G'day everyone, just thought I'd share an easy way to make realistic fake rock. This technique is just a modification of techniques used to make concrete rocks for landscape gardening. All I've done is take the final finish and apply it to a lightweight polystyrene base. The result is a tuff and very realistic lightweight rock that will easily handle dragons and small monitors. With a few more coats it would probably handle larger monitors too. The downside (like most realistic fake rock) is that it is not a sanitary surface. Like a real rock it is rough, slightly porous and hard to spot clean. I would try to make it so you can remove it occasionally and hose it down. Anyway this is what you need.
Polystyrene
Scavenge around to find polystyrene. Try tips and junk yards, I got more than I'll ever need from a junk pile at a milk factory. It was an old freezer lining but once I removed the tin, stripped the glue and soaked it in bleach overnight it came up as good as new.
Color Hardeners
Color hardeners are a mixture of off-white portland cement, mineral oxide pigments and fine sand (1:1:1). They are used to add color to various cement based products and dry almost as hard as concrete. They are sold in powder form and you can buy the oxide powders separately and make your own by mixing the above ratios. Art and hobby stores sell small amounts of mineral oxide powder and common colors can be found at most hardware stores. A 1kg tub of black, brown or red pigment costs less than $10 and a small bag of portland cement around $5.
Concrete Bonding/Sealing Agent
You need a concrete bonding/sealing agent (acrylic polymer) to bond the color hardeners to the polystyrene as well as each layer of hardeners to the next. This forms a plastic like bond giving flexibility that strengthens and holds everything together. There are many different brands available so look for a cement additive/surface bonder/sealer that dries clear and non-glossy. A similar product that you can readily find is Bondcrete and a 500ml bottle costs less than $10.
Note: This is essentially a concrete rock and these products will not harm your animals but if you want to use your rock as a water feature I would use a product like Pondtite between the base coats and final color.
The polystyrene before I ceaned it up and color hardeners. The dark black powder is straight mineral oxide pigment and the lighter black above has been mixed with sand and cement.
OK, lets start by making a rock formation. In theory you could use any material that's rigid enough to hold it's basic form but polystyrene is easy to shape. Just start breaking the polystyrene away at the edges and shaping it. I use a paint scrapper and a couple of screwdrivers. Don't get too fussy it will break away and look natural on it's own just use your thumbs to round off sharp edges and make the shapes you want. Use the KISS principal because you don't want areas that your animals or insects can get to but you can't. Also watch out for crevices you can't get to with a paintbrush (if you have to get complicated coat hard to reach areas before gluing your layers together). Making a built in wall is pretty easy, just start at the bottom and go for it. Making a 'free standing' rock is a little harder and it's easier to start at the top and work your way down.
The basic polystyrene structure. I use a latex based glue to hold everything together. It dries fast and seems to hold better than fast drying hard glues.
Now just coat a section of your formation in Bondall and Sprinkle color hardener over it (just use a common color for the base coats, I use grey). Now grab a paintbrush and tamp it down so the powder becomes damp and pasty. Continue sprinkling powder and Bondall as needed until you have an even first coat over your entire formation (you don't want to make it too thick, just cover the polystyrene). Leave it overnight to dry and repeat this step (use Bondall and let it dry between layers) until you have the thickness you need.
Here is my rock after two base coats of color hardener. It's now a hard solid structure that would break your knuckles if you punched it.
Now all you need to do is color, texture, highlight and age your rock. The colors you use are totally up to you this is just an example of how to go about coloring your rock. Sprinkle a few colors over your rock so you get good variation and tamp it down with a paintbrush dipped in Bondall so that the rock is mostly one color with some areas darker and some lighter (use a dryer brush to get less mixing of color). Now mix a little dry sand with black, red, brown or whatever colors your using and sprinkle it over the surface while it's still wet, this will bring out the texture. Now leave it to dry overnight then wash off the excess and loose sand. What you are left with is the overall color of your rock and it's almost finished.
To add highlights to your rock mix the color hardeners with water to a thick pastey consistency and with your hands just add highlights of color here and there. Now all we have to do is tone the color down and age the rock. Mix black oxide powder, with water until you have an almost transparent mix (this is known as a tint or dye). Now just flick the transparent mix over the rock work. The idea is to tone the color down and make it look natural.
Adding color highlights. You can't really see it in the pictures but highlights add that extra touch of realness.
The almost finished rock after being tinted with black oxide pigment.
Once the tint has completely dried give it a final coat with bondall to seal in the color and your rock is finished. If you made your tint to dark wash some of it out and let it dry before sealing it.
And thats all there is to it! You now have a very realistic hard wearing rock, that is much lighter than a polyurethane rock of the same size.
