Here is a really good discussion of the different types of underglaze (and engobes).
I didn’t read the thing Christy put up, but it’s probably all you’d need. DMS doesn’t have any underglazes currently. We’ve got the iron oxide wash, and the cobalt wash, but those are slightly different from an underglaze.
The quick answer is that an “underglaze” doesn’t act like the glazes. They do stick to your pot, but usually not to the kiln.
I have it. Pouring one more head tonight and can bring it in tomorrow
You rock, thank you so much!
I placed it on the cart with a bunch of other molds