Pigment traces on medieval stonework in Gotland’s churches – examination of seven 12th century baptismal fonts and a limestone pew Anders G. Nord et al. http://kulturarvsdata.se/raa/fornvannen/html/2016_017 Fornvännen 2016(111):1 s. 17-26 Ingår i samla.raa.se Art. Nord et al 17-26_Layout 1 2016-02-15 16:52 Sida 17 Pigment traces on medieval stonework in Gotland’s churches –examination of seven 12th century baptismal fonts and a limestone pew By Anders G. Nord, Kate Tronner, Kjell Billström and Marianne Gustafsson Belzacq Nord, A.G., Tronner, K., Billström, K. & Gustafsson Belzacq, M., 2016. Pigment traces on medieval stonework in Gotland's churches – examination of seven 12th century baptismal fonts and a limestone pew. Fornvännen 111. Stockholm. The authors have analysed pigments on eight medieval stone objects in Gotland’s churches. They are seven 12th century baptismal fonts made of sandstone and a ce­ remonial limestone pew in Burs church from about 1350. Fragments of medieval paint were sampled and analysed by SEM/EDX, FTIR, GC­MS and MC­ICP­MS. 57 samples were collected. Infinitesimal traces of cinnabar, ultramarine and gold foil were sparsely found. Iron oxide (Fe2O3) and lead pigments occur commonly, while green and blue pigments seem less frequent. Later “improvements” of green copper arsenites were found on the limestone pew in Burs church. Lime has prima­ rily been used as a binding medium, possibly in combination with now complete­ ly degraded organic substances. Isotope analyses indicate that the lead pigments most likely have a provenance in the Harz and Erzgebirge mountains in Germany, possibly also in Eisleben. Other pigments have more remote origins, which reflects Visby’s significance as a trade center. Anders G. Nord, Kevingeringen 10, SE–182 50 Danderyd [email protected] Kate Tronner, Flädergränd 2, SE–187 73 Täby [email protected] Kjell Billström, Department of Geosciences, Swedish Museum of Natural History, Box 50007, SE–104 05 Stockholm [email protected] Marianne Gustafsson Belzacq, Gurpe 117 Kräklingbo, SE–623 70 Katthammarsvik [email protected] Hundreds of medieval churches in Sweden have present study, we analysed original paint traces more or less well­preserved murals painted al secco from seven 12th century baptismal fonts made on lime ground. We have earlier documented and from sandstone and a ceremonial limestone pew analysed many of their pigments (Nord et al. 1996; from around 1350, all in Gotland’s churches, by 2000; 2011; 2015), and have so far identified 23 means of SEM/EDX and other techniques. The pigments (disregarding modern ones used for later aim of the study has been to identify pigments of “improvements”). Recently, we have extended our variousshadesandsearch forbindingmedia. While studies to include medieval stonework such as the stone itself is obviously of local origin, we have outdoor portals (Nord & Tronner 2014). For the tried to identify the origin of the pigments. Fornvännen 111 (2016) Art. Nord et al 17-26_Layout 1 2016-02-15 16:52 Sida 18 18 Anders G. Nord et al. Fig. 1. The sandstone font in Barlingbo church, Got­ land, with a sculpture of the archangel Gabriel. Pho­ to: Bengt A. Lundberg, National Heritage Board of Sweden. seems to have been the most productive. Roos­ val’s invented name Byzantios suggests a Russian­ Byzantine origin, but this has so far not been generally accepted by art historians. Presumably the name was suggested (Roosval 1918) by a cer­ tain stylistic elegance influenced by Byzantine murals. Sixteen fonts on Gotland, some of them in poor condition, have been attributed to Byzan­ tios. For the present study, the Hejde and Hogrän fonts were selected, rather from the presence of usable original paint than as typical representa­ tives of the Byzantios group. Another sculptor named Hegvald or Hegwaldr was in all likeli­ hood a local man from Gotland. His workshop has a more popular and provincial style, and Gotland has 92 well­preserved medieval stone three fonts were selected for this study, namely churches, in addition to ruined ones. Most of these those of Endre, Etelhem and Stånga. The Etel­ churches have a medieval baptis­mal font, made hem font is actually signed “Hegwaldr” in runes. from sandstone or limestone from local quarries. The Majestatis group, famous for their extreme Most fonts have been painted, and original paint skill in reliefs, is represented here by the font of can still be observed as infinitesimal traces. How­ Gerum. Roosval assigned this name because of ever, many fonts were re­decorated 300–400 years the group's habit of representing Christ as sover­ ago, which strongly reduced the number of eign ruler of the world (Majestatis domini). Final­ usable objects for the present study. ly, the Master of Barlingbo is only known to have Nearly a century