Rimas VisGirda on mon 23 nov 09
I use a number of AMACO Velvets to cone 3-4 and sometimes to cone 10. Some =
colors remain true, some change (usually for the worst). I have found that =
since AMACO has gone completely lead-free, some of the colors I use are beh=
aving differently -mostly some seem to start to flux at a lower temperature=
; which matters for me as I usually don't glaze over the color, but shouldn=
't matter if you put a glaze over the color. Another factor might be the in=
gredients of the (c/6) affecting the ingredients of the underglaze -more te=
sting here... And some colors (by name) are somewhat different than they us=
ed to be...
When I started using the Velvets, mostly for workshops, I did tests (cone 3=
-10) on the colors that I intended to use and just stuck with those that wo=
rked. Now that everything is lead-free, I'll need to retest and maybe find =
substitute colors for my needs. I don't think that the firing cycle affects=
the color formation, although the atmosphere might. I suggest running some=
tests, especially if the underglazes were recently purchased.
I don't think this problem is limited to AMACO, as all the companies (Dunca=
n, Mayco, etc) are going lead free if they haven't already. And the reformu=
lation of overglazes, underglazes, and glazes will result in minor or major=
differences from what we have been used to. In my work I use a lot of over=
glazes and find that the new formulations aren't what I'm used to in many c=
ases -sometimes worse but sometimes better, better especially in the stabil=
ity of the reds...
-Rimas
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