Casting and Creating Modeling Work With EnvironMolds, LLC

Liquid latex rubber is a popular art material that is used for making latex mask as well as creating other theatrical effects such as wrinkles, scars and gashes for film, television and stage. The cheap price coupled it qualities of toughness and durability make latex rubber a commonly used material in the world of art.

However, regular latex rubber proves to be quite viscous. Fillers or extenders are required to control the flexibility or rigidity in the rubber latex castings.

EnvironMolds offers ‘RubRfil Latex Mold Rubber Filler and Extender’ expressly for this purpose. All you have to do is mix requisite quantity of RubRfil with the liquid latex rubber. This will thicken the mix and also extend the material so that you need to use less quantity of latex rubber.

RubRfill works by subtly altering the form and function of the latex. Varying the amount of this extender and hardener enables you to easily control the amount of hardness and flexibility as desired.

For beginners, the following recommended combinations will prove handy:

•    Very flexible - 1 part liquid latex rubber  to 0.5 part RubRfil

•    Flexible - 1 part liquid latex rubber  to 1 part RubRfil

•    Medium flexible - 1 part liquid latex rubber  to 1.5 parts RubRfil

•    Very hard - 1 part liquid latex rubber  to 2.5 parts RubRfil

You can work your way through these suggested ratios to get the kind of flexibility or hardness you require.

Enlarging a mold or cast is an easy and enjoyable process. Specially formulated polyurethanes and other compounds are available that allow for scaled expansion of a model.

However, shrinking a cast is a different ballgame altogether. You may consider using materials like alginate, wax or latex rubber that shrink during curing. However, the shrinkage is not proportionate and you will only end up with a deformed version of the original.

What you desire is uniform and balanced reduction with the details staying proportionate to the reduced size!

This is still possible by using special solvents. For this purpose, the original mold should be resistant to solvents or coated with a solvent resistant spray to protect it from the harsh effects of the excess solvent. Blend the silicone rubber with the solvent to get a thin mix. This will be flowy and take considerable time to cure. Once semi-done, demold quickly and leave it to dry.

The solvent evaporates to gradually shrink the cast in a proportionate manner all over. While the level of shrinkage depends on the amount of solvent added, it generally takes 3 days for the cast to reduce to 85% of the original. Leaving it for 7 days will further shrink the size to about 80%. You can make successive casts to get further shrinkage.

Some artists substitute the solvent with odorless mineral spirits that again tend to evaporate, leading to proportionate shrinkage.

Similarly, some water based urethanes are also available that successfully reduce the size of a cast to scale.