Tuesday, May 08, 2007

Smalt Goes Grey

Apparently, I'm not the only one with this problem:

Plesters, Joyce

A preliminary note on the incidence of discolouration of smalt in oil media


Studies in conservation (1969) 14 pp 62-74

Although smalt, a glass, might be expected to behave as a stable pigment, discolouration of smalt-containing paint layers has been observed. Early references from the literature are cited which mention the discolouration of smalt in oil media. Originally blue layers on paintings have changed into dull grey or greyish-green. Experiments suggest the following factors for this discolouration: low refractive index of the pigment compared with that of oil media; interaction of alkali content or cobalt content with oil and oleo-resinous media; the possibility of similar reactions with resin-or oil-resin varnishes in certain conditions. Discolouration may also occur if smalt is mixed with other pigments, or added as a drier or as an adulterant. A proper understanding of the mechanism of the deterioration would require further research by more sophisticated methods.


Do I seem obsessed?

2 Comments:

Anonymous angelarae said...

I find this interesting. There seems to be some confusion as to whether smalt is gray or cobalt.

Ang

1:43 AM  
Blogger Anonyknits said...

Smalt is a very particular blue pigment, similar to Cobalt, but not precisely what people-who-are-into-colour mean when they say "Cobalt."

Apparently, though, Smalt degrades from deep blue to a grey under the right (wrong?) conditions.

So, I suppose that technically speaking it could be either.

But the photo of Sadie in Rowan 40 really looks quite blue to me.

Ah, well.

4:53 PM  

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