ago, art historian Johnny made the font in Barlingbo church (fig. 1). This Roosval (1918; 1925) identified a number of sculp­ beautiful and imposing font is the largest one on tors or workshops, and named them Byzantios, the island. Majestatis, Hegvald, Calcarius, Sigraf, Egypticus All seven selected fonts have beautiful sculp­ etc. Many of these artisans seem to have worked tural decoration. The local sandstone they are made on Lund Cathedral before moving to the pros­ of consists mainly of quartz grains cemented to­ perous island of Gotland to work there. In his gether by calcium carbonate. The ceremonial pew 2012 survey of Gotland fonts, Svenrobert Lund ­ in Burs church however is made of local fine­ quist attributes each of 45 baptismal fonts to a grained limestone. It is probably a product of the specific group based on type, motif, decorations, Egypticus workshop. All paint traces for the study reliefs, chisels used, etc. These fonts include the were carefully sampled and documented. Many ones selected for the present study, and we use pigments could not be observed with the naked the attributions suggested by Roosval and Lund­ eye, but demanded a magnifying glass. When­ quist. It should also be added that the influential ever possible, we took somewhat larger samples Byzantine art of the same era in Sweden has been with the aim to search for binding media. In total discussed by for instance Andreas Lindblom & we collected 57 samples. Gunnar Svahnström (1959), Erland Lagerlöf (1999) and Svetlana Vasilyeva (2009). Among the sculptors, the Byzantios group Fornvännen 111 (2016) Art. Nord et al 17-26_Layout 1 2016-02-15 16:52 Sida 19 Pigment traces on medieval stonework in Gotland’s churches 19 SEM/EDX analyses of the pigments and minium transforms to (usually) black platt­ Work began some years earlier with Kate Tron­ nerite (e.g. Giovannoni et al. 1990; Nord et al. ner identifying the pigments on the Barlingbo 1996). This transformation may be partial or font by means of wet chemistry and X­ray pow­ complete. In the former case the colour may der diffraction (XRD). All other pigment sam­ become dark brown or a mixture of dark shades. ples were analysed by SEM/EDX, i.e. with a scan­ This process seems to be slow as any rapid change ning electron microscope (Hitachi S­4300) equip­ to black candle flames and haloes on the murals ped with a LINK/Oxford unit for X­ray micro­ would have evoked a congregation’s righteous analysis, at the Swedish Museum of Natural His­ anger. The transformation process requires O2(g) tory. from the air as oxidizing agent. Co­author M.G.B., Tab. 1 lists the results of the pigment analy­ with a life­long experience of medieval murals, ses. The pigments identified accord well with has noted that minium can retain its red colour in those found on medieval stone portals (Nord & cavities covered and protected by plaster. Tronner 2014), although gold and ultramarine We have also found that sometimes the oxi­ were never found there. Tab. 2 offers further che­ dation does not take place in paintings on other mical and mineralogical data. The pigment PbO substrates. A striking example is found in the is denoted as massicot, whether from the natural church of Härkeberga in Uppland. In the narrow mineral or a synthetic product with that compo­ staircase leading to the organ loft, there is an sition. Furthermore, plattnerite (β­PbO2) is not image from around 1490 of a man, originally paint­ an original pigment but a product of the oxidation ed with minium to wear orange clothes. Part of of a lead pigment. Chlorine was detected in many the painting is on lime ground where plattnerite samples, probably representing remains of mod­ has formed, another part on oak timber where ern cleaning agents. On the Burs pew, “improve­ the minium is preserved (Nord & Tronner 2000). ments” of copper arsenites were found. These are Moreover, lead pigments on wood from the likelytorepresentSchweinfurtergreenandScheele’s (long­since demolished) medieval stave church of green, as judged from the Cu:As atomic ratios. Dalhem on Gotland still preserve their original Tab. 3 lists the pigments we found on the colour (Nord & Tronner 2011). fonts and the pew. Note that pigments that are Our study of the baptismal fonts yielded a now missing from an individual object may orig­ similar result. Plattnerite has almost always form­ inally have been there. Iron oxide was found on ed when lime is present (tab. 1). Thus it seems that most of the fonts, and so was minium and lead lime, or some substance(s) therein, acts as a kind white. The coeval workshops Byzantios, Hegvald of catalyst for the oxidation process. The “platt­ and Majestatis, to which the examined fonts have nerite problem” has been discussed by other been attributed, seem to have used similar pa­ authors.