I am going to try to explain how I go about creating a prosthetic make-up with over lapping foam latex appliances.  I decided to do a make-up that shows a person with severe skull and jaw deformations.

The first step is to make a plaster cast of the persons face.  This picture shows a silicone mold that I will produce the plaster cast from. There is no reason to make a solid copy so I will make a shell that is about 1 inch thick.  Simply brush the plaster into the mold until you have it as thick as you need it.  The plaster will begin to set up within 10 minutes so you won't have to wait very long.  The cast will be ready to pull out of the mold in a couple of hours.  Here is the plaster cast fresh out of the mold.  Because I will want to remove the sculpted features from the plaster cast later, I will coat the face with a material called Alcote. It creates a thin film over the plaster surface that will dry and be invisible. It is an important step to "floating the clay" off of the plaster cast.  I'll explain more later.

Now that the plaster cast is ready, it's time to sculpt. I use Roma brand oil based clay to sculpt with. Here is a picture of the design after about an hour of work.  After a few more hours it looks like this. Here is a side view of the sculpture during the first few hours.  I can't remember how many hours I worked on this sculpture but it was probably around 20. Here is a shot of the nearly finished sculpture. Close up of the ear

Since the sculpture will be broken down into smaller pieces, I have to make "blanks" or positive molds of each section of the face that will be covered by the sculpture once it is broken down.  These blanks will be used in the foam latex process so I have to make them out of Ultracal-30, an industrial hydrocal.  In this picture you can see the blanks and also the sculpture, which has been cut into sections.  The forehead will be one piece, the nose and upper lip will be another and each side of the face will be separate pieces.  Now, you're probably wondering how I got the clay sculpture off of the original plaster cast without destroying it.  The technique is called "floating the clay".  Remember that I put a coating of Alcote onto the plaster cast.  Well, once you are finished with the sculpture you use a thin knife to cut through the clay so that it is divided into sections then you take the plaster cast with the sculpture on it and put it in a tub of water for 24 hours.  The water will soak into the plaster and dissolve the Alcote.  After 24 hours you will take the plaster cast out of the water and the clay sections that you cut can be lifted off will to problem at all.  It's kind of amazing if you ask me.. Here is a close up of the forehead section that has been positioned and attached to the forehead mold.

As I worked on this design, after I had already cut the sculpture into sections, I decided that I might want to do the make-up without the nose that I had designed so I redesigned the sculpture a little bit so that the upper lip would be part of the side of the face instead of included with the nose sculpture.  This way I can mold the nose separately and decide later whether or not I want to use it in the finished make-up.  I also made one other change in plans that didn't really affect the design but did affect the mold making process.  Sometimes when you do a multi-piece, over lapping appliance make-up you can simply cut your sculpture apart then when the sections are on their separate face section molds, you can feather out the edges so that when you make the foam latex pieces and apply them each piece will blend smoothly into the one that it over laps.  This works fine if the pieces are thin but if the pieces are to be kind of thick, as they are in my design, it will be very difficult to feather the edges down.  It would be too drastic a change to go from a thick sculpted area down to the level of the mold.  I don't know if that made sense but believe me, it's true.  Anyway, since I am going to over lap two thick pieces, I had to make a mold of the plaster face with a copy of the foam latex forehead attached to it. From that mold, I made a plaster cast of the face.  Now I have a copy of the plaster face with the forehead section of the make-up built right into it.  From that face, I made new blanks for each side of the face.  Now I can attach the sides of the face to each new mold and feather the edges right into the sides of the forehead piece since it is a part of the new plaster face that I made the new blanks from.  Here is a close-up of the right side of the face on it's positive.  Here is a close-up of the lip area of the sculpture.  After the sculptures are on their separate positive molds, I have to blend the edges down and do some final detailing.  Then I will make the negatives of the sculptures and get ready for the foam latex process.

The first step to making a negative of the separate sculpted sections is to apply a thickness of clay all the way around the sculpture.  This layer should cover the entire top surface of the positive and it should stop no more than a couple of millimeters from the sculpture.  Let me explain the reason for this:  Let's imagine that you did not apply this layer of clay to the surface of the positive and you made the negative. After the mold is made you will want to fill it with foam latex, close it, then put it in the oven to vulcanize.  When you try to close the mold, the excess foam will want to flow out of the mold.  Makes sense right.  The problem is that no matter how hard you press the mold closed, there will still be a thin layer of foam latex sandwiched between the two halves of the mold. This layer is called FLASHING.  In order for the mold to close completely, there would have to be no foam latex between the two halves expect in  the gap that represents where your sculpture was. The surface of the positive that you did not sculpt on needs to mate perfectly with the negative..... Back to the foam latex.  The greater the distance that the foam has to travel before it escapes past the edge of the mold, the thicker the layer of unwanted foam will be that will remain sandwiched between the two halves.  This means that the foam latex appliances that you are making will have edges thicker than they would be if the mold were to have been completely closed.  So how do we solve this problem?  We build a layer of clay all the way around the sculpture so that when we make the mold and remove the clay, the negative will only be in contact with the positive no more than a couple of millimeters past the edges of the sculpture.  Since the foam will only have to travel that short distance before reaching the air space created by building the layer of clay, it will be much easier to completely close the mold and thus create the tissue thin edges on your foam latex appliances.

