Urethane mold tutorial

In this introduction to urethane moldmaking we will cover both a simple silicone master mold and making a urethane positive.
After this we will sculpt a new face and make a negative mold. After that we will create a face prosthetic in silicone.
Be ready for a ton of information which will be really boring unless you are a nerd like me!!
I wrote this article for The Makeup Artist Handbook by Gretchen Davis and Mindy Hall. Check it out! It's a great read!   http://www.amazon.com/gp/product/0240818946/ Did you get here directly and have no menu at the top? Go to the main web site!   Making a silicone master mold: To make my urethane molds I start by making a normal life cast in plaster using alginate or silicone.We will make a master mold out of it. Try to identify all possible undercuts that can be a problem in the mold making.  Typical examples of these are shown in the picture. There are several other undercuts that should not be removed. Like undercuts at the nostril or side of the nose. If these are removed your finished piece will not fit your actor as well as it should. All the chosen undercuts are removed by filling them with plasteline clay. Try to mimic the original texture of the face on these parts. All other defects on the plaster cast are also fixed up. For this demo I used a plaster cast that I fixed up but quite often these days I never make a plaster cast at all. I instead fill the face cast with molten clay as you can see in my fake head tutorial. Check it out! There are many ways to thicken your silicone depending on which brand you are using. I have found  Poly fiber to be great as a filler.  Poly fiber blends into most silicones with ease and will not cause too many bubbles. We will also use it later to thicken our urethane plastic. On the finished corrected life cast we will create a master mold of the face. A negative mold of your actor means you can create many positive molds to work on at the same time. You can make smaller molds such as the nose or chin.  To make the master mold: The first layer of silicone is very runny. Mix the silicone according to the info on the tin. For this mould I used Platsil 10 (I tend to use it for everything) which has an easy 1 to 1 mix. For the first layer I mixed 50 grams A with 50 grams of B. As you can see I have drawn a red line on the board around the head. This serves as a guide on how far out my mold should extend. Later we will be drilling holes through this part to keep the mold together. It is very important to get it wide enough for this. Brush on a few layers of thickened silicone. I still mix 50/50 by weight but add about 10% Poly fiber to the mix to make it less runny. You may use more or less any silicone brand for this.  To stay safe stick with the same sort of silicone that you will cast your final pieces in. For this cast I used Platgel 10 from Polytek thickened with Poly Fiber II also from Polytek. The finished silicone skin is about 1 cm thick and weighs about 300 grams. The silicone should be fully cured before you go on to the next step. Since the silicone is very soft and won’t hold its shape it needs to be supported on the outside with about three layers of plaster bandage. Let the plaster set for at least 30 minutes before taking it apart.
Here is the master mold ready to be cleaned up and then filled with urethane. The urethane used in this demo comes from Ebalta and is called SG130 and PUR11.  This system is a very simple 1 to 1 mixture ratio (weight or volume) and a three minutes pot life which makes it possible to make your molds with an incredible speed.  These materials are incredibly strong and still a bit flexible which makes them more or less impossible to break. The urethane system does not give up any bad smells so it is easy to think they are harmless but repeated contact may cause allergies. Always work under forced ventilation or use a mask with the appropriate filters. Have your whole work area strongly ventilated so you will not be exposed to any dangerous materials.  Skin contact with the uncured materials can also cause allergies so gloves should be worn at all times. Buyers in Sweden can get this material from   MD Komposit   For other countries please check  Ebalta website Polyfiber II from Polytek Thickener for many materials Strengthen the urethane so you will be able to bolt the molds together strongly. I laminate it with two kinds of fiber glass. Here you can see the fiber glass flocking. Every little strand of glass is about 1 cm long. And a fluffy Fiber glass tissue that absorbs urethane easily.  The normal boat making fiberglass mats that you use with polyester will not work with urethanes. They simply don’t get enough time to soak into the mat before the material is set. You should cut this in 3-4 cm wide and 10-15 cm long strips for easy application later. The positive face mold will be made in 4 layers of urethane. Since the master mold is made from silicone there is no need for any release agent so you can get started right away.  Step 1 : For the first layer pour up 75 grams of the A component of the urethane in a paper or plastic disposable cup and thicken it with 10% (7,5 grams) of Poly fiber II and stir that until it is fully mixed in. Then add 75 grams of component B and stir quickly until mixed fully. Using a disposable brush, cover the whole surface with an even layer of urethane. This stuff starts to set or harden very quickly (3 minutes working time!!)  so it takes a little while to get used to working with it.  It is  great once you get to know it! A  mold can be done in almost no time compared to plaster. Step 2: The second layer will include our first fiberglass. For this we will use the fiber glass flocking. After the first layer is dry allow to set for about 30 minutes. Mix up a new batch following the same recipe as the previous layer. Apply in the same way as before but as soon as you have brushed it out; you start adding fiberglass flock to the surface using your gloved hands to create an even layer of it. Quite often I actually wear two pairs of  gloves when doing this since they can tear quite easily. This is a close up of the fiber glass flocking. Wearing vinyl gloves, pat the flocking down so it is laying neatly on the surface. Any flock that is sticking up will  hurt you later. Be careful not to trap any air under the flocking. All air pockets will be weaknesses in the final mold.
