Foam Latex

 

 

As a material for making prosthetic appliances for special makeup effects, foam latex is, in my opinion, unrivaled for performer comfort. It is incredibly light, strong and durable. Silicone does not breathe, and an active actor wearing silicone appliances will begin to perspire rather profusely beneath the silicone if it is worn for an extended period of time. Gelatin can actually start to melt after being worn for a long time. Appliance materials must be chosen based on numerous factors such as climate, shot framing, performance, and budget. When foam latex is made well, it feels like velvet, and every subtle expression and nuance of emotion is translated beautifully through the foam from the performer; it becomes the performer. A nearly full face appliance will likely weigh less than an ounce and, when applied, is almost undetectable by the actor wearing it. Its ideal for bid suits and fantasy creatures.

 

Moulds: Foam can be run in a variety of moulds, including gypsum, fiberglass, plaster, and epoxy. Ultrcal is porous, so it needs to be properly sealed and released to prevent the foam latex from adhering to the mould. Every bit as important as sealing and releasing the mould is making certain there is no moisture left in the mould before baking foam latex in it. 

 

Drawbacks: However, although foam latex is extremely light, strong, breathable, and expressive, there are some qualities that could be construed as negatives by some. First, foam latex is opaque. To create the semblance of translucency, the appliance must be painted with numerous transparent layers of pigment, usually with an airbrush, to achieve the look of real skin. Second, foam latex requires a heat cure in an oven, and it cannot be the same one used to cook food. Why? Because third, foam latex gives off toxic fumes during the heat cure that will render your oven forever unfit for cooking. One alternative is building your own makeshift oven using infrared heat lamps in a well insulated plywood box. Foam latex should cure in an oven that cannot exceed a controllable 200'F. Ideally foam should cure no hotter than 185'F (85 degrees). Lower temps (150'F-ish) for an even longer time will result in softer foam. It should be left in the oven for about 5 hours. Foam latex shrinks. The thicker the foam, the more it shrinks. That's not to be confused with the volume of the foam; lower-volume foam (heavier) will shrink more than high-volume foam (lighter) because it has more air and a lesser proportion of foam latex componants. It is water loss that causes shrinkage in the foam. Because higher-volume foam stretches more than denser, lower-volume foam, any shrinkage that does occur can usually be compensated by stretching, with a little force exerted on the foam. What the mould is made of also contributes to the shrinkage of the foam or the lack thereof. A porous mould, like Ultracal will cause the foam to shrink less because it absorbs moisture from the foam. Latex goes off after about 6 months. 

 

Colouring: Skin Illustrator, powder, acrylic paints and special pigments can all be used to colout foam latex. Pax paint is usually used to paint it. Tha flange can be trimmed with scissors.

 

 

Method

 

It can be helpful to work with a sheet with times and measurements on to help keep track of everything, as it can get confusing

 

Before you start mixing the foam latex, its important to ready the mould. For our small, plaster moulds, we marked match-up lines on them with sharpies, so that they could be accurately aligned for accuracey. The mould release is obviously dependant on the mould, but vaseline can never be used as it doesn't work with foam latex. For plaster moulds one layer of zinc sterait or solid soap works well. For silicone moulds and fibreglass, spray on one layer of display mount or spray glue.

 

A typical batch of foam latex consists of a cream latex base (this is different to normal liquid latex), which is specifically mixed with other products (ensure to shake it well before pouring). To this you add a foaming agent; 20% of the amount of latex you have and also 10% of the curing agent, which gives it the sponginess. Also weigh out 10%-14% of the gelling agent. This is added after the other products have been mixed and the amount depends on the temperature of the workplace and the weather; the colder it is the more gelling agent you will need. This helps the foam to set before you put it in the oven. The products are mixed in a mixer, such as a KitchenAid mixer used for cooking. The latex base, curing agent and foaming agent are mixed for about 6 minutes. The gelling agent can then be added and another 3 minutes of mixing ensues. 

 

When the batch is mixed, use a brush to start applying the latex into the mould. Fill it up with more than is needed so it can fill all the spaces and bleed out. Hitting the mould against the work surface can help any air bubbles to come to the surface. Then the two halves of the mould can be pressed together and left for about 10-30minutes to cure. Pressing the foam with your finger and seeing if it springs back, is enough to know whether its ready to be put in the oven or not. Non-porous moulds tend to take longer to cook. It works out about 1 hour per cm of plaster mould in the oven, and 1 hour per mm for a fibreglass mould. As our were only small moulds, they were only in the oven for a couple of ours. Turn the oven off and let the moulds cool a little before removal, otherwise they could break if they're suddenly brought to room temperature. Using a finger again, make sure the foam is fully cured by seeing if the foam springs back. Use lots of talc with a brush upon removal, as unpowdered latex, especially thin sections, will stick to itself and can totally distort a piece. 

 

When the piece has been removed, it must be washed before colouring and application due to the chemicals. It should be washed several times in warm water and fairy liquid. The chemicals should be squeezed out and gloves should be worn during this process. This should be done until the water runs clear, and then wash the piece a couple of times just in warm water. The piece should, if possible, be put back on the positive mould whilst drying. FOm latex can be applied with prosaid and although it cannot be blended, bondo can be used to smooth edges.

 

Alternatively: Rather than just pouring the latex into the mould, it can also be injected. It is injected through a hole in the positive mould and exits through bleeder holes in the negative mould. These are filled in with water-based clay during the process, as wax-based clay melts when put in the oven. 

 

Debrecini, T. (2012) Special Makeup effects for stage and screen: making and applying prosthetics. 2nd edition. United Kingdon: Taylor & Francis