli L, et al. Magmatism and fenitization in the Cretaceous potassium-alkaline-carbonatitic complex of Ipanema, São Paulo State, Brazil. Mineralogy and Petrology. 2012;104(1):43-61.. Iron ores with high Ti content are usually attributed to magmatic origins²²22 Marsden RW. Iron ore exploration and geology. In: Kennedy BA, ed. Surface Mining. Englewood: Society for Mining, Metallurgy and Exploration; 1990., which is the case of the carbonatite of the Araçoiaba hill. By contrast, TiO₂ was not observed in the wüstite phase of the sample of Missões, which is in agreement with previous work²³23 Hüttner E, Hüttner EA, Oliveira GBV, Vivian DL, Dedavid BA. Caracterização metalográfica de uma cruz metálica da cidade de Camaquã (RS). Revista Liberato. 2015;16(26):177-191.. Hüttner and co-workers²³23 Hüttner E, Hüttner EA, Oliveira GBV, Vivian DL, Dedavid BA. Caracterização metalográfica de uma cruz metálica da cidade de Camaquã (RS). Revista Liberato. 2015;16(26):177-191. investigated the slag inclusions of ferrous artifacts from the site of Missões and observed the presence of Ti in the wüstite phase only for one sample from a total of four. It is not absolutely certain, however, whether the ferrous objects collected in the archaelogical site of Missões were produced from local iron ore or imported from Europe⁵5 Zanettini PE, Camargo PFB. Arqueologia no Parque Fonte Missioneira: Programa de prospecções arqueológicas Parque Fonte Missioneira. São Miguel das Missões, Rio Grande do Sul. Relatório Final. São Paulo: Zanettini Arqueologia, Instituto de Patrimônio Histórico de Artístico; 2010. 142 p..

Vanadium was found in the wüstite phase of all samples, although the samples of Ipanema and Sardinha presented the highest values of V₂O₅ (see Table 4). Figure 3 indicated that the inclusions of the sample of Sardinha tend to present higher contents of V₂O₅ and TiO₂ in the wüstite phase than the samples of Ipanema. Most of the literature, however, did not mention the presence of V in the slag inclusions⁷7 Dillmann P, L'Héritier M. Slag inclusion analyses for studying ferrous alloys employed in French medieval buildings: supply of materials and diffusion of smelting processes. Journal of Archaeological Science. 2007;34(11):1810-1823.

8 Blakelock E, Martinón-Torres M, Veldhuijzen VH, Young T. Slag inclusions in iron objects and the quest for provenance: an experiment and a case study. Journal of Archaeological Science. 2009;36(8):1745-1757.

9 Crew P. The experimental production of Prehistoric bar iron. Historical Metallurgy. 1991;25:21-36.

10 Desaulty AM, Dillmann P, L'Heritier M, Mariet C, Gratuze B, Joron JL, et al. Does it come from the Pays de Bray? Examination of an origin hypothesis for the ferrous reinforcements used in French medieval churches using major and trace element analyses. Journal of Archaeological Science. 2009;36(10):2445-2462.^-¹¹11 Charlton MF, Blakelock E, Martinón-Torres M, Young T. Investigating the production provenance of iron artifacts with multivariate methods. Journal of Archaeological Science. 2012;39(7):2280-2293.^,¹³13 Disser A, Dillmann P, Bourgain C, L'Héritier M, Vega E, Bauvais S, et al. Iron reinforcements in Beauvais and Metz Cathedrals: from bloomery or finery? The use of logistic regression for differentiating smelting processes. Journal of Archaeological Science. 2014;42:315-333., only Buchwald ¹²12 Buchwald VF, Wivel H. Slag Analysis as a Method for the Characterization and Provenancing of Ancient Iron Objects. Materials Characterization. 1998;40(2):73-96. observed its presence. The samples of Ipanema and Sardinha presented V₂O₅ contents higher than TiO₂ (see Table 4 and Figure 3), although the chemical analysis of the iron ore of the Araçoiaba hill showed the opposite proportion between V and Ti (3% Ti and 0.45% V). Additionally, there is a geological evidence that magmatic iron ores usually contain proportionally higher content of Ti than V²²22 Marsden RW. Iron ore exploration and geology. In: Kennedy BA, ed. Surface Mining. Englewood: Society for Mining, Metallurgy and Exploration; 1990.. This question will be answered by future microstructural and chemical analyses of samples of the pig iron, the blast furnace slag and the refining slag of Ipanema available in the Geological Collection of the National Museum in Rio de Janeiro. Finally, the amounts of TiO₂, V₂O₅ and MnO in the wüstite phase of the sample of Bahia sample suggests that the iron ore of the Mossend Iron and Steel Works contained significant amounts of Ti, Mn and V.

