Trouble with diy rock project

[wildroseofky]

I read all kinds of articles on people making their own rock formations with grout and styrofoam so I gave it a try. I just can't get the grout to stay on the styrofoam. I put about an 1/4 inch coating on it and let it dry for three days. When I picked it up, the grout chipped off in several places. It just cracked off. I am going to recover it with Portland cement and see if that works. I have tried several different Styrofoam shapes and the grout will not stay on it. Is there some trick to making it stick?

 

[tbrazil230]

Try going with thinner grout, just a bit thicker than water, and apply thin coats with a paint brush