Mask Materials Guide
Mask Making Material Guide Part One:
Hey folks. For all you lurkers that have ever wanted to try your hand at Latex Mask Making but didn’t know where to start, I have put together an intensive Mask Making Guide in question and answer format. This Guide will cover the materials and techniques that are commonly used in both latex masks and prop making.
For those of you seasoned veterans out there, there may also be some good info here which you can add to your knowledge base. Feel free to e-mail me if I missed something or made any omissions or errors. Contributions are welcome!
Why is a head armature often used when creating latex masks?
A human head form, also known as a head armature is used as a base upon which to create your character in clay. If your armature is a lifecast or premade headform created from a lifecast, you know that the mask will fit an average size human when it is complete (unless of course you use the lifecast of a child, women (smaller head on average) or a person with a smaller than average head or short neck) The best armatures are those made from a person with a long neck, like Doug Jones or an artificially elongated neck. This is because latex masks shrink as they dry. A longer neck on your head form will help offset the shrinkage factor. An added benefit to using an armature is that helps the eye holes of the mask line up better too. In addition to lifecasts, a wigblock, mannequin head or other kinds premade headforms can also work well.
Why does mask latex shrink?
The reason is simple: liquid latex is not 100% solids. Mask compounds average about 58-62% solids including filler, vulcanizers and non latex components of the recipe. As the latex cures to a flexible solid, some of the liquid components draw into the mold and to a much lesser extent into the air. The loss of some of these liquid components in the rubber is what causes the latex to shrink. Generally speaking the more filler that is added to the rubber mixture the stiffer the latex will become and the less it will shrink or feel like rubber. The lower the amount of filler added, the stretchier the rubber will be, but the higher the shrinkage.
Shrinkage and feel can also depend on the “cure package” that is used in the rubber. The type and quantity of accelerators and curatives that are added to the mix is an important factor in shrinkage. Mask latex can shrink anywhere from 5% to 15% depending on the brand used. An average shrinkage factor is 8%. High quality mask latex like the ever popular RD-407, contains a good balance of rubber to filler and a properly balanced cure system. Quality mask compounds made today will also typically use evaporated latex (a type of uncompounded natural latex) as their rubber base component, since the rubbers solids are higher with evaporated rubber. Prior to evaporated rubber the best rubber to use for mask compounds was cream rubber. Cream rubber is another type of natural rubber that comes directly from rubber trees but is no longer widely available due to the high cost of production. Both cream rubber and evaporated rubber have high rubber solids (68% to 70%) which add life and bounce to the latex Low mold adhesion is another benefit of high rubber solids. Masks that pull easily away from molds are most likely formulated with high rubber solids. Poor quality latex with low rubber solids will not have a snap to the rubber and will feel lifeless and dry with a slower return once cured. Too much filler and your mask will have a tendency to crack as well. Excess curatives in the rubber can contribute to this problem as well. Too much curative will cause the mask to continue to cure even after it appears to be fully dried. Masks that come from Asia will often use cheaper rubber and or an inferior recipe that is not meant to last. Believe it or not the best latex compounds in the world are formulated right here in the good old USA! Even the best masks coming out of Mexico over last ten years or so use American made latex compounds.
What is cold cure latex?
Mask Latex compounds can also be of two varieties. The first and most popular type uses what is known as pre-vulcanized rubber. Also known as prevulc in the industry, this type of mask latex uses a natural rubber base that is combined with curatives and heated for a specific number of hours to cause the rubber to partially crosslink or cure. As weird as it sounds, this puts the rubber into a partial state of cure even though it remains in liquid form. From that point, all that is really needed to turn it from a liquid state into a stretchy solid state is exposure to air. For masks though, there is still a bit more that needs to be added to the prevulc such as fillers and thickeners that will impart the remaining charactersitics needed for the recipe. The best latex compounders will often prevulcanize the latex themselves to further customize the blend and impart it with superior qualities. One main advantage of prevulc mask latex is that it has a long shelf life in its liquid state. RD-407 is an example of high quality mask latex that is pre-vulcanized.
Next time we will cover Ultra Cal vs. White Hydrocal for mask molds and different painting options for masks. See you next time for the Mask Making Material Guide Part Two!