Making Artificial Rocks
The addition of stonework to a vivarium or aquarium can dramatically increase its aesthetic beauty. Natural stones are quite heavy and it is difficult to customize their shape to fit your terrarium. Making fake rocks from styrofoam is not a difficult process. In fact, creating artificial rocks is an inexpensive and relaxing art project, with almost guaranteed success.
Here is an overview of the process:
1. Plan out the general shape that you want the rockscape to be.
The size of your rockscape will obviously be determined by the size of your vivarium. It is generally easier to construct the rocks outside of the terrarium, and then move them into the vivarium after construction is complete. If you will be making a background for the terrarium, make sure that you will be able to squeeze it in after constructino is complete. If your terrarium is front opening, it is possible to construct the rockwall directly in the tank.
2. Obtain some styrofoam and glue it together to make a solid mass.
The best material to use for creating artificial rocks is extruded polystyrene foam sheets (styrofoam), which is sold as insulation at Home Depot or Lowes. The 2 inch thick sheets work well. They might be blue or pink, but these will work fine. Alternatively, any lightweight foam can be used. Used foam that comes as packaging in a computer box is a free alternative, but it may be more difficult to sculpt. Styrofoam is easier to work with than polyurathane foam (Great Stuff) because it easier to cut, doesn't have large pores, and can be melted with a heat gun or a soldering iron. Once you have acquired the foam, you will need to glue it together to generate a mass which you can then carve away at. A hot glue gun works well for this.
3. Sculpt the foam into the desired shapes.
An Exacto knife is the most useful tool when sculpting styrofoam. When cutting off large chunks of styrofoam, you can use a flat knife or a serrated knife. A sharp flat knife is recommended, because a serrated knife will create a mess of styro-snow. To create a more natural look you can shape the mass with heat. A heat gun, blow torch and soldering iron all work well, but MAKE SURE TO USE THEM OUTDOORS IN A WELL VENTILATED AREA! This process will create toxic fumes. Sculp as much or as little detail as you like, but remember that this will ultimately be covered in grout, so you will lose the small details. Be liberal when creating nooks and crannies, you can always fill them in later, but a very three-dimensional rock will be more interesting. You might want to add some holes for plants to grow in, or to create a water pool.
4. Get some grout and acrylic polymer.
Grout is the stuff which you put between tiles. It is essentially Portland cement, and it is what you will use to create the surface of your rocks. Grout is available in a number of different colors, and if you buy multiple colors then you can mix them to create different shades. Since we are using the grout for a purpose other than what is was designed for, we will need to fortify it. Acrylic polymer needs be added to the grout in order to stabilize it. The acrylic polymer prevents the thin layers of grout from cracking and flaking off. Grout is available with multiple particle sizes, from very small particles up to sand sized particles. You might have better luck with the smaller particle size, but the larger particles will give a sandstone-like appearance. When you mix up the grout/acrylic polymer, make the grout more watery than suggested, which will allow you to paint on a thin layer. If you later need to fill or sculpt a larger area, make up the grout thicker.
5. Apply the first layer of grout with acrylic polymer.
You will want to apply lighter layers of grout first, and darker layers later. This will allow you to wear away at the rock and create a natural weathered look. After you have mixed up the pale grout and acrylic polymer, paint it onto the entire styrofoam surface. You might find that a thicker layer (2 millimeters) will adhere better to the styrofoam. Also, styrofoam with a rougher surface will adhere better to the grout. Acrylic polymer cures by drying, but grout must remain moist in order to cure. Between each layer, let it dry out. The acrylic polymer will stabalize and hold the layer together while you apply the next layer. While the first layer is drying, carve out some grooves and cracks, which will provide detail in the final rockscape. The grout will first dry on the most prominent surfaces, and last in the nooks and crannies. Take advantage of this to achieve a naturalistic result.
6. Add the next layer of grout.
Make the second layer of grout slightly darker than the previous, so that when you wear it away the lighter under-layer will be exposed. This layer should be very thin, just thick enough to cover the previous layer.
7. Repeat step 6
Build up multiple thin layers of grout as many times as it takes to get the desired shape. You can use a fan to speed up the rate of drying between layers, but heat might cause cracking.
8. Apply the final layer
Wait a day before applying the final layer, giving the layers thus far time to partially solidify. The final layer should be a very thin, dark layer. After you have applied the final layer, wash it away from the high points leaving it in the nooks and crannies. Now, to create a authentic worn look, use a wire brush to scrape away at the outer layers. Depending on how much the under-layers have solidified, you may need to use a lot of pressure, or just slight pressure. The most exposed surfaces should be worn down the most, allowing the brighter layers to show through.
9. Let the finished piece dry thoroughly.
This step is to ensure that the acrylic polymer has completely stabilized.
10. Moisten the whole piece for two to four weeks
This step is critical. Concrete will only cure when it is wet, and takes several weeks to fully cure. To keep it moist you can cover the whole thing in a trash bag, or submerge it underwater in a bucket or aquarium. If it is not submerged, mist it occasionally.
11. Neutralize the pH and rH
Freshly cured cement will dramatically raise the pH and rH to levels not suitable for plants and animals. Before adding your beautiful new faux rockscape to your vivarium or aquarium, you need to neutralize it. This is best done by soaking it in water and changing the water once a week for four weeks. If you are in a hurry, you can continue to change the water and periodically check the pH and rH. The piece should be cured when they no longer rise.
12. (Optional) Seal it in epoxy
Some people prefer to seal their artificial decor in epoxy. Feel free to do so when you are done, but I do not think it is necessary. The epoxy will create a shiny surface and will inhibit the growth of moss and algae. If you have a UV bulb on your tank, the epoxy will yellow over time.
13. Enjoy your new artificial rocks!
Place them in your terrarium. If they are to be submerged under water, you will need to glue them, since they float. Although your have by now created a wonderful stone facsimile, remember that it is not actually stone. Take care not to put too much weight on them, so that they do not crack. The instructions are for small animals, such as frogs. Larger lizards and turltes will required thicker layers of cement for extra support.
