Is air-dry clay waterproof?Updated a year ago

No, air-dry clay is not waterproof or food safe. Adding a layer of varnish makes it water resistant which is great for plant pots or other things that risk occasionally getting damp. Don't let that stop you from making vases or mugs though! Just use them to hold dried flower or pens. 

That said, the best way to make plant pots is to keep the plants in their own plastic pots which can be removed during watering and returned once excess water has drained out.