Flexible Polyfoam Head And One Foot Done


INTRO: Maybe this should be in tutorials, but it is a work in progress as well. Anyways... After completing my ironman for last halloween, I thought I'd try a predator. Thanks for this forum. You can learn from my mistakes of which I made many. This is NOT easy and it is not inexpensive. I got a kick out of a guy who posted looking for a complete movie-ready suit for < $1000. This damn head is gonna cost more than half that!! But that's for me, someone who's never done any of this and had to build up my inventory of materials. I get all my materials at ww.brickintheyard.com in Dallas, Tx. Except I buy Hydrocal in 100lb bags locally since it's extremely expensive to ship. Experienced builders and foam runners will be best to ignore this post; it is for those new to the craft and NOT for people who make money doing this. There is some serious talent on this site, and look elsewhere for the awesome sculpts and outfits. Mine should turn out good, and will be done by Halloween 2014, but it will NOT be great as many of these on this site are. I will take you through step-by-step fabricating of a working costume you will be proud of and will wow your friends. I give myself a year becasue I have a full-time occupation and this is a hobby and it takes hundreds of hours and over $1000 worth of raw materials, if you are new to this, and have to stock up and burn through materials as you climb the learning curve. ARMATURE: My first lesson is BUILD A SOLID ARMATURE. In order to keep costs down, I recommend WED clay, and a Hydrocal mold reinforced with fiberglass mat. The only problem with this (every way has it's pros and cons), is WEIGHT. YOUR ARMATURE NEEDS TO SUPPORT 100 POUNDS !! A Predator head is HUGE and the mold is GIANT. I used my Bob punching dummy for my first one and it buckled at the neck. I built a crappy store bought foam head with a weak attachment to a small wood stand and it broke. My third armature is below. If I had it to do again I'd buy a rigid plastic dummy like you see in most of the posts here. The pros do this for a reason.

This is a store bought foam head, drilled a 1" hole all the way up the center, and press-fit and glued a 1" PVC pipe into it, then secured to base with 3 layers: 2x4's had 1-1/8" hole drilled and cross screwed, then the 2 pieces of plywood with 1-1/8" holes offset to SECURELY fix the pipe to the base. Filled the PVC pipe and all voids with F-3. Built up head with some clay then fiberglassed whole thing with 1qt resin and mat. It does dissolve the foam head some but it was VERY secure and supported the weight fine. Put a crossbar on the front and back leg so you can tip it forward and backward when molding later and it won't wobble side-to-side. SCULPTURE: Use local store-bought WED water based clay. Plasticine is better but expensive and hard to find. Plus harder to work with since you have to use Naptha to wet it and clean up, but WED is easy to smooth/work/tool with water, and cleanup is with water. WED clay is $20 for 25lbs and you need 50 lbs. One lesson I learned is DO NOT SKIMP on materials. This hobby is costly, so know that going in and be prepared to buy more than you think you need of everything. WED clay will last months if you keep it in a plastic bag and keep it moist, so get a mister spray bottle. Work on your sculpture misting it every 10-15 min, put a bag over it when you're done, and you can sculpt for several weeks.

Use the pics in other posts like the one by Master Anubis, along with pics from the internet, to use as models to look at while sculpting. I don't enjoy making a lot of measurements so I just eyeball everything. My sculpts suck compared to others' around this website, but I'll show some anyways for instructional purposes. The main thing is make sure you have the overall shape right before detailing. In fact, you should make a small model of something easy to sculpt, and go through the whole process of sculpting, detailing molding, pulling a final, so you can avoid mistakes that ruin your clay positive, hydrocal mold, and cause expensive, time consuming re-do's. Once you've shaped it out, use your bare hands, wetting when needed, to smooth it out. Make sure the eyes line up with where your eyes are going to be. Make sure your model's centerline is in the center. Sculpt both sides at once. Use basic clay modeling toos available at local hobby store for details. This is my first sculpt and the mistake I made besides the weak armature, was that I did not get the overall shape right before detailing. I knew this would be a practice run going in so it was ok. Also, see those sticks holding it up? -- those are because of the suck armature having broken. Very difficult to work around those supports.
first sculpt .JPG

