Eli5: Why do all my cups and glasses have rims on the bottom that collect water in the dishwasher?
In: Other
If it’s a ceramic cup, it needs a “foot” that does not have a coat of glaze so that it can be removed from the kiln after firing. If you look at any regular ceramic cup, the ring at the bottom of the cup, the “foot,” is unglazed and rough. If it had a coat of glaze, the glaze would melt and fuze to the kiln as it cooled. There are cups that have unglazed flat feet (not hard to make unlike people here suggest) but that unglazed, fired clay can absorb liquids (thus making it not dishwasher friendly), be rough to handle, and besides cups and bowls and other ceramic objects have had that traditional shape for millenia. Don’t know about glasses, but most glasses I own look like they have flat bottoms.
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