4.2. Hierarchical cluster analysis

Multivariate method and hierarchical cluster analysis were applied using a critical set of variables and outliers for each family of microanalysis results (see Table 5 and Figures 4 to 6). The dendrogram using the treated EDX results of the entire multiphase slag inclusions and a set of critical variables defined by P₂O₅, MgO, SiO₂, K₂O, CaO, TiO₂ and Al₂O₃ (see Figure 4) showed that the four clusters (for a Euclidean distance of approximately 400) were not correctly related to their sites. The third cluster, for instance, contained slag inclusions from three different sites. The dendrogram using the treated EDX results of the matrix of the slag inclusions and a set of critical variables defined by CaO, P₂O₅, K₂O, TiO₂ and Al₂O₃ (see Figure 5) showed the same behavior. Only the dendrogram using the results of the wüstite phase (see Figure 6) and a set of critical oxides defined by MgO, Al₂O₃, V₂O₅, MnO and TiO₂ allowed the accurate separation and precise grouping of the samples of each one of the investigated sites (Sardinha, Ipanema, Bahia and Missões) for a Euclidean distance of approximately 300.

The choice of the critical set of oxides and the detection of the outliers were important stages of the hierarchical cluster analysis, which depended on the careful examination and data treatment of all 480 EDX results²⁰20 Johnson RA, Wichern DW. Applied multivariate statistical analysis. Sixth edition. London: Pearson Education Inc; 2007. 767 p.. In the present investigation, four clusters could be identified in all dendrograms, but only the dendrogram for the wüstite phase (see Figure 6) allowed the separation of the samples into four clusters effectively representing the four production sites of Missões, Bahia, Ipanema and Sardinha.

The most important features in the present work compared to previous investigation¹¹11 Charlton MF, Blakelock E, Martinón-Torres M, Young T. Investigating the production provenance of iron artifacts with multivariate methods. Journal of Archaeological Science. 2012;39(7):2280-2293. were the use of the microanalysis results of the wüstite phase and the inclusion of the MnO and V₂O₅ contents in the critical set of variables (see Table 5). Charlton et al.¹¹11 Charlton MF, Blakelock E, Martinón-Torres M, Young T. Investigating the production provenance of iron artifacts with multivariate methods. Journal of Archaeological Science. 2012;39(7):2280-2293., for instance, used during the cluster analysis a set of critical variables with six oxides (MgO, Al₂O₃, SiO₂, CaO and TiO₂) and their microanalyses were representative of the whole volume of the slag inclusions. The new methodology used in the present investigation should be statistically verified with regard to the number of samples and production sites. Hierarchical cluster analysis was a reliable tool to separate the groups of samples, but the number of the distinct groups of samples in the present investigation was well known. When this number is not known, the choice of the Euclidian distance to define the number of clusters can be a rather subjective matter¹¹11 Charlton MF, Blakelock E, Martinón-Torres M, Young T. Investigating the production provenance of iron artifacts with multivariate methods. Journal of Archaeological Science. 2012;39(7):2280-2293.^,²⁰20 Johnson RA, Wichern DW. Applied multivariate statistical analysis. Sixth edition. London: Pearson Education Inc; 2007. 767 p..

4.3 A new approach to the history of the Royal Iron Factory of São João de Ipanema

The historian Paulo Araújo²⁴24 Araújo PEM. Historian. Personal communication. 2016 May 22nd. stated that there are evidences of the use of good process practices concerning the ironmaking at the Royal Iron Factory of São João de Ipanema, contradicting a significant body of Brazilian literature²⁵25 Calógeras JP. A Fábrica de Ferro de São João de Ipanema. Revista Brasileira. 1895;1.