first sculpt  (4).JPG

I molded that one, also a practice run, and used Polygel, but decided that was too expensive and unnecessary since I could use a hard mold of Hydrocal if I was willing to part with my sculpt. That means if you use Hydrocal you will destroy your clay mold removing it, like they do on Face Off. If you can't bear to part with your WED clay sculpt, you can use a soft mold of Polygel ($$) or Silicone ($$$$). Or, if you need a hard cast positive of plaster or resin, you will need a soft mold. But, I realized I didn't need a hard positive, and I didn't have any reason to keep the clay sculpt after it was casted, so on my second try I used the Hydrocal hard mold method. Cheap and you can do it, but it has disadvantages like plaster dust (get a respirator), you have to make entire mold with one Hydrocal batch (you can do multiple batches if you use Ultracal but I couldn't find it locally), extreme mess (don't even think about doing this inside), and weight of the mold. So, a few more lessons learned on my second sculpt, and by my third one I knew the process well enough to get through it and come up with a decent final.

sculpture  (5).JPG
sculpture  (4).JPG

sculpture  (6).JPG

MOLDING Use Hydrocal and search hard to find it locally. Get 100lbs. You must have enough to finish the job. I started out with the 8lb cans you buy locally at hobby shop, then ordered what I thought was a lot of Hydrocal 37lbs and paid $45 for it and thought I was getting a great deal since shipping was free. I burned through that very quickly. Then I searched and found a concrete supply store and went and picked up a 100lb bag for $37. If you run out during mixing a batch, it will make you sick, so get 100lbs ! Tilt your sculpt back and support it very securely, making sure it will not roll off the table. You will crush in the back of your head but don't worry,that is simple to fix after the front of the mold is done, right before you mold the back. Watch the Brick in the Yard youtube videos several times before doing any particular step, and now is the time to watch the one "Moldmaking and Casting: 2 piece hydrocal head mold." Support it very well, build up to the halfway point with wood pieces or something very solid, and make a SOLID WED clay wall and take your time and pay attention to the details in the video, especially the trough-like key.

molding  (2).JPG

molding  (3).JPG

hydrocal mold.JPG

I recommend releasing liberally with Pam cooking spray. Spray it all over your clay model. Douse it. If you can't stand the minor loss of detail, then you are already too advanced for this tutorial. NOTHING is worse than having everything stick together and not being able to separate parts. Have 4-5 cans of Pam on hand at all times. Now watch the BITY video on mixing Hydrocal: "Moldmaking and casting: Hydrocal Plaster Mother Mold Process" It is easy when you know how to do it, but not knowing details is a killer. Basically, you get a pail of water and add HC to it a cupful or handful at a time, then when the HC mountain peaks just above the water line and the water absorbs up to the peak, let it sit for 10 min without stirring. It will not harden. It will saturate the plaster and then mix it gently with bare hands and there will be NO CLUMPS. You have 30 min working time. It goes through 3 stages of hardening and the first water-like stage is perfect for detailing. Then the slightly thicker phase is for reinforcing with fiberglass, then finishing and smoothing. Once you have the first half, turn your mold over, remove the wall, repair the crushed-in back, tidy up the seam, and finish the mold. Use Johnson's Paste Wax liberally on the mold flange. Keep the edges free of excess plaster or separating will be very difficult.. Let cure overnight. Separate it. It won't break much.if you put enough fiberglass near the edges. Clean it out. Pressure washer if you have one, electric toothbrush works well. This takes time. CASTING IN FOAM Make sure you have a mold strap. Have everything ready to go for the foam run.

dummy head.JPG

Have a rigid foam wig head and put clay on it to build it up to the size of your own head. This does require making measurements. I used that rope loop to tranfer circumferences of my head to the model.

