Animation World Magazine, Issue 2.11, February 1998

At Last, Foam Puppet
Fabrication Explained!

by Tom Brierton

This metal armature, left, became the final praying mantis puppet on the right when encased in a cast foam latex exterior. All elements were constructed by Tom Brierton.
This metal armature, left, became the final praying mantis puppet on the right when encased
in a cast foam latex exterior. All elements were constructed by Tom Brierton.
Photo courtesy of and © Tom Brierton.

Stop-motion puppet animation is surely one of the most unusual art forms in the world. In cel animation, one must master drawing and performance. In computer animation, one needs to acquaint themselves with the technicalities of the mouse and keyboard, as well as performance. While these two animation disciplines require talent and drive to achieve successful animation, stop-motion is unique in the animation field in that it encompasses a number of disciplines to achieve a final end. Design, armature machining, sculpting, moldmaking and casting, painting and detailing, lighting and cinematography, and of course, performance animation, are the primary skills required to master this wonderfully magical art form. While it certainly isn't necessary for a single individual to master all of these disciplines (and there are few stop-motion animators who have), there is no reason why one cannot attempt to do so, and have fun in the process.

I have designed this article as a cursory description of the stop-motion process. It will deal with the necessary disciplines for creating a stop-motion puppet. The disciplines include: design of the puppet, armature machining, sculpting, moldmaking and casting, fabrication and detailing. I will be leaving out discussions on character animation as that process is an article in itself. I have also written in a cursory fashion, because, quite frankly, a single book could be written on every step of the stop-motion process. It is beyond the scope of this article to attempt to write a volume on each discipline. For the uninitiated, they can perhaps walk away with a better understanding of stop-motion, and use the following information as a point of departure for their own animation endeavors. As stop-motion legend Ray Harryhausen once told me years ago, "self-experimentation will be your greatest teacher." I would like to pass on his wise counsel, with the assumption that those who read this article will like-wise, take this information and experiment for themselves.

Design With Attitude
Many puppet animators start with an idea for a creature to animate. The puppet can be inspired from an animal, art, mythology, a book, music, or one's own imagination. Regardless of the source, the ultimate objective is to translate the idea of your creation to the actual tools necessary for creating the puppet. I am very fond of the minotaur, a monster from classical Greek mythology, but up until recently, I had never created one as a stop-motion puppet. Determined to do so, I proceeded to research the problem. Research is usually the first step, particularly if one is creating a creature that actually exists in real life, such as animals or insects. Since the minotaur is a hybrid animal incorporating the body of a man and the head of a bull, I searched for photographs of human males and of bulls. Since the minotaur was supposed to have been a dangerous animal, bloodthirsty and violent, the idea was to design the character so that it is indeed imbued with these attributes. To design the minotaur with skinny legs, a pot belly and short stubby horns would hardly qualify it as a frightening monster. Consequently, the solution decided upon was to design it with a hulking body: huge arms, rippling with muscles and veins, sinister deep-set beady eyes and long, sharp horns. In short, try to design the character you want, by incorporating into its design physical attributes that would heighten and augment what you wish for the creature to convey. If animated properly, its performance will even magnify its appearance. This principle of creature design plus character animation is, in some ways, rather similar to the film music principle, which states that if, for example, two lovers are kissing, then coupling that image with romantic music will heighten the affectation (emotion) of the scene. Conversely, the image of a valiant, but slain warrior, combined with 'sad' music, will impart a feeling of sorrow. Design your character around the 'affectation' of how you want the viewer to react to it. Since I wanted the viewer to react to my minotaur with fear, I designed it accordingly.

Finally, once I felt that sufficient research had been done, and enough photos and reference material had been collected, I proceeded to draw up dozens of design concepts in pencil, pen and ink, and color renderings. The next step is designing the mechanics of the armature.

This armature has more than 20 individual joints.
Photo courtesy of and © Tom Brierton.

This armature has more than 20 individual joints. Armatures: The Insides
Back in the early '70s, when I first started learning how to machine armatures, I went out to the local hardware shop and bought miscellaneous stuff like door linkers, washers, L-brackets, plastic balls with rods on them and such that I could throw together to try and simulate a stop-motion armature. While this was all good training and experience, the armatures I ended up with were strictly amateurish at best and could never have been used for anything other than decorative pieces in my room.

Over the years, I've learned the techniques and tools of the trade for designing and machining a technically successful stop-motion armature. My philosophy in machining a competent armature is that there really are no shortcuts, I'm afraid. Any compromise in the machining of the armature would cause one to end up with parts that would, at best, be substandard and hence, unusable for stop-motion animation. I could advise to go ahead and throw something together with found parts from a local hardware store, but this would really be more of a regression in one's professionalism, rather than a progression. I could tell you that you can slap together an armature from found parts and it would work really great, but from personal experience, and after almost 24 years of experimenting with different things, I've pretty much discovered what will and won't work in armature construction. Armature machining is a wonderful art form in its own right, even apart from stop-motion animation. Often-times, when people come by my studio and see my armatures, they are quite aghast when I tell them that the armatures will eventually be covered with foam. Many people prefer that they be placed on display just as they are!

Once the design of the puppet is finalized, I make a detailed line drawing of the creature, in front, side, and top elevated views, in the actual size that the puppet will be. After that, I lay a piece of tracing paper over the drawing(s) and I sketch out the mechanics of the armature directly onto the tracing paper. This way, I will know what the exact size will be for the armature part(s) once I prepare to machine it. Since armature parts can't be found anywhere, but have to be custom-made for any particular puppet, I then take each armature piece that makes up the armature itself (from the littlest finger all the way down to the toes) and do a detailed mechanical drawing, on graph paper, of each armature piece. Then I take these detailed drawings to the lathe and mill and machine them out. Depending on the complexity of the armature, and how many pieces there are, an armature can take anywhere from one to eight weeks to machine. I just finished off an armature for a velociraptor which took me about four and a half weeks to machine, plus an additional week to figure out the mechanics of the armature and draw out each piece individually on graph paper.

