Expert: Debra Flint - 10/3/2011

Question
I have had problems with some of my underglazes (which may be several years old as I bought my business from another woman who'd had them a while), turning white and losing their color when fired. I put the adequate coats on and ensured it didn't rub off when I put the clear coat on. Is this a problem with ventilation in my kiln or is it possible that underglazes expire?

Thankyou for any help you can provide

Answer
Hi, Usualy undergalze does not go bad. It may be to thick but water is fine to thin. Were the bottles open? Did you fire at Cone 04 with a shelf check cone? Was the bisque clean off before glazing? Glaze fire at 06? There is alot of issues that could be the cause. Usually in the firing. Check your kiln with cone checks that sit on the shelves. Then test the glaze by self. Usually one of those, first. Good luck