Expert: Leisha Hiester - 5/28/2009

Question
I have a problem with a under glaze that I'm using. It only happens with the black. It's a one stroke Chrysanthos in colbolt black. After I fire the greenware to cone 06 (porcelain clay by the way) I then find that the areas that I have used a decent amount of colour on transfers onto my glaze brush. I sometimes wipe over the bisque with a very lightly dampened sponge and it leaves a black residue on the sponge. Kind of like a floor that has been mopped with always leave a bit of a dirt stain on a clean mop.

I have contacted the supplier of this product and they can't tell me why it is happening and why it is only happening with the one colour. Have you come across this fault before.

I have tried firing to cone 05 and that didn't help any.

Thank you

Answer
Dear Kerry,
Have you tried firing your greenware to 04? Alot of underglazes are meant to apply on greenware. Have you checked your product whether it is to be used on greenware or bisque? Let me know if this helps and I'll investigate further. :) Leisha