Hi everyone :) I want to make 10 x 2kg concrete pots that are 100% waterproof. They will be filled with water. I currently use a mix of: Portland cement Grey cement sand water Acrylic gripcure fibre 15% bonding liquid I sealed it twice with bonding liquid after curing. Should i seal the inside with clear paint, varnish or epoxy? Or is there an admixture that works?