Step 3: The third layer is once again mixed as the first recipe and poured into the mold. Urethane moulds  (21) But this time instead of flock we take the strips of fiberglass mat/tissue and push into the wet urethane. The layers should overlap a little bit and cover the whole surface. Step 4: To soak the matting with urethane  prepare a mix of 100 grams A and 100 grams B (no polyfiber in this mix) and simply pour it over the matting while moving it around with your gloved hands. Vinyl gloves work best for this since nitrile gloves tends to stick to the material too much. The plastic will soak through in seconds. Keep moving the material around until it starts to get sticky. You will at this point feel that you are destroying your mold by ripping the matting out.  This feeling is your sign to take a step back and let the setting continue for a minute without touching it. Now comes the most crucial moment of the whole procedure. You need to work very quickly. Using your gloved hands push the material together and get everything that sticks out to lie down. It sounds tricky but after a couple of times this step will feel like second nature to you. Keep rubbing the surface until it becomes nice and shiny. Step 5: If you didn’t get nice smooth surfaces you can always mix up a nice thick batch adding up to 20% of Polyfiber. Using the thick mixture as you would patch up a wall you can get beautiful results and a mold that is nice to handle later. Step 6: After letting the urethane set for about an hour you can de-mold it. Remove the plaster bandage support mold and then simply peel off the silicone master mold gently. Remember that this can be used many times so it should be cared for, cleaned and placed back in its support mold.
Be careful!! As you can see the positive mold came out beautiful but needs a lot of trimming around the edges. Step 7: Urethane resins may under high temperatures release toxic fumes so when working with power tools such as saws, drills or sanding equipment I always wear a gas mask to make sure that I do not get exposed to anything bad. Normal sandpaper works great too. A nice finished positive face cast in urethane. Scultpting a new face on the positive: Sculpt on the mould by brushing a thin layer of melted plasteline clay on the positive. This will form a well adhered clay layer that you can work on top of.  One of the best ways to melt clay is in an in-expensive rice cooker. It will melt the clay plus keep it warm for the rest of your sculpt session.  Do not lock the rice cooker on “cook”. This will kill your rice cooker and may be a fire danger to you and your whole studio! Since this tutorial is about mould making and not about sculpting we jump ahead in time: Now the sculpt has been made and holes have been drilled in the eyes and around the outer edge of the mold.  The holes are there so you will know where to drill later and not drill into any sculpted parts when you are drilling the holes thorough the negative. To put the molds together when you later fill it with silicone you will need a place where excess material can escape.  This is called the overflow area. You create a void in the negative mold by adding a thick layer of clay outside of your sculpture. Here I am using melted clay from the rice cooker to form the first layer. Be careful! This is hot and if you get it on your skin, your skin will come off with it. Ask me how I know this!!! Yes, I have been uncareful and had a big piece of my skin on my arm come off.Very painful! This clay layer should have a sharp 90 degree cutting edge about 2-3 mm away from your sculpture. Almost done! The drilled holes have been filled with clay. The whole positive has been attached to a board with more clay. Make sure that no urethane can leak in underneath the positive. Add small square clay pieces that will create nice little holes where you can open the mold.  A thick line of red permanent marker around the outer edge will make sure that you can find the seam when you take the mold apart.  Instead of filling the drill holes with clay you can put your bolts in them and seal them with clay from the back. The downside of this is that it might be more difficult to make the negative mold since you will have to work with the bolts sticking up. But on the plus side, the mold dries without any chance to move or warp. The molds with the best precison that I have made has been with the bolts already in at this stage. You will have to weigh up the pros and cons before choosing what to do!
