I use alumina in wax, similar recipe to Marcia's except I eyeball the amounts, on all lids. Generally on grogged clay bodies the surfaces are rough enough not to seal, but with low grog clay bodies and/or burnished galleries there can be some adhesion between the lid and the gallery. The alumina-wax is a reasonable countermeasure.
Kiln wash is not recommended as an alternative because it often contains both kaolin and silica, both of which are more likely to sinter together and adhere to the clay body. Alumina, by itself, does not.
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