To be honest the mottled look was a bit of a mistake that worked. I was really impatient to pour the resin on and the green acrylic paint wasnt quite dry. I scuffed it a bit by pushing the stones around the tin. I went on to make a couple of tiny ponds using the indent bit on the bottom of a couple of beer cans. They didn't work quite so well as the resin isn't the clear variety and has a pink tinge. It would have been better if I had painted the bottoms with the green acrylic but heck... I am very new to this so have a lot to learn.