The overflow should be as smooth as possible to avoid difficult removal of your prosthetics later on. Here you can clearly see the little clay bits for the screwdriver to fit in later. Yes, you have to think backwards when making molds. that is part of the fun! Before starting the mold apply a small amount of release agent to both sculpture and to the surrounding board.  You can use Epoxy Parfilm 5 or a wax spray. Both work very well and aids the cleanup of the molds later.  Layer 1: Urethane Mix 75g A and 7,5 grams Polyfiber II until smooth Mix with 75 gram B  Apply this gently with a cheap soft brush that does not not loose any hairs. You do not want to ruin your sculpt! But the brush will be destroyed!! Layer 2: Thick urethane Mix 75g A and 7,5 grams Polyfiber II Stir well until smooth. Mix with 75 gram B  Apply with a new brush When layer 2 starts to set add fiber glass flocking until the surface is covered and keep patting it down until flat and dry. Layer 3: Thick urethane Mix 75g A and 7,5 grams Polyfiber II as usual until smooth.  Mixed with 75 gram B  Pour over until the flocking is soaked. Keep moving it around until it starts to thicken. Keep moving As it starts to thicken I start pressing the glass mat into the surface.  Most mats have one side with little loops on it. Make sure these face in! Keep adding mat until everyting is covered well. If you leave an area empty that area will be very weak later! Layer 4: Liquid urethane Mix 100 gram A with 100 gram B Pour all over the fiber glass mat with gloved hands. Rub and pat until nice and smooth.   If you have a thick layer of matting you might need another layer of the same mix!! Use your common sense here! I don't know everything and it is frustrating!!
Layer 5: Very thick urethane for the surface fix Mix 75grams A, 15 grams Polyfiber II with 75 grams B. Add with a spatula or gloved hands until the mold looks nice.  When you are done the mold should be left to fully cure for a minimum of a few hours before proceeding.  Rushing will warp your molds. All your work will be destroyed.  Again, ask me how I know this??? I have stressed too many times and destroyed my molds.... Why will I never learn? Waste material has most likely run down on the sides of the mold. If you followed the advice of sealing the sides nothing will have run underneath the mold and clean up is easy. Use a vibrating saw to get the cleanest cuts. The red marker line drawn all around the edge of the positive now comes in handy.  As you see the line becomes visible when I cut.  When sawing into urethane the temperature of the material gets quite high and as a precaution I always wear a full gas mask to protect both my lungs from gases and eyes from debris. And don’t forget to protect your hearing too! You only have one life! Read my safety tips under the info menu! Before you take the mold apart it is important that you drill holes through the new negative too.  Start drilling straight through the clay filled holes on the bottom half and keep drilling all the way through. Do not forget the eye holes and any other holes that you may have added for stability. More drilling. Important note for this picture and some of the others The only reason I am not wearing a gas mask here is because I had to talk while doing it since I was teaching during the photo shoot. NOT good!!!  Gases might come while drilling too. So stay safe!  My studio is actually built like a forced ventilation room and I was most likely safe here too but I do not like taking chances and neither should you! The moment of truth is here! Most face molds should always be opened from the top. The reason for this is the nose. If you open the mold from the bottom your negative mold will most likely get stuck on the nose causing damage.  Here the little clay squares at the top of the molds comes in handy. They provide a perfect place for screwdrivers to fit. Open the mold evenly. If you open for example from the right you will put unnecessary pressure on the cutting edge on the left hand side. Rushing this step will only make failure a reality. To open a mold can be frustrating and time consuming. The clay inside the mold is hard and needs to be pried open slowly. This was really hard work! It stuck together quite hard.  Sometimes it can help to submerge the whole un-opened mold in warm water to soften the clay a bit. Finally after about 15 minutes this molds opens without any damages or undercuts.  Don’t let this be a guide for how long this should take. Molds have sometimes taken me a full day to open. Clay can stick to both the positive and negative. Separate the clay used for your face sculpt from the overflow sculpt. The reason for doing this is to give you a rough idea on how much silicone is needed to fill your mold. Cleaning the mold is a very sad chapter of this tutorial. It takes a long time with a lot of elbow grease to get it clean. First use soft sculpting tools and wooden spatulas. Then scrub the mold clean with dish brushes, tooth brushes or anything relatively soft.  Add lots of Fairy liquid as you are scrubbing. Try to avoid using any solvents.  Sometimes though textures refuse to let go of the clay. Then clean the molds with a bit of solvent that will dissolve your clay. This particular sculpture weighed 255 grams which means that I will need about that amount of silicone too.   If you are using Chavant clay for your sculpt then you should look above in the menu for our Android app for your phone or tablet. Then you will know exactly how much you will need! When sanding by hand you do not reach the temperatures that will create toxic fumes but you have to use a mask to protect yourself from the dust.
