The surface defect appeared mainly as air bubbles and ferroferric oxide drops which centred around the lower outer - field portion of the stoneware cup.
The fact that early American stoneware is bound up with industrial slavery, a lesser-known model than the agricultural kind, may be news to visitors at a major exhibition of David Drake's jars.
So we are going to go outside now, go get some even bigger reactions, with the alkali metals. This is a dog bowl which is stoneware, it is very hard, not likely to break, unless I drop it on my toes.