Jeremy Osner Posted February 6, 2022 Report Share Posted February 6, 2022 21 hours ago, Michael_Molnar said: I’ll emphasize what others have said. Cochineal’s color is dependent on the metal used to make the lake, the pH of the mix used to precipitate the lake, and the pH of the medium in which it is mixed. The strong low pH (acid) of oil varnishes pulls the color red-side. However, the acidity can make the lake fugitive. This is a difficult balance to achieve. I love the colors of cochineal but avoid it because it is so temperamental. Everything I've been able to find to read online has supported this. If I decide to go any further beyond this current project, I'm sure I'll get Kirby et al's book. I'm going to follow Bursch's recipe for carmine lake, who says "The majority of the recipes for carmine,... differ but little from the above [Cenette's method] ; acid potassium tartrate is used instead of the oxalate [I'll be using cream of tartar], but the latter is to be preferred because of the slight solubility of the tartrate. It is important not to use too strong decoctions of cochineal, and to add only small quantities of alum" (I will likely err on the shy side with the tartar). He does not specify a quantity of alkali solution to use, and I'm thinking that's because you only should add a drop or 2 at a time, and let the dye bath foam up and recede, and then another few drops. My plan is to make 2l of dye bath from 40g ground cochineal, in two batches, one with 1/2 the tartar. I'll filter and divide those 1l batches in half and add a little less and a little more alum to each pair of containers. (All the recipes say to use shallow pans for precipitating the lake; Mason jars is what I have, fingers crossed that it will work with the relatively small amount of dye bath I'm making.) The jars are a quart capacity; It seems to me like that should work, knock on wood. Bursch says (if I'm reading it right) to add the alum to the simmering dye bath and simmer for another several minutes; but every other source I found seems to recommend dissolving the alum in boiling water and then adding it to the dye bath after filtering. I'm leaning toward adding the alum after filtering. Quote Link to comment Share on other sites More sharing options...
Michael_Molnar Posted February 6, 2022 Report Share Posted February 6, 2022 Keep us posted, Jeremy. I hope this is fun and fruitful. Quote Link to comment Share on other sites More sharing options...
Don Noon Posted February 7, 2022 Report Share Posted February 7, 2022 In a few days I'll be making some Michelman resin with cochineal. Stay tuned, as Mike says. Quote Link to comment Share on other sites More sharing options...
Don Noon Posted February 12, 2022 Report Share Posted February 12, 2022 On 2/6/2022 at 5:23 PM, Don Noon said: In a few days I'll be making some Michelman resin with cochineal. Stay tuned, as Mike says. Simplified, a base (KOH) was added to the cochineal to dissolve it, resulting in purple (as expected). Acid (HCl) was added to the precipitation phase to neutralize the base, giving a nice scarlet. However, in washing and filtering the resin, most of the red component washed out, giving a very purple resin. Useless, until purple violins become a huge fad. I'll stick with alizarin. It's cheaper, too. Quote Link to comment Share on other sites More sharing options...
Michael_Molnar Posted February 13, 2022 Report Share Posted February 13, 2022 6 hours ago, Don Noon said: Simplified, a base (KOH) was added to the cochineal to dissolve it, resulting in purple (as expected). Acid (HCl) was added to the precipitation phase to neutralize the base, giving a nice scarlet. However, in washing and filtering the resin, most of the red component washed out, giving a very purple resin. Useless, until purple violins become a huge fad. I'll stick with alizarin. It's cheaper, too. Alizarin is (arguably) the most stable of natural organic red pigments. (PR 83) Quote Link to comment Share on other sites More sharing options...
Don Noon Posted February 13, 2022 Report Share Posted February 13, 2022 11 hours ago, Michael_Molnar said: Alizarin is (arguably) the most stable of natural organic red pigments. (PR 83) But still extremely sensitive to Ph. Quote Link to comment Share on other sites More sharing options...
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