Which should I use - Low, Mid, or High Fire Clay?

Hi there! At pottery supply store selling a low fire, mid fire and high fire Clay, which one should I use to mix mortar by your recipe? Thanx by advance!

You want to purchase the Mid or High Fire Clay…


Low Fire Clay - Very Porous / Not Waterproof

Mid Fire Clay - Excellent Bonding Properties / Waterproof

High Fire Clay - Excellent Bonding Properties / Waterproof