A few years ago I covered several styrofoam balls with hypertufa. They were small balls that were recycled from old Christmas ornaments, the kind with the satin thread around them. The balls were quite smooth and that made it difficult to get the hypertufa to stick, but I just kept squeezing & pressing until it stayed on. Looking back I think if I'd roughed up the surface it would've made my life much easier. Making the tufa stick to the bigger craft store variety (rough) styrofoam would probably be easier.

They look really neat, some of them I carved designs into the surface before they were completely set. The best part - they float! It really defies logic!

Hope that helps.

Gardenchicken, thanks for sharing. Several weeks ago Dollar Tree had some Styrofoam Balls. The 4" size was wrapped individually for $1.00 each. I'd like to try several sizes and grow moss on some of them. Were yours heavy enough that the wind wouldn't blow them around?

That is a good score! Good price for styrofoam balls, I might have to have a look for some! My largest is only about 3-1/4" dia. (finished size) and if it was sitting on a flat surface like concrete it would blow around, but sitting in a flowerbed or grass, no, I don't think it would move. I suppose it depends on how thick of a layer of hypertufa you add to it.

You could always add some type of weight to the ball before you coat it to help it stay in place.

I would suggest you TRY adding a little fire clay to make your mix more "sticky". It couldn't hurt.
Robert

Coat the ball with regular white (PVA) glue, and coat with white silica sand (aka 'sharp sand'). Do half at a time. Dry well. Then coat with your concrete mix.

Sue

could you then make a mosaic on top of the hypertufa and grout it? like this: http://pinterest.com/pin/142707881913550734/

Here is a link that might be useful: bowling ball mosaic

Do we think the PVA glue plus sand coating is necessary to help with adhesion if making spheres using small 5cm plastic children's balls?