dummy head 02.JPG

Have enough F-3 and PT 20. It takes about a pint and a half of PT 20 for the skin and a quart of F-3 but that's if you are experienced and know what you're doing. Get a quart of PT 20 and a Gallon of F-3. It is important that it is not cold when running foam. Make sure at least 60degF. Watch "Casting and skinning Flex Foam" and "Special Effects Tutorial: PT Flex Severed Leg." Use a respirator and gloves for this stuff. Douse the inside of the mold with Pam. Also release the foam head and clay thoroughly. Mix and then slosh in the PT 20 in the front part of the mold. You really don't have to use PolyFiber in my opinion. You will have to brush it around some, especially up the sides.

foam run .JPG

Put 2 long cut coathanger segments in the foam head exactly where the eyes will be. Center the foam head in the mold and hold it there with multiple more of these coathanger segments.

foam run  (2).JPG

foam run  (3).JPG

After about 30 min after PT 20, when it is tacky to touch, mix and pour the F-3. MOVE FAST because they aren't kidding - it sets very fast. You cannot work with it after it starts rising. You need an assistant for this step. Don't mix more than 400g batches. This stuff sticks to itself so you will have a solid 1 piece casting once done, and you will reduce waste by using multiple small batches. Fill the front half of the mold.

foam run  (4).JPG

Release the back half of the HC mold with Pam and don't get any on the F-3. Use Johnson's paste wax again on the flange of the mold to minimize seam problems. Brush in PT 20 to the back of the mold. After it is tacky, Pour part of a new batch of F-3 into the back of the mold, QUICKLY assemble it and put the mold strap on (15 seconds max), and pour the rest in and watch it expand out the top of the mold

foam run  (6).JPG

Let cure at least an hour, and demold. You have to cut up the sides with an exacto, lift up the back, chip out the foam head with a chisel. Then the sides will collapse in allowing you to demold.

foam run  (7).JPG

foam run  (8).JPG

foam run  (5).JPG

Now you have a nice solid piece that fits you perfectly and won't shift around and doesn't require an underskeleton mold. I'll figure out how to mechanize the mandibles in a future version, but this will be a static piece.

foam run  (9).JPG


I'll update after I make progress.

LEFT FOOT with SANDAL: Sculpt, again on a SOLID armature




I added the sandal and moved the buckle to the outside, then built up the clay retention wall and groove/key, then cast in Hydrocal with tons of release.




I skinned the first half of the boot with PT 20 200grams part A / 200grams part B, after a lot of release AND brushing the Pam release into all cracks. I had already made my tape-dummy foot so I mixed Propfoam 4 220grams B / 99 grams A and poured it into the first half, placed the tape dummy (which I also released), and this worked very well.

Repeated that process with the 2nd half, and ended up with a pretty major seam so it's good the film crew isn't going to be at my house tomorrow needing this for the next movie. BUT, it is pretty good, and fits perfectly, and for that Hunter out there who wanted to be able to dance or do karate in his suit, this will be plenty durable for that.





Pretty easy to mold from clay, and cast in a cup in tin-cure silicone
Last edited by a moderator:


yup thats almost how we do it
if you use mould relise on the latex befor the foam, the foam will slide out to install the mavement in the mandibles


Ahh, sounds good. PT 20 is polyurethane rubber, but releasing it will keep it from bonding to the F-3 foam filling. I'll try that. I don't want to poison my mold with Latex since I might decide to try silicone in it some day.

I was th inking of embedding the end of a bicycle brake cable in the F-3 and then operating the mandibles with those. I doubt servos would be strong enough to move that stuff. I'm a ways away from making a flexible mold to make an animatronic skeleton inside, which silicone mask would be stretched over.  Maybe a P2 next year.
Hey cmetzger, this is a darn nice post. I wish I had something like this to look at when I started. I think you underestimate yourself. A little more time on the head symmetry would have put you right there. With a good paint up it will still be a nice head. I really do like it a lot.