When it comes to a heads-up between polyurethane and silicone rubber for making molds, both have their own set of benefits going for them. Following is a look at certain factors that can influence the decision.

When it comes to making a mold, artists usually find themselves confused about whether they should choose polyurethane rubber or silicone rubber. Both are excellent materials that capture details well and deliver sound durability apart from resistance to the elements. Using a vacuum chamber will further enhance the efficiency of the mold by making it bubble-free.

Let us take a look at the properties of both materials before deciding which one is better.

The good thing about polyurethane rubber is that it delivers higher strength and comes in a wide range of hardnesses. The cost factor is also favorable with a low to moderate price. However, keep in mind that the rubber requires careful application of release agent to ensure proper demolding. It also proves to be moisture sensitive when in liquid form.

On the other hand, silicone rubber does not stick to anything except itself. Therefore, no release agent is needed as such. It provides excellent chemical resistance, but the comparatively higher cost can prove to be prohibitive.

Silicone rubber actually throws up two choices of tin-cured and platinum cured silicones. The latter does not shrink on curing and the cured mold has a lengthy storage life too. But bear in mind that the curing can be inhibited by certain surfaces.

Apart from this, the choice of mold making material will also depend on the following factors:

• What casting material am I going to use?

Polyurethane mold rubber is the material of choice for making molds for casting concrete, wax, plaster or even epoxy resins. The material can withstand the corrosive materials and return excellent results. However, when it comes to making polyurethane or polyester resin casts or even foam castings, you will do better to make the mold with silicone rubber.

• How many castings do I need to make?

Polyurethane mold rubber is suitable even when the casting artist intends to make scores of castings of concrete, wax, plaster or even epoxy resins. Similarly, when it comes to making multiple copies of polyurethane or polyester resin or even foam castings, silicone rubber will prove to be the perfect choice.

• What material is the model made of?

There is always a chance that the model can get damaged during the mold making process either because of the release agent or the oils from the mold making material seeping into the model. Therefore, it is always better to perform a small test cure on the model before making the entire mold. Using silicone rubber will eliminate the need for release agent, but they can still secrete oil that can affect the model.

EnvironMolds offers a range of mold making and casting materials along with vacuum pump with vacuum chamber to ensure bubble-free molds and casts.