You will want to apply a thin coat of release agent to any exposed surfaces of the positive mold so that the negative does not stick to it. Sometimes I use vaseline that has been thinned down with Naphtha (a paint solvent). This time I used a spray on release agent called Ease release 2300. Whatever you use, make sure you put it on very thin. So thin that it might look like none has been applied.  Some people don't use anything at all around the perimeter of the sculpture, relying upon the oils of the clay that have soaked into the positive to act as a release agent.  I've never been that bold.  Usually when the Ultracal negative sticks to a small area of the negative that hasn't been greased it will either come off anyway (if you're lucky) or the negative will break off in that area and stay stuck to the positive.  I've never had a mold refuse to open because of not enough release agent. but I have had pieces break off.  If that ever happens, you can re-attach the broken piece with epoxy but the mold will never be as good.  Take your time and make sure you don't miss any areas.

The next step is to build a wall around the top of the positive that represents the boundaries and height of the negative that you will make.  I usually use water clay for this but this time I used oil based clay.  It really doesn't matter but water clay is cheaper and easier to work with. Plus, the clay will probably become contaminated with bits of plaster once you are finished making your mold and you may just want to throw the clay away.  So why did I use oil based clay for this? Well, I didn't have any water clay on hand..  I should mention that most of the time I make "cylinder molds".  These are molds that are made by creating a containment wall out of rubber floor mat then pouring the Ultracal into it.  I will talk about this type of mold at a later date.

Side note: Experienced mold makers will look at the pictures of my positive molds and wonder why there are no keys drilled into the surface for lining up with the negative.  My reason is simply that I don't feel keys are always needed if there are enough contours in the surface of the positive.  Those contours will become keys that will cause the negative to seat itself in the proper position.  The only time I would say that keys are absolutely needed is if the surface of the positive is completely smooth and flat, like a table top.  It doesn't hurt to have keys when they are not really needed but I try to cut down on unnecessary things. You will notice one spot on each of the two molds shown above that expose the surface of the positive.  I do that to help insure that the mold does seat properly when you close the two halves. Those spots might be considered keys.

Before you want to think about mixing up the Ultracal-30 for your splash coat, you will want to prepare some burlap, or hemp fiber or other material used to re-enforce the Ultracal.  I like to use burlap just because that is how I was taught.  I cut the burlap into small squares but the size depends on the size of the mold. For larger molds, I would cut larger pieces.  The purpose for the burlap is to strengthen the Ultracal and make it less likely to crack during temperature changes such as putting the mold into a hot over or taken it out of a hot oven later.  If you don't re-enforce the Ultracal, it will crack with the sudden temperature changes just like an ice cube in a cup of warm water.  If you ever take a mold out of a hot oven an hear little "ting" sounds, that means that the mold has cracked.  Most of the time those little cracks will not show up right away but each one weakens the mold and will eventually show up on the surface of the negative, destroying all of your hard sculpting work.  If you are using burlap or hemp fiber, you will want to soak it in water so that it is not dry when you use it with the wet Ultracal.  You want to make it damp but not really wet.  The reason that you don't want to use it dry is because when it comes in contact with the wet Ultracal-30 it will absorb the water out of it, thus weakening it.  Remember, damp burlap is good but wet burlap is not. If the burlap is too wet, the excess water will get squeezed out by the weight of the wet Ultracal.  This extra water will not just mix into the Ultracal.  It will try to find it's way out of the Ultracal and cause puddles on the top surface of the fresh negative or possibly form worm holes in the mold.  I hate it when it does that.

The first layer of Ultracal that you apply is called the SPLASH COAT.  As the name suggests you will be splashing the Ultracal onto the sculpture and surrounding areas of the positive. I've never had consistent result by just splashing on the first coat so I use an airbrush to blast the Ultracal over the surface of the clay and flashing area.  First I apply some Ultracal with a brush then I spread it around with the air pressure from the airbrush. Once the entire surface is covered with a good, bubble free coat, I apply some more Ultracal until I get a thickness of about 1/4 inch. After that.  I let the splash coat set until it begins to harden......   The splash coat is really the key to making a good negative. This layer needs to cover the sculpture and flashing without trapping air on the surface of the positive.  This layer also has to be strong.  The thing about Ultracal-30, or any gypsum product is that it's strength depends upon how you mix it.  If you mix it with a lot of water you will get really runny cement that will be weak when it hardens.  If you mix it with just enough water to make a thick paste, it will be very very strong but it will be impossible to apply it to the negative without trapping air.  I like to make my splash coat as thick as I can possibly make it while still making it thin enough to flow over the surface of the sculpture and flashing.  There is no way I can explain all that I have learned about Ultracal and other gypsum/plaster products.  It's really something that only comes with experience.  You have to get to know the material.