Bolting the molds together can be a tedious task. The silicone piece I am making here is a theatre piece. Silicone is easier to produce than foam latex and is fast to apply during the performance. While doing prosthetics for a theatre you need to have 5-7 new pieces every week. Most of the time tomorrows prosthetic will be made during a pause in the evening performance. Being fast and having a high rate of success is of greatest importance when working for theatre. Before applying the silicone barrier layer, spray a thin coat of Epoxy Parfilm on both mold halves. For this demo used Platsil 10 from Polytek. This silicone has a very fast cure and almost never fails.   Step 1: Mix up a small batch of Platsil 20 grams A and 20 grams B in a small cup Add a small pinch of 2 mm Persian Red (Pantone 187C) nylon flocking. The flocking will give your pieces a lovely lively skin tone and that little unevenness will make it appear real. Now we need to create the skin for the soft prosthetic. These type of prosthetics are called gel filled prosthetics and since they are filled they need to have an outer layer, like a balloon that is filled with air. Here we use a solid silicone as the "balloon" and a sticky silicone gel as the "air". Step 2: Use a polyurethane sponge and your gloved hands to evenly spread it all over the surfaces of the mold.  This thin silicone layer will form an outer skin on the prosthetic. This also creates thin silicone edges that we will glue onto the skin of the actor.  It is very important to never use anything made from latex when working with silicone. The latex will inhibit the silicone and it will never cure. Step 3: When this is  dry we are going to make the soft filling for the silicone prosthetic. For the filling use a third component to the mix. This is called Deadner and was developed by the very talented Gordon Smith. The Deadner is a softening agent and slows the silicone in its reactions.  You can add anything from 50% up to 250% deadner to your mix but I have found that a mix with 100% deadner is perfect for most of my theatre uses. Start adding pigments.  For a long time my preferred pigment was mashed grease paint makeup and flocking. Now I mainly use silicone pigments from Mouldlife.co.uk and 2 mm Persian Red (Pantone 187C) nylon flocking from www.flocking.biz Test color intensity by dipping a clean wooden spatula with a black dot drawn on it into the colored silicone (Only Part A and Deadner so far). Lift up until you just see a soft dot after about 5 seconds. If the edges of the dot are clear then add more pigments.  If you can't see the dot at all after 5 seconds you have added too much.  Pigments will color your silicone into believable skin tones. There are a number of different products. I use a lot of Mouldlife pigments. Mainly dark flesh pigment since this is creating a good base for caucasian skin tones. I think the light flesh pigment is a bit too pink for most uses. The remaining 62, 5 grams of B I will add after the pigments are in.  So when you are happy with the color finish mixing in the remaining part B silicone.  Be careful not to get too many bubbles into the mix. Pour into your mold from as high you can reach in a small trickle. This will break bubbles in the silicone and get you a nice translucent silicone.  But if you have access to a vacuum chamber I really recommend this instead! Then your silicone will  be perfect every time. For a 100% deadner the mix is: 1 grams A,  1 grams B (total of 2 grams silicone) and 2 grams of Deadner.  For a 200% mix it would be: 1 grams A, 1 grams B (total of 2 grams silicone) and 4 grams of Deadner.  To mix the 250 grams batch of 100% deadner: To mix the 250 grams batch of 100% deadner mix that we need for this mask mix 62,5 grams of A with 125 grams of deadner. Slush the silicone in a thin layer around the mold. This will also ensure you have no trapped air bubbles.