26 Gomes FAM. História da siderurgia no Brasil. São Paulo: EDUSP, 1983.^-²⁷27 Alfonso-Goldfarb AM, Ferraz MHM. A institucionalização da metalurgia no Brasil: da Escola à Praxis. Revista da Sociedade Brasileira da História da Ciência. 1992;7:15-24.. His statement was based on at least three pieces of evidences: firstly the paper¹⁷17 Dupré L. Memória sobre a Fábrica de Ferro de São João do Ipanema. Annaes da Escola de Minas de Ouro Preto. 1885;4:37-67. written by L. Dupré (Ipanema engineer) and published in 1885 at the Journal of the School of Mines of Ouro Preto, which described the technical operation of the Ipanema factory in great detail. Additionally, this paper cited relevant international references to the subject, indicating the familiarity of the engineers of Ipanema with the technological aspects of the ironmaking process, including the Styrian process of decarburizing the pig iron (~4%C). Karsten's and Tunner's books²⁸28 Karsten CJB. Handbuch für Eisenhüttenkunde. Berlin: Reimer; 1841.^-²⁹29 Tunner P. Die Stabeisen- und Stahlbereitung in Frischherden, oder, der Wohlunterrichtete Hammermeister. Freiberg: Engelhardt; 1858., which were mentioned in this paper, were vital bibliography in the field of ironmaking for most of the XIX century. Finally, the Ipanema factory had a well established library on ironmaking since 1810 mostly based on Swedish and German literature²⁸28 Karsten CJB. Handbuch für Eisenhüttenkunde. Berlin: Reimer; 1841.

29 Tunner P. Die Stabeisen- und Stahlbereitung in Frischherden, oder, der Wohlunterrichtete Hammermeister. Freiberg: Engelhardt; 1858.^-³⁰30 Landgraf FJG, Araújo PEM. A arquitetura do alto-forno e a biblioteca perdida de Ipanema: técnica e conhecimento no Brasil Joanino. In: Anais Eletrônicos do 14º Seminário Nacional de História da Ciência e da Tecnologia; 2012 Out 8 - 11; Belo Horizonte, MG, Brasil. p. 1-15..

"The process employed at Ipanema for the transformation of pig iron in wrought iron is the same used in Leoben, High Styria, here imported by the refining workmen hired in that part of Austria. This process differs significantly in some points from that described by Karsten in his treaty on metallurgy, under the designation of Styrian process. Today's forge at Ipanema is similar to one working in Reichenau, about which P. Tunnner writes in his book."

The low volume fraction of slag inclusions of Ipanema's bars shown in the present paper (see Table 1) can be another piece of evidence, confirming the idea of Paulo Araújo about the use of good processing practices in the factory of Ipanema. The superior quality of its ferrous products, specially the ductility, had been attested by a report published in 1883 by a railroad company³¹31 Relatório da Diretoria da Companhia Paulista. Document available at the library of the Museu da Companhia Paulista, Jundiaí, Brazil; 1883.. The fact that no other blast furnaces were built in Brazil up to 1888 should be an important topic for economic historians. Market size, logistics, competition from imports and lack of capital could explain the situation in the beginning of the XIX century, but not after the coffee boom wealth allowed the railroad expansion in the State of São Paulo.

Archaeometallurgical investigations can greatly improve our understanding of the history and our culture by improving our awareness of our technological development³²32 Wayman ML. Archaeometallurgical contributions to a better understanding of the past. Materials Characterization. 2000;45(4-5):259-267.. The technological aspects of the processing of metallic products can be partially deciphered by the microstructural characterization of these artifacts associated with the collection and interpretation of historical documentation³²32 Wayman ML. Archaeometallurgical contributions to a better understanding of the past. Materials Characterization. 2000;45(4-5):259-267.

33 Piaskowski J. Metallographic investigations of ancient iron objects from the territory between the Oder and the basin of the Vistula River. The Journal of the Iron and Steel Institute. 1961;98:263-282.

