Short answer: a 20 oz skinny tumbler (about 3 in across, 8 in tall) takes roughly 1.5 fl oz (45 ml) of mixed epoxy per coat; mix about 3 fl oz for two coats. A 30 oz tumbler takes about 2 fl oz per coat.
About 1.5 fl oz per coat, 3 fl oz for two coats, including drips.
Keep it spinning 6–8 hours or until it no longer moves, then let it cure 24–72 hours before washing by hand.
The coat is too thick or the epoxy is too thin. Use a tumbler-specific epoxy and spread thin coats.
See also: coaster & tumbler calculator · glitter & mica amounts
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