Submitted by Bird Guy on 8/4/99. ( )

Would like to know how to mold an artificial rock. I need to make one asap for a customer and never really thought about this or bought any books on this before. Thanks

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This response submitted by frank on 8/4/99. ( )

Are you looking to cast or make one of mache? Either way you can take liquid latex and coat a rock to about 1/16" thick. This should take a couple of coats. Then the finally take some nylon ( the wife or girl friends old pair) cut into strips and mold them over the rock. After all is dried make a cut in the latex the bottom side and take the rock out. From there you can pour foam in to make the rock or thinned bondo. and coat the inside with it. Take out and paint it.
The other method is take a piece of old foam cut it in the shape of a rock or pour foam to make the rock size needed and after this is set, take paper mache ( for rocks) from any supplyer, and cover it. After it's set and dry usually the next day take some dry paint (tempra)and mix with water and cover the rock with this wet watered down paint to the desired color you need. Use blacks, browns,reds, purples, greens etc.

Casting stones

This response submitted by Leanna on 8/4/99. ( )

Can also use paper mache/plaster mix over a chunk of foam, and while still wet, spray on some paint and dab at it with a wet sponge and or squirt lacquer thinner on it, let it roll off and dab and spray some more, and you come up with some pretty fool proof rocks. Put some cracks in the wet mache with tongue depressor befor all this and the paint will stay darker in those areas and that looks pretty cool too. Rocks are fun to make, so hey, have fun! You almost can't mess up a rock!

Realistic rocks

This response submitted by Mike on 8/4/99. ( )

Molding latex works great for making cheap, reusable molds. Brushing on seven or more layers of latex (following the manufactures suggestions) without reinforcement has worked well for me for several years. I also have not used mother molds for these rocks. With this method, a rock slightly smaller than a soccer ball, and virtually any shape, can be molded.

Before spraying Synlube 531 release agent, I will invert the rock mold, inside-out, to better coat the surface being cast. Reinvert so casting surface is on the inside again.

Using WASCO's Liqua Cast mixed with dry tempera paints, sand,vermiculite, texturing "tools", etc., one can make very real looking rocks.

"Recipe" for making a light colored rock:

Using white tempera powder, mix in to either part A or part B of the Liqua-Cast, (If you would like some dark streaks in the rock, mix a similiar combination but a darker color). Mix some of the light A with some of B, at 50-50 ratio. Pour into the latex mold and swirl the Liqua Cast around, coating the inside of the mold. Before it sets, use a paper towel and dab, wipe etc., inside the mold, removing most of the casting material. Before what remains sets, pour in the sand, vermiculite or whatever, again coating the inside, then pour out the excess sand, etc. The sand will bond to the Liqua Cast and will show through on parts of the rock.

Mix the remaining light A and B parts and thoroughly coat the inside. As you are coating the inside of the mold with the lighter color, add a small amount of the darker premixed Liqua Cast. Several layers may be poured to thicken the "rock" walls.

When the casting material is set, pour in a urethane foam, small amounts at a time, coating the walls of the rock first. After the first coating pour of foam, add one or two more pours to fill the rock with expanded foam. If foam is added to quickly, the rock may crack. After the foam is no longer expanding, just a few minutes, remove the latex mold and you have a "real", complete rock.

What is neat about this method is no painting is involved. Colors tend to come from within the rock. And the combinations are unlimited. Even changing the shape of the rock is easy by just holding it and putting pressure on it to change the shape, as the first pours of foam are setting.

An alternative to the sand etc., is to flick or dab small amounts of black powdered tempera with and artist's brush inside the rock mold before adding any casting resin. This is added directly to the latex surface after sprayed with a release. This will add interesting patterns and spots on the surface.

The method described is a basic rock. Here is where one can get very creative. Personally, this is one of my favorite parts of creating habitat scenes. I will usually spend 45 minutes to one hour from start to finish on a single rock casting project.

If you should have any questions, or you would like to try this method but can't follow these directions, (I personally struggle to follow and understand directions), send an e-mail and I will be glad to help.


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