It is important, in my opinion, to let the splash coat begin to harden before moving to the next step but you don't want it to completely harden.  Some mold makers believe that if you let the splash coat completely harden then you can follow some simple steps to finish the mold and still end up with a very strong mold.  My tests show that a mold that has been completed after the flash coat has completely hardened is not as strong as a mold that has been completed while the splash coat is still kind of soft and wet.  It all has to do with the bond between one layer of Ultracal and the next.  If you allow multiple layers to harden at the same time then they will harden as one.  If you let one layer harden on top of a layer that is already hard, they will still bond together but not as strongly as they would have if they hardened together.  Please understand that this statement does not apply to all types of plaster materials.  For instance, if you were making a plaster mold you would want the splash coat to completely harden before moving on (see tutorial on mask making).

Once the splash coat begins to set up or harden you can begin applying burlap.  The Ultracal mix that I use with the burlap is much thicker than the splash coat.  It makes for a harder mold.  Before applying the burlap, I like to apply a layer of fresh Ultracal on top of the splash coat just so the first layer of burlap doesn't trap any air against the splash coat.  To apply the burlap, simply dip it into the Ultracal then apply it.  I usually apply as many layers as it takes to make the mold as thick as I want it to be. In other words, the the Ultracal soaked burlap will make up the rest of mold's thickness.  As you apply the burlap, press it down gently to work out any air bubbles.  After I have applied enough burlap, I like to apply a finishing layer of ultracal on top of it.  It makes the mold look nicer when you don't see burlap texture on the top of the mold but you don't really have to do it.  I smooth the finishing layer out with a steel then I let the mold harden for several hours or until the Ultracal completes it's exothermic reaction..  What??  Well, the Ultracal will begin to heat up as it hardens.  If the mold is big enough you will actually see steam rising from it.  This release of heat is called an exothermic reaction. Anyway, the mold will get very warm, sometimes hot.  Wait for it to cool down before opening it.  I like to open my molds when they are still a little bit warm because the clay comes out easier if the molds are warm.

You can usually open a prosthetic mold by pulling the two halves apart with your hands.  Depending on how you designed your molds and their size, you may have to pry them open.  These molds popped open with no problem.  I remove the clay by peeling it out.  If some of it doesn't want to come out, I use a small wooden tool to try to get under it.  You don't want to scratch the molds!  Digging the clay out of the negative of the ear takes a little patience but it really isn't a problem.  After I remove all of the clay I clean the molds with Isopropyl alcohol and a scotchbright pad.  The pad will not scratch the surface of the molds. Here are the molds before cleaning.  Later I will take them and grind off the rough edges.

After the molds are cleaned up, I put them together and bake them in the oven at around 190 degrees F for 6 or  7 hours to dry them out. It is very important that the molds are dry before you run foam latex. There are two types of water in an ultracal mold.. Well actually in any plaster or hydrocal mold. There is the water that is needed by the material as part of them chemical make up that keeps the mold from falling apart and there is "free" water. That is water that is in the mold but is not needed. Think of a mold as a sponge. The sponge can hold a lot of water but it doesn't need it. It just holds it because,,, that's what sponges do. They are hydroscopic in nature. That is to say, they like to absorb moisture. Molds are the same way. They absorb water and hold water but they don't need it for anything. Getting back to the sponge story, just like a sponge, Ultracal-30 needs some moisture to keep it from falling apart. Water molecules are important to cement and plaster products like Ultracal-30, just as they are important to the sponge. Anyway, the free water causes problems for the foam latex when the foam is vulcanizing or curing in a hot oven. The free water will turn to steam and expand, trying to leave the mold. In the process, it will push on the surface of the foam latex, causing it to lose contact with the surface of the mold. If this happens, the piece will have strange impressions in the surface of the foam. You will still see the detail from the mold in the foam but the piece will not be usable. I don't have a picture to show you since I try very hard to never let this happen. So, like I said, bake your new molds to get the free water out of them.

