Copper pigments

Kupfer-erz, n. copper ore. -fahlerz, n. tetrahe-drite tennantite. -farbe, /. copper color copper pigment. 

The usefulness of this kind of analysis is illustrated in Fig. 2.11 where the square wave voltammograms for azurite, smalt, and two samples from the frescoes painted by Palomino (1707) in the Sant Joan del Mercat church in Valencia (Spain) are shown. Copper pigments yield a unique stripping peak at —0.05 V, whereas cobalt pigments produce a main anodic peak at +0.02 V, accompanied by overlapping... 

Fig. 3.12 Tafel SL vs. 00 diagram for the most common copper pigments and copper alteration products. From SQWVs of specimen-modified paraffin-impregnated graphite electrodes immersed into 0.50 M phosphate buffer, pH 7.4. Potential scan initiated at -1-0.45 mV in the negative direction. Potential step increment 4 mV square wave amplitude 15 mV frequency 2 Hz...

Domenech A, Domenech-Carbo MT, Gimeno JV, Bosch F, Sauri MC, Casas MJ (2001) Electrochemical analysis using charge transfer coefficient/peak potential diagrams of the alteration in copper pigments from microsamples of baroque wall paintings attached to polymer film electrodes. Fresenius J Anal Chem 369 576-581. 

Domenech A, Domenech-Carbo MT, Edwards HGM (2008) Quantitation from Tafel analysis in solid-state voltammetry. Application to the study of cobalt and copper pigments in severely damaged frescoes. Anal Chem 80 2704-2716. 

These pigments almost always contain a considerable proportion of extraneous substances, either white (gypsum, kaolin, barium sulphate, etc.), or coloured (ochres, blacks), and in some instances they contain copper pigments or ultramarine. 

To overcome the restrictions of the Barium method, ammonium carbonate was, in some cases, replaced by anionic exchange resins that are less aggressive and enable the treatment of tempera even in the presence of copper pigments. It must be added that the reaction of anion exchange resins is restricted to the surface in contact with the resin. Furthermore, the first-stage transformation producing barium sulfate is left out and barium hydroxide is applied directly. This technique is convenient with the many restrictions imposed by preconsolidation by synthetic resins. 

Synonyms Arwood copper Bronze powder Cl 77400 Copper bronze Copper-milled Gold bronze Kafar copper Pigment metal 2 Raney copper... 

Hagadorn, A. (2004). An investigation into the use of blue copper pigments in European early printed books. American Institute for Conservation of Historic and Artistic Works, Book and Paper Group, Book and Paper Group Annual, 23, 41-55. 

The relative rarity of the mineral has led some authors to conclude that the symthetic analogue (copper chloride hydroxide, atacamite type, q.v.) was used as pigment and in fact there are mnnerous mediaeval recipes for preparing a green copper pigment with common salt. Of these perhaps the best known is that of Theophilus for viride sabum (q.v.). 

Mentioned in the Didlogos of the Spanish author Carducho (1633), according to Veliz (1986) it was probably a synthetic copper blue whose formation includes the formation of a crust (costra). Many copper pigments might potentially fit this description, however. 

---