"Chris McBrien" wrote in message
. ..
PVA - I have used PVA glue diluted with water to seal the inside of a pot
that became porus. Just a desertspoon of PVA and add water so that it is
like milk. Pour this into the porus pot and swirl it around for a while.
Pour out the excess and just let it soak in and set.

Make sure you use exterior PVA not kids white PVA glue which will dissolve
again...