34 Williams AR. Slag inclusions in armour. Journal of Historical Metallurgical Society. 1991;24:69-80.

35 Boniardi M, Gariboldi E, Vedani M. Metallographic studies on an ancient Roman nail. Metallurgical Science and Technology. 1992;10:28-38.

36 Pense AW. Iron through the ages. Materials Characterization. 2000;45(4-5):353-363.

37 Light JD. Observations concerning the hand forging of wrought iron. Materials Characterization. 2000;45(4-5):327-340.

38 Ehrhardt KL, Nash SK, Swann CP. Metal-forming practices among the seventeenth century Illinois, 1640-1682. Materials Characterization. 2000;45(4-5):275-288.

39 Jakielski KE, Notis MR. The metallurgy of Roman medical instruments. Materials Characterization. 2000;45(4-5):379-389.

40 Angelini E, Grassini S, Solorzano G, Campos GN, de Caro T. Integrated approach to the characterization of artifacts of the Brazilian colonial period. Applied Physics A, Materials Science & Processing. 2006;83(4):485-491.^-⁴¹41 Campos GN, Solorzano GI. Microanalytical study of a ferrous agricultural tool recovered from a historical site in Rio de Janeiro. Applied Physics A, Materials Science & Processing. 2004;79(2):315-318.. Our ability to accurately reply to all the cultural, commercial and technological questions is, indeed, very limited (either by sampling or lack of documentation) but there are few investigators eager to apply microstructural characterization techniques to, somehow, elucidate the history of technology, the dating of objects, the spread of technologies and the nature and implications of the contact between different cultures³²32 Wayman ML. Archaeometallurgical contributions to a better understanding of the past. Materials Characterization. 2000;45(4-5):259-267..

5. Conclusions

EDX microanalyses of the entire multiphase inclusions and their microconstituents of ferrous artifacts - Royal Iron Factory of São João de Ipanema, D. Pedro II Bridge (Bahia, Brazil and produced in Scotland) and archaeological sites of São Miguel de Missões (Rio Grande do Sul, Brazil) and Afonso Sardinha (São Paulo, Brazil) - were carried out but these results, which were organized as bivariate graphs, were not capable to successfully separate the four groups of samples according to their provenance.
The bivariate graph of TiO₂ versus V₂O₅ in the wüstite phase effectively distinguished two clusters for the samples of Bahia and Missões, but could not separate the results from Ipanema and Sardinha. The suggested, however, that the Sardinha's inclusions tend to feature higher contents of V₂O₅ and TiO₂ than the inclusions of Ipanema's samples.
Titanium and vanadium content in the wüstite crystals inside the slag inclusions are a promising reference for obtaining the chemical signature of wrought iron samples of Ipanema and Sardinha.
The dendrogram with the microanalysis results of the wüstite phase (using as critical variables the contents of MnO, MgO, Al₂O₃, V₂O₅ and TiO₂) allowed the identification of four clusters, which successfully represented the samples of the four production sites (Ipanema, Sardinha, Missões and Bahia).
The average volume fraction of slag inclusions observed in the samples of Ipanema (~1%) suggested the presence of fine technological expertise on the control of the indirect process of the Royal Iron Factory of São João de Ipanema.

6. Acknowledgments

F. J. G. Landgraf and C. R. F. Azevedo would like to thank the National Council for Scientific and Technological Development (CNPq) for the research grant. The authors also would like to express their gratitude to the Historian P. E. M. Araújo (Institute of Geosciences, Unicamp, Brazil); to Prof. R. Ramos and Mr. R. A. Azevedo (Museu Nacional, Rio de Janeiro, Brazil); to Dr.-Ing. A. H. Feller; to Prof. B. Dedavid and Prof. E. Hüttner (both from the Pontifícia Universidade Católica, Rio Grande do Sul, Brazil); to MEng. M. F. Moreira and Dr. T. Yonamine (Institute for Technological Research); to Prof. Dr. A. C. Neiva, MEng. R. R. Maia, Mr. V. Santos and Prof. T. N. Bittencourt. (Polytechnic School, University of São Paulo); and to Mr. L. B. Regalado (Floresta Nacional de Ipanema, Instituto Chico Mendes de Conservação da Biodiversidade, Ministério do Meio Ambiente do Brazil). Finally, the authors dedicate this work to the memories of Prof. M. D. Andreatta, whose pioneer work on the Ipanema site allowed the collection and preservation of significant historical artifacts, and Mr. A. C. Azevedo.

