underglazes White engobe under underglaze

[Sprakeloos 1]

Dear all,

I am fairly new to ceramics and have revived my interest due to forced staying at home here in the Netherlands. It's provided a means for me to stay positive in the midst of such much somberness.

I've been working with a deep black firing cone 6 stoneware and want to do some bright and colorful underglaze decorations without a clear cover glaze (as I like the mattness of the unglazed surface). I've noticed how direct application of Amaco velvet underglazes (even 3 thick coats) on this clay results in muted colors as the black clay bleeds through to some extent. I happen to have a Cone 6 engobe rich in tin oxide sitting around. Is there any reason I couldn't use a thin coat of this engobe under the Velvets to provide a white background for the colors to pop? Or will the tin oxide potentially react adversely with the stains in the underglaze and alter their colors?

I am grateful for any advice

Best,

Joris

[Callie Beller Diesel 2,711]

Putting a white slip over the black clay is a good plan. However you may find the tIn reacts with some of the green colours to turn pink. You’d have to test to find out which ones. If you have any zircon based opacifier, that would be less reactive. Although even a slip with no added opacifier could be of help as long as it’s made from a lighter coloured clay.