I installed cultured stone around a fireplace. I used regular mortar and applied directly to the backerboard without a scratch coat. Needless to say, the stone comes off the backerboard easily and cleanly leaving all the mortar still attached to the stone and a clean backerboard surface. after further reading, I see many suggestions to use thinset on th ebackerboard and mortar on the stone. Well, I am short on supplies and am wondering if I can use the stone that came off cleanly and just apply thinset or more mortar to th eback of the stone that already has dried mortar on it. I would creat a scratch coat on the backerboard with thinset before doing anything else.