Thank you talesoftrivia. So it ìs the bleached and purified stuff. I didn't know the chemistry word "Potassium bitartrate" . Always liked the word 'cream of tartar' that has nothing to do with cream at all. The Wiki article gives sufficient information.

"The crystals (wine diamonds) will often form on the underside of a cork in wine". "wine diamonds". Now that sounds really good. smile