Here's the results from some tests I did using a black glaze on the outside and a white glaze on the inside of some pieces, with various other glazes layered on top of the outside. The black glaze is a alberta slip glaze with cobalt oxide, hence all the blue showing up. The very runny glazes were layered with a glaze containing about 20 percent lithium carbonate, a strong flux. The picture at the bottom shows the result of Lithium melting down the white glaze inside, bringing some of the black glaze from the rim with it. The bottom picture is actually the same pot as the picture above it.
A day for planning
10 hours ago