Lime Blue - A Mediaeval Pigment for Wall Paintings?

The rediscovery of a mixed calcium copper hydroxide as a blue pigment is described. The pigment, named lime blue, has not yet been reported in the chemical literature. The formula CaCu(OH) 4 ·H 2 O was found from a single-crystal X-ray structural analysis. The pigment is simple to prepare according...

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Bibliographic Details
Published in:Studies in conservation 2003-01, Vol.48 (3), p.171-182
Main Authors: Krekel, Christoph, Polborn, Kurt
Format: Article
Language:English
Subjects:
Acetates
Calcium
Chlorides
Copper
Eggshells
Excavation and methods
Flasks
Laboratory methods
Methodology and general studies
Physical and chemical analysis
Pigments
Prehistory and protohistory
Quaternary ammonium compounds
Vinegars
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Summary:The rediscovery of a mixed calcium copper hydroxide as a blue pigment is described. The pigment, named lime blue, has not yet been reported in the chemical literature. The formula CaCu(OH) 4 ·H 2 O was found from a single-crystal X-ray structural analysis. The pigment is simple to prepare according to historical recipes for the production of synthetic blue pigments. The recipes are based on an original that is included in the 'Mappae Clavicula' and probably of southern English origin. Lime blue is only stable in aqueous binders and in wall paintings. To date, no evidence of the pigment has been found. Further pigments detected in the products of the historical recipes for lime blue are calumetite, Cu(Cl,OH) 2 2·H 2 O and calcium copper acetate, CaCu(CH 3 COO) 4 ·6H 2 O.
ISSN:0039-3630
2047-0584
DOI:10.1179/sic.2003.48.3.171