Mask Materials Guide

Hey folks. For all you lurkers out there that have ever wanted to try your hand at Latex Mask Making but didn’t know where to start, we 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 us if I we missed something or made any omissions or errors. Contributions are welcome!

Let’s begin…

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 it 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 softer 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 rubber's 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 some of 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 characteristics 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.

The other type of mask latex that is less common, but is sometimes seen with Asian Mask companies is called cold cure mask latex. With this type of compound, all the curatives and additives are mixed in at the same time to the raw latex with no heat added during the process. Cold cure mask compounds usually require a post cure in a heated oven once the dried latex cast is pulled from the mold. Post curing is necessary to finalize the cure (crosslink or vulcanize of the rubber particles) so the rubber will have a memory and keep its shape once dry. Cold cure rubber can eventually vulcanize on its own with without a post cure, but it takes a long while to do so. Besides the necessity for post cure, the main downside with cold cure rubber is that it has a short shelf life in its liquid state.

Ultra Cal 30 vs. White Hydrocal

Latex mask making uses a slip casting process very similar to the one used for ceramics. For those new to this medium, the basic concept is that when liquid latex is poured into the mold, an even layer of gelled rubber begins to build on the mold interior. The porous nature of the mold has a capillary effect on the rubber which first causes it to build up in the mold. The thickness of the rubber build-up is defendant on how long the liquid rubber is left in the mold. Then, once the excess latex is poured out of the mold, this same capillary effect of the mold combined with air exposure will cause the latex to dry for removal.

Ultra Cal 30 – Ultra Cal is a high strength, very low expanding stone or gypsum product that works similarly to plasters. Similar in the sense that once mixed with water, it will begin to react and after about 30 minutes, it will harden like plaster. That is where the similarity ends though. Unlike plasters, ultra cal will set to a very hard stone. Special effects artists have traditionally liked to use ultra cal 30 especially for foam latex molds because it’s high tooling accuracy. The benefit for using it in slip cast molds for masks is that it has a long service life. Ultra Cal will hold pattern detail much longer than white hydrocal.

Another benefit of that Ultra Cal 30 for mask molds is that it can be built up in layers without forming stress cracks.. This is again due to its strength and low expansion abilities. For this reason Ultra Cal 30 is the perfect material to use for making one piece, full head production molds for masks. The downside of Ultra Cal 30 for mask molds is that molds take at least twice as long to produce. It also takes quite a bit of practice to learn how to produce UC30 molds that will absorb the deposited latex evenly. Ultra Cal 30 molds that are not carefully made will have surface spots known as resistance areas where latex will not build up at all.

White Hydrocal

Many mask makers like to use white hydrocal for the majority WH is the primary choice for mass production. The main of their molds and advantage is that overall mold and mask production is significantly faster than UC30. Once WH is mixed with water, molds will set within 10-15 minutes on average depending on how thick it is mixed as opposed to 25 to 35 minutes or more for Ultra Cal 30 molds. The big downside with WH is that it has to be used in mass. In other words you mix up what you need in one shot and build it up over your sculpture until it completely sets. You cannot build up the mold in multiple layers and batches of gypsum like you can with UC30. WH molds made like this end up with stress fractures throughout the mold. These will show up as significant defects right from the get go when you go to cast your masks.

The second major drawback in molding with WH is that is has a very short service life. This is especially true if your mold has lots of detail. Each time you pull a latex piece from your mold, a small amount of surface detail is removed with the mask, and tiny air holes will begin to open up. When defects occur on the mold those are also defects that will show up on your mask. With each cast the defects gets progressively worse.

The same erosion effect happens with UC30, but it happens at a much slower rate. Given these problems, you may be wondering why anyone would choose WH for a mask mold. There are two main reasons: First, if only a few casts of the mask are required. And second, as silly as it sounds, some mask designs actually lend themselves to an eroding mold. So what kinds of designs are perfect for WH? How about Zombies, Corpses, and anything where defects will not detract from the mask. They might even help! In fact, most large mask companies will use WH and will simply make a large number of molds and use them for production until the quality of castings is no longer acceptable. When the mold reaches that point, the manufacturer will use a stored, thick latex copy of the mask (known as a production model), to make as many new molds as they need. Half masks are especially suited for WH since they only require a one piece mold and they can be easily replaced.

To sum it up, if you only need to make a few copies of your mask or if your design lends itself to mold erosion, than White Hydrocal is a good choice. If however, you have a highly detailed mask that you plan on making a couple dozen copies or more, than the clear choice is Ultra Cal 30. The extra time and effort you put into the mold will be worth it in the long run.