7. References

¹
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²
Santos NP. A fábrica de ferro São João de Ipanema: economia e política nas últimas décadas do segundo reinado (1860-1889). [Master's Dissertation]. São Paulo: Faculdade de Filosofia, Letras e Ciência Humanas, Universidade de São Paulo; 2009. 180 p.
³
Landgraf FJG, Araújo PEM, Schroeder R. Ipanema e os alemães. In: Martius-Staden-Jahrbuch, 61. São Leopoldo: Oikos; São Paulo: Instituto Martius-Staden; 2016. In Press.
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Zequini A. Arqueologia de uma fábrica de ferro: Morro de Araçoiaba, séculos XVI-XVIII [PhD Thesis]. São Paulo: Museu de Arqueologia e Etnologia, Universidade de São Paulo; 2006. 223 p.
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Zanettini PE, Camargo PFB. Arqueologia no Parque Fonte Missioneira: Programa de prospecções arqueológicas Parque Fonte Missioneira. São Miguel das Missões, Rio Grande do Sul Relatório Final. São Paulo: Zanettini Arqueologia, Instituto de Patrimônio Histórico de Artístico; 2010. 142 p.
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Marques AC, Borges AR, Bittencourt TN. Evaluation and modelling of wrought iron bridge in Bahia. In: Chen A, Frangopol DM, Ruan X, eds. Bridge Maintenance, Safety, Management and Life Extension Boca Raton: CRC Press; 2014. p. 334-339.
⁷
Dillmann P, L'Héritier M. Slag inclusion analyses for studying ferrous alloys employed in French medieval buildings: supply of materials and diffusion of smelting processes. Journal of Archaeological Science 2007;34(11):1810-1823.
⁸
Blakelock E, Martinón-Torres M, Veldhuijzen VH, Young T. Slag inclusions in iron objects and the quest for provenance: an experiment and a case study. Journal of Archaeological Science 2009;36(8):1745-1757.
⁹
Crew P. The experimental production of Prehistoric bar iron. Historical Metallurgy 1991;25:21-36.
¹⁰
Desaulty AM, Dillmann P, L'Heritier M, Mariet C, Gratuze B, Joron JL, et al. Does it come from the Pays de Bray? Examination of an origin hypothesis for the ferrous reinforcements used in French medieval churches using major and trace element analyses. Journal of Archaeological Science 2009;36(10):2445-2462.
¹¹
Charlton MF, Blakelock E, Martinón-Torres M, Young T. Investigating the production provenance of iron artifacts with multivariate methods. Journal of Archaeological Science 2012;39(7):2280-2293.
¹²
Buchwald VF, Wivel H. Slag Analysis as a Method for the Characterization and Provenancing of Ancient Iron Objects. Materials Characterization 1998;40(2):73-96.
¹³
Disser A, Dillmann P, Bourgain C, L'Héritier M, Vega E, Bauvais S, et al. Iron reinforcements in Beauvais and Metz Cathedrals: from bloomery or finery? The use of logistic regression for differentiating smelting processes. Journal of Archaeological Science 2014;42:315-333.
¹⁴
Maia RR, Dias SM, Azevedo CRF, Landgraf FJG. Archaeometry of ferrous artefacts from Luso-Brazilian archaeological sites near Ipanema River, Brazil. REM, Revista Escola de Minas 2015;68(2):187-193.
¹⁵
Maia RR. Análise de inclusões de escória em amostras arqueológicas da fábrica de ferro de Ipanema [MEng. Dissertation]. São Paulo: Escola Politécnica, Universidade de São Paulo; 2014. 209 p.
¹⁶
Maia RR, Azevedo CRF, Landgraf FJG. Análise de inclusões de escória em amostras da fábrica de ferro de Ipanema. In: 67º Congresso ABM Internacional; 2012 Jul 31 - Ago 3; Rio de Janeiro, RJ, Brazil.
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Dupré L. Memória sobre a Fábrica de Ferro de São João do Ipanema. Annaes da Escola de Minas de Ouro Preto 1885;4:37-67.
