Concrete molds can be made to build almost anything out of concrete, from gargoyles and lawn ornaments to simple concrete benches, counter tops and floor tiles. The mold only needs to withstand the pressure of the concrete and it has to be shaped to contain the form you want. For instance, a tile mold can be a simple, flat enclosed box made of plywood and held together with screws. There's a few more tips and things you should know as well. Does this Spark an idea?
Mold Materials
Concrete mold materials should be chosen for the end product. A tile or counter top mold should be made from sturdy flat melamine or plywood that is reinforced with struts. The main thing to keep in mind is support. The material has to withstand the weight of concrete. A melamine board that is 3/4 inches thick is strong enough to support 3 inches of concrete. More complex shapes should use forms that are made of clay or plastic. Always reinforce the form materials if you have doubts about their ability to hold the concrete.
Mold Building Tips
Concrete is not a completely solid material. It has pores and can easily crack after it has dried. For this reason, your mold must be completely water tight. If the mold dries unevenly because water is seeping out of one end the concrete is much more likely to crack and split. When you build a mold, always use silicone rubber caulking to seal the edges, especially between the edges of melamine boards. Apply the caulking to edges before you screw them together and then along the corners after your screw the boards together.
Making the Forms Release
Another problem people encounter when building concrete forms is the release. This is the stage when the mold form is removed. In some cases, the concrete can dry or stick to the form. Avoid this by coating the inside of the mold with release powder or compound. Use a generous application and make sure it is designed specifically for your type of concrete.
Rebar and Reinforcing the Molds
Reinforcing the molds is a wise idea. Professionals use rebar, which is long iron reinforcing bars that is strung between two concrete forms. This isn't a possibility with very small concrete forms. Instead you can insert metal mesh into the mold and pour the concrete over it. This metal mesh will hold the concrete together and reduce cracking.
Tags: concrete forms, hold concrete, metal mesh