Gently put your positive mold down in the negative mold. Do not rush this! Let the positive slowly sink into the silicone and push any last remaining bubbles up and out. Set your drill to the lowest torque setting. Bolt your mold together using wing nuts on the back.  Put every other bolt on the opposite side of the molds. This will put an even pressure on the edges of your mold. These molds are very strong but if you over tighten the bolts it may still break. When you are done just leave your mold to cure for 30 minutes to an hour depending on the room temperature.   Since the silicone we are using is a platinum cure silicone it is easy to quicken the cure by raising the temperature i.e. in a low heat oven. 60 ®C (140®F)  is usually good.  Doing so will decrease the cure time by half. Add more tension slowly to get your edges as thin as possible. You have at least 5 minutes to do this so take your time!  Then you let the mold rest and cure for about an hour. It is most likely to dry in 30 minutes but if you open it too soon it might be destroyed. Another scary but intensely fun part is to open the mold for the first time. To aid in opening, spray water into the openings. This acts as lubrication.  I am not really sure if that sounded OK... You have to read it with nothing else than mold making in your mind!! Let the tension from the sticks and screwdrivers work it's magic slowly!! If you try to force the mold open the silicone piece will break! And maybe the mold too! Ouch! That would hurt! Lars’s first fitting of the mask. The flashing is still intact.  Once happily out of the mold, wash the piece with soap. Put the piece back on the positive to dry.   Very important! Never use any powder at any time of de-molding a silicone piece. You will lose the pieces transparency. The edges will be very difficult to blend with the skin.  This is difficult for anyone who has worked with foam latex since there you need to use powder. I struggled for years to put the powder away.. But of course, if you are taking this to the next level and use a plastic skin (like Super Baldies) instead of a silicone one you need to bring the powder back out again. But that is another tutorial!! In the next 40 pictures you will see various uses of urethane molds from some of our productions. Here is just a test sculpt on a positive. Same sculpt with the flashing sculpt added. DSC 2983
First runny layer of urethane. Somewhere in the middle. DSC 2992 Sometimes when it will be impossible to know where to drill you have to add the bolts before starting. How could you drill from the inside of a small head?? On this whole head sculpt you need to add a vertical flashing to keep the nold parts separate. The dividing wall is water clay and the sculpt is plastilene so they won't mix or destroy each other. You do need to spray the water clay with some type of coating before starting the mold. DSC 3167 Check the beginning of the tutorial to find out which step this is. Check the beginning of the tutorial to find out which step this is. Check the beginning of the tutorial to find out which step this is.
Check the beginning of the tutorial to find out which step this is. Check the beginning of the tutorial to find out which step this is. Check the beginning of the tutorial to find out which step this is. Check the beginning of the tutorial to find out which step this is. The fibre glass layer The finished mold. I wonder if it will come apart?? DSC 3200 DSC 3202 Dreading the clean up............ DSC 3205
DSC 3208 Nice and clean mold ready for silicone. First half on And the the two halves bolted together around the positive What it looks like without the positive inside. If you put it like this you could make a slush cast mask in here. Making molds together with My Maniette. All the molds from a big production. Too many hours were used to make these.. Ohhhh. The memories. This was a big mold for a corpse I made for a film. The silicone has been brushed in both the front and back before putting them together. I like this way of doing it since the risk of bubbles is much less. Just remember to mix all the A component of the whole project with pigments before starting otherwise you will not be able to color match the front, back and seam!!
The back part. Sometimes we don't just make makeups. This was the handle of a silicone and bamboo fire poker that was used to beat a guy to death in a theatre play. Silicone is much safer than cast iron!! So this is the mold. And the top bit. On this project I added the bolts already at the first half of the mold to see if the precison would get better. And it did so I will most likely always do this in the future. 2012-10-07 12.14.26 On the end product there were hardly no edges! This is a PDF copy of the whole article. The pictures are small but might serve a good memory guide while working in the studio.  Use the "Original" button on the right to save it to your computer. Safety always have to come first! If you can't protect yourself properly then avoid the material! Most of the time I use the Sundström SR-200 full face mask with a ABEK1 Hg P3 and a P3 particle filter but it all depends on the project!  Use the top 1:1 icon to zoom in for easier reading. The following documents come from Sundström company   http://www.srsafety.com/ Here is the Safefy information document as last image but in pdf for easy printing.  Use the "Original" button on the right to save it to your computer.   http://www.srsafety.com/ These are the filter recommendations from Sundström 2013. Always make sure that you check the current recommendations and what your mask manufacturer recommends.   http://www.srsafety.com/
These are the filter recommendations from Sundström 2013. Always make sure that you check the current recommendations and what your mask manufacturer recommends.  http://www.srsafety.com/ These are the filter recommendations from Sundström 2013. Always make sure that you check the current recommendations and what your mask manufacturer recommends.  http://www.srsafety.com/ Here is some recommendations for choosing a filter.  But please don't take my word for it!! I urge you to talk to experts before doing anything with chemicals.   http://www.srsafety.com/ Here is some recommendations for choosing a filter.  But please don't take my word for it!! I urge you to talk to experts before doing anything with chemicals.   http://www.srsafety.com/