¹⁸
Carle CB. Metalurgia nas Missões - uma introdução [Master's Thesis]. Porto Alegre: Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS); 1993. 200 p.
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Lewis J, Murdoch R. Excavations at Summerlee Ironworks, Coatbridge, North Lanarkshire. Proceedings of the Society of Antiquaries of Scotland 2007;137:501-529.
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Johnson RA, Wichern DW. Applied multivariate statistical analysis Sixth edition. London: Pearson Education Inc; 2007. 767 p.
²¹
Guarino V, Azzone RG, Brotzu P, Gomes CB, Melluso L, Morbidelli L, et al. Magmatism and fenitization in the Cretaceous potassium-alkaline-carbonatitic complex of Ipanema, São Paulo State, Brazil. Mineralogy and Petrology 2012;104(1):43-61.
²²
Marsden RW. Iron ore exploration and geology. In: Kennedy BA, ed. Surface Mining Englewood: Society for Mining, Metallurgy and Exploration; 1990.
²³
Hüttner E, Hüttner EA, Oliveira GBV, Vivian DL, Dedavid BA. Caracterização metalográfica de uma cruz metálica da cidade de Camaquã (RS). Revista Liberato 2015;16(26):177-191.
²⁴
Araújo PEM. Historian Personal communication. 2016 May 22^nd
²⁵
Calógeras JP. A Fábrica de Ferro de São João de Ipanema Revista Brasileira 1895;1.
²⁶
Gomes FAM. História da siderurgia no Brasil São Paulo: EDUSP, 1983.
²⁷
Alfonso-Goldfarb AM, Ferraz MHM. A institucionalização da metalurgia no Brasil: da Escola à Praxis. Revista da Sociedade Brasileira da História da Ciência 1992;7:15-24.
²⁸
Karsten CJB. Handbuch für Eisenhüttenkunde Berlin: Reimer; 1841.
²⁹
Tunner P. Die Stabeisen- und Stahlbereitung in Frischherden, oder, der Wohlunterrichtete Hammermeister Freiberg: Engelhardt; 1858.
³⁰
Landgraf FJG, Araújo PEM. A arquitetura do alto-forno e a biblioteca perdida de Ipanema: técnica e conhecimento no Brasil Joanino. In: Anais Eletrônicos do 14º Seminário Nacional de História da Ciência e da Tecnologia; 2012 Out 8 - 11; Belo Horizonte, MG, Brasil. p. 1-15.
³¹
Relatório da Diretoria da Companhia Paulista Document available at the library of the Museu da Companhia Paulista, Jundiaí, Brazil; 1883.
³²
Wayman ML. Archaeometallurgical contributions to a better understanding of the past. Materials Characterization 2000;45(4-5):259-267.
³³
Piaskowski J. Metallographic investigations of ancient iron objects from the territory between the Oder and the basin of the Vistula River. The Journal of the Iron and Steel Institute 1961;98:263-282.
³⁴
Williams AR. Slag inclusions in armour. Journal of Historical Metallurgical Society 1991;24:69-80.
³⁵
Boniardi M, Gariboldi E, Vedani M. Metallographic studies on an ancient Roman nail. Metallurgical Science and Technology 1992;10:28-38.
³⁶
Pense AW. Iron through the ages. Materials Characterization 2000;45(4-5):353-363.
³⁷
Light JD. Observations concerning the hand forging of wrought iron. Materials Characterization 2000;45(4-5):327-340.
³⁸
Ehrhardt KL, Nash SK, Swann CP. Metal-forming practices among the seventeenth century Illinois, 1640-1682. Materials Characterization 2000;45(4-5):275-288.
³⁹
Jakielski KE, Notis MR. The metallurgy of Roman medical instruments Materials Characterization 2000;45(4-5):379-389.
⁴⁰
Angelini E, Grassini S, Solorzano G, Campos GN, de Caro T. Integrated approach to the characterization of artifacts of the Brazilian colonial period. Applied Physics A, Materials Science & Processing 2006;83(4):485-491.
⁴¹
Campos GN, Solorzano GI. Microanalytical study of a ferrous agricultural tool recovered from a historical site in Rio de Janeiro. Applied Physics A, Materials Science & Processing 2004;79(2):315-318.

