cobalt turquoise

[Alexandra van Cruyningen]

:?: Does anyone have any experience with the pigment cobalt turquoise? I find it extremely difficult to grind and storing the paste is not possible as the pigment hardens underneath the water. Question is how do I grind this pigment and is it possible to store in a glass jar? I never had any problems grinding other pigments but this one....terrible.
Thanks for any advice
Alex

[Dennis H]

Alex,
I use a cobalt turquoise, but it gives me no problems at all. I only need to stir it thoroughly with a brush to temper it. (Yolk into dry pigment, adding a drop or two of water.) It dissolves almost instantly without any grinding, and leaves no grit. It is very fine, semi-transparent, and extremely vibrant. I don't have the packaging it came in, but I guess I probably bought it from Kremer.
I have other similar turquoise blues that are not cobalt, and they are difficult to work with: very coarse particles that have to be ground further to use with tempera. Almost as bad as verdigris. (One is labelled Ercolano blu, which I bought in a shop in Venice, IT, but I have no idea of its composition. The shop owner simply said, "minerali.")
Anyway, cobalt turquoise is a beautiful color. Perhaps try getting it from a different vendor?
Dennis

[turlogh]

Every once in a while, you get a bad batch. I've had no problems with cobalts.

[Alessandra Kelley]

I suppose it's the nature of pigments that they vary, even when chemically identical. I don't use Cobalt pigments, but I have had similar experiences with different batches of Ultramarine Blue: One batch solidified to something like rubber at the bottom of the jar; another stayed a slurry and never settled; one batch smelled like candy, another like a septic tank.

Coarse mineral blues might be Azurite, which is very gritty.

[Alexandra van Cruyningen]

Thank you, Dennis, Turlogh and Alessandra for your replies. Like you said Alessandra it is like rubber on the bottom of my jar. I will try another brand, seems a waiste though, as it was an expensive pigment. It is from Schminke. I'll try what Dennis said, just stir it with egg yolk and some water nd not try to store the paste. Had to throw the whole Jar out of the window (Fig.speaking I do bring my waste to chemical dump) because the rubber mess at the bottom was impossible to get out.
And yes, it is a beautiful colour. Used it on the dress of a little fairy. I will try to post the painting tomorrow in the critique section if I can manage. I am so terrible with computers and all these new technologies, but I'll try.
Alex.

[Alessandra Kelley]

I'm sorry you had to throw out your pigment. My "rubbery" Ultramarine was still usable -- I just had to use a *real* knife rather than a palette knife to get it out of the jar.