Time to run some foam! The key to having a good experience with foam latex is preparation. You need to have a good gram scale, an electric mixer, an injection gun (optional but recommended), a note pad, an oven thermometer and a stop watch. Of course, you will also need a foam latex system to use. I am using GM foam latex. It is a 4 part system that requires you to measure the components to exact proportions then mix them and whip them up. It can be tricky sometimes. the room temperature and humidity have a direct effect on the gel time of the foam. So does the length of time you spend mixing the foam. What is gel time? That is the time between when the foam is wet and foamy like shaving cream to the time it is soft and squishy like a marshmallow. You need to mix the foam so that you have enough time to get it into the molds before it gels. As stated, this has a lot to do with the temperature in the room (the hotter it is the faster the foam will gel), humidity and the amount of gel agent that you put into the mix. I could write a hundred pages on how foam latex gels or doesn't get but its one of those things that must be experienced. Getting the foam to get correctly is considered one of the hardest parts of making foam latex. That's why it is important to keep a record of your foam processing. This record will serve as a record of your victories and failures with the foam. It helps you to not repeat the same mistake twice. When you run a good and successful batch of foam, you can follow the same instructions for that batch to help assure that the next batch will also be a success (assuming that all conditions are the same).

Before you start making the foam, you want to apply a release agent to your molds so the foam will not stick to it. Zinc Stearate is the most common release used. When you buy a foam latex kit, it will include a jar of release agent. Brush it on to both the negative and positive. Let it dry for 15 minutes or so then brush off the exess with a clean dry brush.

You will need to measure the ingredients of the foam components carefully into a bowl that you will be using to whip it up. You won't be able to do this without a good gram scale. They cost around $120 to $150. The foam will have to be whipped up at different speeds on the mixer for specific amounts of time. The instructions that come with any foam system will give you a mixing schedule to follow. It will suggest the speed and amount of time that you need to mix the stuff. Of course, your mixer may be different than the one they wrote the instructions for so you may have to modify the settings. Here is the schedule that I used at 72 degrees F and about 50% humidity:

speed 1 for one minute (to mix the components together)
speed 7 for 6 minutes (to whip the latex into foam)
speed 4 for 3 minutes (to refine the foam)
speed 1 for 3 minutes (to further refine the foam
speed 1 for 30 seconds (to mix in the gel agent)
speed 1 for 30 seconds (back bowl the foam to further mix in the gel agent)

Back bowling is when you use your hand to force the mixing bowl to spin in the opposite direction. Its important that the bowl is always turning when the foam is being mixed. It helps assure that the material will be thoroughly mixed.

After the foam is mixed and the gel agent has been added, I poured the foam into the injection gun and proceeded to fill the molds. It's a good idea to use an injection gun even if you're filling open molds. It gives you control over the way the foam contacts the surface of the mold. You see, the foam is very thick and will now flow very well over the surface of the mold. If you were to simply spoon the foam into the mold, you risk trapping air between the mold and the foam. By using the gun, the foam can be made to move across the surface of the mold thus reducing the possibility of trapping air. Once the foam is in the mold, the mold has to be closed and pressed tightly shut. It is important to press the mold shut so that the exess foam will displace. Remember what I wrote about how the flashing needs to be thin if you want thin edges on the foam piece. Even a well made mold will not give you thin edges if you don't completely close the mold.

I vulcanize or cure or cook the foam for 3 hours at 165 degrees F then I turn the oven off and let the molds sit for an hour or two more. Even though the oven is off, the foam will keep on curing since the molds will remain hot for a few hours. Basically, after the molds have cooled, I open them and remove the pieces. The length of time that you need to cook the foam will depend upon the thickness of the foam piece, the thickness and type of material your molds are made out of and also the temperature that you cook the foam at. There is a lot of discussion about temperature and mold thickness but I'll leave that for another time.

Here is a shot of the foam latex from the nose mold. You can see how thin the flashing is around the nose. Once trimmed, this will be a very nice piece. Besides having nice thin edges, you have to inspect the cell structure of the foam to see if there are any large air bubbles in the foam that might make the piece unusable. To do this, I hold the foam latex appliance up to the light and look through it. If there are any large bubbles, they will be visible. If the bubbles are in a thick area of the appliance, you may still be able to use it but if they are in a shallow or thin area then you might have to consider the piece to be a reject and make another one. If this happens, don't feel bad. Just try to fugure out what went wrong and try again. Out of every 10 foam latex pieces I make, I get at least one reject. I use those to practice painting on. By the way, there are ways to fill in bubbles in the foam but I'll save that topic for another time.

You can wash the new foam latex pieces in water with a little mild soap if you want to. This will remove release agent and any byproducts of the vulcanization. I don't usually wash my foam but I do like to power new pieces with talcum powder. If the molds were made correctly and all went well with the foam, you will have some good quality foam latex prosthetics with tissue thin edges. Here are a few shots of the foam pieces. you can see how thin the edges are.

I hope this information is helpful to those who want to try their hand at foam latex prosthetics. A lot of things have to go right to make good quality prosthetics. If you're a beginner, plan on making some mistakes but don't give up. When you get it right, the results are well worth the effort.

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