Rubber Cement Paint

When I first started making latex masks back in 1986, there was very little info on how to paint a mask. At the time, the conventional wisdom was that rubber cement was the best option. Published in the early 1980’s, Tom Savini had some info on this method in his excellent book, Bizarro, but that was about all I could find at the time. Any of you who have the book may recall that Tom’s recipe was acrylic paint mixed with rubber cement and thinned with Rubber cement thinner. When it came time to paint my first mask, I couldn’t wait to try it! Unfortunately, I quickly discovered, acrylic paint is water based and rubber cement is a chemical solvent based product. So no matter how hard I tried or how many mixtures I made of this recipe, I could not get it to work! I was so bummed out. As it turned out, the book had a typo and the proper pigment was not acrylic paint but rather oil paint. For me, the great lesson there was if you read it in a book, it might still be incorrect. Typos do happen. Fortunately, my persistence and frustration eventually led me to try the oil paint, which made much more sense. And of course it worked! Once I got it going all I needed to do was experiment. I also discovered that rubber cement is toxic!

What is rubber cement paint and how is it made?

Rubber cement paint (RCP) is a simple mixture of 1 part oil paint to about 5 parts good old off the shelf rubber cement. This mixture is typically thinned down with mineral spirits or VM&P Naptha to a pourable consistency. The result is a paint that sticks like glue to rubber and flexes with the mask without cracking or rubbing off. The real benefit is that rubber cement actually bites into the mask and gets into the pores of the latex. The solvent causes the Mask Making rubber to swell slightly which opens up the rubber pores and allows the rubber to get in. Once the solvent flashes off, only the rubber cement remains, which is now tightly locked onto and impregnated into the latex rubber. This is the reason why the bond is so strong. With that said, you may be wondering why everyone isn’t using rubber cement to paint their masks. The answer is simple. This stuff is TOXIC!!! And unless you work area is unbelievably well ventilated, you use chemical resistant gloves, and you have an enclosed air supplied ventilation suit, I do not recommend using this as a general purpose paint medium for your masks despite its effectiveness.

When is it appropriate to use rubber cement to paint a mask?

Rubber cement can be made somewhat less toxic by replacing the thinning solvent with D-Limonene, a natural, citrus solvent made from oranges. One of my favorite uses of rubber cement paint made with D-Limonene is for creating a rubout effect on a mask. The way it works is that you start out by putting down a base coat layer of latex mask paint (more on that later). Once the Mask Paint is dry, a very diluted mixture of rubber cement paint that is significantly darker than the base color is applied with a sponge. Once the RCP is dry you carefully go back over the mask with additional D-Limonene applied with a rag. The rag is first soaked in D-Limonene which is than used to gently rub the high points of the mask until most of the RCP is removed from those areas. The result is a high contrast accentuation of all the shaded areas of the mask where the darker colored rubber cement remains. Done well, the rubout can bring out all of the fine details that you can put into a mask design and serve as a beautiful background for additional detailing and color layering.

Keep in mind that even with using D-Limonene as a solvent replacement, you still need to take careful precautions to protect yourself from the solvent that is in the cement itself. Incidentally, rubber cement paint made with D-Limonene has a slower evaporation rate than mineral spirits or other chemical solvents. It is also worth noting that Rubout or rubber cement paint can be layered in with latex based paints such as mask paint and are therefore completely compatible.

What are some of the safer alternatives for painting Masks?

Good question. Fortunately there are a number of safer alternatives to painting masks that are just as effective. The next oldest method that a number of mask makers like to use is PAX Paint. For those of you unfamiliar with Dick Smith’s PAX formula, this is a mixture of Prosthetic Adhesive (Prosaide or similar) that is mixed with Liqutex acrylic and thinned with water. Liquitex Acrylic Paint comes in a wide variety of color choices that can be intermixed for an almost unlimited palette of color. Another nice thing about using PAX to paint latex is that it is non-toxic and can be made to go on like water colors. Colors can also be made translucent and built up to create depth and fine detailing on the mask. Some artists have added a much as twenty parts water to Prosthetic adhesive without losing the adhesiveness of the paint. This is good because Prosthetic Adhesives can be very expensive.

Another drawback of using PAX paint for masks is that it tends to remain quite tacky after the paint dries. The traditional method of removing tack is by powdering with talc. To get around this for masks we simply make a more dilute blend of paint with a higher concentration of water. This reduces the tack enough that it does not present a problem. To eliminate the tack completely a mask painted with PAX would need to be sealed with Krylon Crystal Clear. The major downside of PAX paint for masks is that it does not bite into the mask and is not as flexible as some other paint options. PAX paint does tend to crack if the mask is flexed and can rub off if handled excessively. For that reason, PAX would only be recommended for display masks only.
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