abs is rubbish a waste of money in my opinion,either wood or glass thats the way to go.good tip on the clay also thats a good idea .once the mould is made you can smooth it out a bit also and fill any small air holes left.a tip to stop air holes is shake the box and try to get the air out a little.a small vibrator also works dont know where you,ll find one of them
.we used to use a vibrating table when making plaster mouldings.the wifes washing machine on spin would also work!!!.