Publication Dates

Publication in this collection
24 Nov 2016
Date of issue
Jan-Feb 2017

History

Received
11 June 2016
Reviewed
13 Aug 2016
Accepted
08 Sept 2016

This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Sample	Origin	Volume fraction of slag inclusions	Description of the objects and dimensions
Ip-130	Royal Iron Factory of São João de Ipanema (São Paulo, Brasil), Geological Collection of the National Museum (Rio de Janeiro, Brazil)	1.6 ± 0.5	Rectangular bar (cross section of 10 x 4 mm and length of 100 mm)
Ip-131	Royal Iron Factory of São João de Ipanema (São Paulo, Brasil), Geological Collection of the National Museum (Rio de Janeiro, Brazil)	1.2 ± 0.4	Round bar (diameter of 8 mm and length of 100 mm)
Ip-133	Royal Iron Factory of São João de Ipanema (São Paulo, Brasil), Geological Collection of the National Museum (Rio de Janeiro, Brazil)	0.7 ± 0.5	Square bar (cross section of 12 x 12 mm and length of 100 mm)
Ip-134	Royal Iron Factory of São João de Ipanema (São Paulo, Brasil), Geological Collection of the National Museum (Rio de Janeiro, Brazil)	1.3 ± 0.8	Square bar (cross section of 17 x 17 mm and length of 100 mm)
Ip-135	Royal Iron Factory of São João de Ipanema (São Paulo, Brasil), Geological Collection of the National Museum (Rio de Janeiro, Brazil)	1.2 ± 0.6	Square bar (cross section of 22 x 22 mm and length of 100 mm)
B-145	Dom Pedro II Bridge (Bahia, Brazil and produced in Scotland)	6 ± 2	Sample of the bridge (plate of approximately 400 x 200 mm and thickness of ~ 20 mm)
M-123	Archaeological site of São Miguel de Missões (Rio Grande do Sul, Brazil)	7 ± 3	Nail (larger cross section of 3 x 3 mm and length of 50 mm)
S-107	Archaeological site of Afonso Sardinha (São Paulo, Brazil), Prof. M. Andreatta's collection	4 ± 1	Nail (larger cross section of 15 x 15 mm and length of 100 mm)

Sample	MgO	SiO₂	P₂O₅	K₂O	CaO	TiO₂	V₂O₅	MnO	Al₂O₃	FeO
Ip-130	0.4±0.5	6±6	9±9	0.4±0.4	5±5	0.4±0.3	1.2±0.6	0.6±0.4	0.1±0.1	78±17
Ip-131	0.5±0.3	10±5	16±7	0.5±0.5	5±5	0.5±0.5	2±2	0.8±0.4	0.1±0.1	64±12
Ip-133	0.5±0.3	8±6	10±8	0.4±0.3	6±4	0.5±0.5	2±2	0.6±0.2	0.1±0.1	73±16
Ip-134	0.3±0.3	5±4	15±9	0.2±0.2	2±2	0.3±0.3	0.9±0.7	0.5±0.3	0.1±0.1	77±9
Ip-135	0.6±0.3	12±12	5±5	0.6±0.5	12±12	0.6±0.3	0.9±0.6	0.5±0.3	0.2±0.2	71±27
B-145	0.1±0.1	10±4	8±6	0.1±0.1	0.2±0.2	0.6±0.3	0.3±0.2	2±1	1.6±0.5	77±9
M-123	0.6±0.5	19±16	10±6	1±1	4±3	0.1±0.3	0.2±0.2	0.6±0.4	1.5±1.3	63±18
S-107	1.1±0.3	15±6	5±4	2±1	9±4	0.9±0.5	2±1	1.3±0.3	0.6±0.3	64±12

