In some cases I'm going to use terracotta pots for indoor plants, but also I'm going to use containers I've built myself -- small boxes with drainage, in which I'll have added a few worms.
Question: What is safe to use as a liner and sealant to waterproof those boxes.
I'd like to avoid plastic because it leaches. I don't trust glues generally, and I'm not sure about silicon either. Short of cooking up a big bowl of pine pitch in the back yard, for filling cracks and offering some protection for the wood, I'm stumped.
Thanks in advance for any opinions or advice.