Plaster Molds for Concrete

Unlike minerals that are easy to process with plaster molds, concrete is a bit hard, but can still be molded. This article contains stepwise instructions on how to create the perfect concrete plaster mold.

There are two important processes to do to ensure that you won’t end up with broken plaster molds for concrete. First is to create a “bed” made out of sand. This is done by packing wet sand inside a box. Wet the sand until it will hold its shape when you squeeze a handful. The wet sand would then support the plaster mold. Second is to put a generous amount of a very good release agent. The best release agents are those that are oil-based, like petroleum jelly. This is method is also even used in plaster molds for ceramics.

To understand the concept of making plaster molds for concrete better, let’s get to know the two elements: concrete and plaster.

Concrete is a widely used construction material all over the world. It is composed of cement and other cementitious materials, such as fly ash and slag cement. They are then mixed together so that they can be cured. During curing, a process called hydration happens. Hydration is when more of the cement reacts with residual water. This is when concrete becomes hard. This is also the process that can make plaster molds for concrete different.

Plaster, on the other hand, is referred to as gypsum powder, popularly known as plaster of Paris. It may be used to create complex detailing when constructing room interiors. Since plaster is easy to handle and process, it is easier to make details for it. As plaster hardens, it expands and slightly contracts before completely hardening. The plaster molds for concrete is used so that concrete can be formed into intricate designs.

Plaster cures by absorbing water in its vicinity. Cement cures by having the exact water that it needs so that it will have strength. This would then pose a problem since plaster absorbs water while cement needs all the water that it has. So, to have compatible plaster molds for concrete, get an effective epoxy paint and cover the inside of the mold with it. Use a spray-on type and paint the mold twice for a smooth finish.

You’ll still need a release agent so that it will be easier to separate the mold and the concrete. To ensure that the plaster won’t suck out the water from the concrete, soak the plaster well beforehand. Use just enough time and water so that the plaster won’t be affected.

Aside from epoxy paint, you can also use a good amount of petroleum jelly. This will stop the plaster from sucking water. Some would say that plaster molds for concrete can only be used once, but there are always means and ways.