Sample	MgO	SiO₂	P₂O₅	K₂O	CaO	TiO₂	V₂O₅	MnO	Al₂O₃	FeO
Ip-130	0.6±0.2	10±7	22±9	0.8±0.6	9±5	0.1±0.1	0.1±0.1	0.7±0.2	0.2±0.2	57±7
Ip-131	1.0±0.4	18±3	17±4	0.9±0.6	9±6	0.1±0.1	0.1±0.1	1.0±0.1	0.2±0.2	53±8
Ip-133	0.8±0.2	17±5	19±5	0.9±0.7	10±6	0.1±0.1	0.1±0.1	0.8±0.2	0.3±0.3	52±8
Ip-134	0.9±0.3	16±4	17±4	0.8±0.7	7±4	0.1±0.1	0.1±0.1	0.9±0.2	0.2±0.2	58±6
Ip-135	0.8±0.3	24±7	7±5	1.1±0.6	14±8	0.4±0.3	0.2±0.2	0.8±0.4	0.6±0.3	51±12
B-145	0.1±0.1	18±4	13±6	0.1±0.1	0.4±0.3	0.2±0.2	0.1±0.1	3.4±0.7	2±1	63±2
M-123	0.4±0.0	17±2	13±3	0.8±0.1	4.2±0.3	0.1±0.1	0.1±0.1	0.5±0.1	0.7±0.3	64±5
S-107	1.4±0.3	25±5	9±4	2.3±0.9	15±5	0.4±0.2	0.2±0.2	1.5±0.3	0.9±0.4	45±8

Sample	MgO	SiO₂	P₂O₅	CaO	TiO₂	V₂O₅	MnO	Al₂O₃	FeO
Ip-130	0.2±0.2	0.4±0.2	0.1±0.1	0.1±0.1	0.5±0.2	1.7±0.6	0.3±0.2	0.1±0.1	97±1
Ip-131	0.1±0.1	0.6±0.3	0.2±0.2	0.2±0.2	1.0±0.3	3.0±0.6	0.4±0.2	0.1±0.1	95±1
Ip-133	0.2±0.2	0.3±0.1	0.1±0.1	0.1±0.1	0.3±0.2	1.5±0.6	0.1±0.2	0.1±0.1	98±1
Ip-134	0.1±0.1	0.5±0.5	0.8±0.8	0.1±0.1	0.5±0.4	2.0±0.7	0.2±0.2	0.1±0.1	96±2
Ip-135	0.2±0.1	0.3±0.1	0.1±0.1	0.1±0.1	0.6±0.3	1.6±0.9	0.4±0.1	0.1±0.1	97±2
B-145	0.1±0.1	0.8±0.3	0.1±0.1	0.1±0.1	0.9±0.1	0.5±0.2	0.9±0.4	0.5±0.1	96±1
M-123	0.1±0.1	3±2	4±3	0.3±0.3	0.1±0.1	0.3±0.2	0.1±0.1	0.6±0.3	92±5
S-107	0.4±0.2	0.9±0.4	0.1±0.1	0.3±0.2	1.2±0.3	3.2±0.9	0.7±0.1	0.1±0.1	93±1

Group of samples	Entire slag inclusions	Matrix	Wüstite phase
Ipanema	P₂O₅, CaO and V₂O₅	P₂O₅	TiO₂ and V₂O₅
Bahia	MnO and Al₂O₃	MnO and Al₂O₃	Al₂O₃ and MnO
Missões	SiO₂ and Al₂O₃	Al₂O₃	SiO₂, P₂O₅ and Al₂O₃
Sardinha	MgO, K₂O, TiO₂ and V₂O₅	MgO, SiO₂, K₂O, TiO₂ and Al₂O₃	MgO, TiO₂ and V₂O₅
Critical set of oxides used for the cluster analysis	P₂O₅, MgO, SiO₂, K₂O, CaO, TiO₂ and Al₂O₃	CaO, P₂O₅, K₂O, TiO₂ and Al₂O₃	MgO, Al₂O₃, V₂O₅, MnO and TiO₂
Detected outliers	V₂O₅, Cr₂O₃ and MnO	MgO, SiO₂, V₂O₅, Cr₂O₃ and MnO	SiO₂, P₂O₅, K₂O, CaO and Cr₂O₃