I don't know how much money you're willing to spend, but a person can get the necessary tools to begin machining successful armatures for about US $700. Obtain a catalogue from a company in San Marcos, California, USA called Sherline Products, Inc. Sherline manufactures miniature lathes and mill column attachments. Their phone number is 1-800-541-0735. Their lathes and mills are top-notch, roughly the size of a large sewing machine.

Putting It Together
Before putting an armature together, you need to become familiar with the various types of joints. There are basically six:

Hinge joint
Swivel joint
Dowel joint
Universal joint
Ball and socket
Collet joint

I use hinge and swivel joints primarily. Hinges are very useful for knee, elbow and spine joints. Swivels are great for pronating and supinating at the elbow and for joints just below the hips and knees. Swivels are generally connected to a hinge joint and work off of the hinges.

Probably one of the most frustrating and difficult aspects of building an armature is the rod-to-bearing solder attachment for ball sockets. A very good solution was described to me by stop-motion animator Paul Jessel, which I will pass on:

After the bearings have been drilled out on a lathe, they are placed on a heat-resistant surface. The materials you will need are:

A small butane torch (get at a Radio Shack, electronics-type store)
Extra propane tanks
Silver solder
(The best can be bought at: L.B. Allen Co., 725 N. Central, Wooddale, IL 60191 USA The telephone number is: 1-708-595-2600)
A helping hand (also at a Radio Shack, electronics-type store)
Solder flux
X-acto blades

Place the bearing onto your surface. Shave off pin-head sized solder with the x-acto blade. Be careful not to cut yourself! Lubricate these solder pieces with flux and drop them into the bearing until you have enough that brings them close to the top, but not completely. Take your rod which will be the same diameter as the bearing hole, or you can turn it minus a thousandths of an inch to help it slip better into the bearing, and lubricate the tip with flux. Let it set for a minute, then put the rod into one of the clamps of the helping hand and tilt the helping hand arm so that the rod is balanced onto the top of the bearing hole above the solder. The helping hand should be balancing on the back of its' base. Now, turn on the torch and heat the ball. The solder inside the ball will go soft after a few seconds depending on the size of the bearing. Naturally, small bearings will heat faster; larger bearings will heat slower. Once this happens, the weight of the helping hand will force the rod down into the bearing. If it doesn't, I very gingerly tap the top of the rod with a small hammer. Let the rod-to-bearing assembly set for a few seconds, then cool it under some tap water, and clean it off with a mild soap. Sometimes, when the rod goes down into the ball, if you've placed too much solder inside the bearing, extra solder will flow up and out of the hole and onto the rod and/or bearing surface. If this happens, wait for the assembly to cool, then take your x-acto blade and scrape off the residual solder. Prior to soldering, I like to take the rod and, using the lathe, cut a tiny groove at the tip of the rod at the end that will go into the bearing. This way, when the rod goes into the ball, the solder sets around the groove and helps the rod to sit better and more firmly inside the ball.

Many small joints and limbs are created for one
four-legged animal puppet.
Photo courtesy of and © Tom Brierton.
Many small joints and limbs are created for one four-legged animal puppet.

Patience Is a Virtue
If a joint is machined without any real thought or care going into it, you're likely to get a joint that pops or ratchets when you try to move it. This can be absolutely maddening when you're animating a puppet and all of a sudden the armature pops or breaks. Unless you're using a frame grabber, you've really created a problem for yourself because now you will need to repair the puppet and start the shot over again. Machining tolerances of armature parts need to be in +/- thousandths of an inch and some armature machinists machine in 10,000ths of an inch! The thing of it is: the process of actually machining an armature really isn't all that difficult in terms of tool usage. In other words, you don't have to have a degree in industrial design or math to use a mill or lathe. The only thing that I find difficult about armature machining is the need for patience. If I hurry, I will invariably overturn a part or overdrill a hole. Slow and easy, in my opinion, is the key to successfully turning out parts for a decent armature.

Obviously, once again, you're going to need supplies for the next step and here is a list:

Number 2024T-356 aircraft aluminum (most machinists use this grade of aluminum)
Hex head screws
Phosphor bronze washers (used in hinge joints)
Drills and various jobbers
Number 302 Grade 100 stainless steel ball bearings (some machinists use 440 bearings)
Shoulder screws (sometimes called shoulder bolts)
Dowel pins
Slotting saws
End mills
Ball end mills
Milling cutters

Slotting saws, milling cutters and end mills, both straight and ball, are actually used to sculpt the piece of aluminum into the shape that you want. Slotting saws and milling cutters are held in a saw arbor, which in turn is held in a mill collet, which turns on the mill. The shank diameter of an arbor used on a Sherline 4000 mill is generally a half-inch, so buy a mill collet that will hold a shank that's at least that diameter. (Don't worry. Sherline has everything that you'll need.) End mills are the most frequently used cutter for metal sculpting. They are held in an end mill collet. Collets, whether it's an end mill or saw/cutter collet, actually hold the cutting tool secure in place while one performs the machining operation.

As I said, the first thing you should do is order the Sherline catalogue. It's cheap and will give you an idea of the tools that are necessary for you to have in order to build a decent armature. Also, order a catalogue from J & L Industrial Supply. They're a U.S. distributor of various machining knick-knacks. Their catalogue is free, and huge, so call 1-800-521-9520. McMaster-Carr is another one-stop shopping place for any and all supplies, except bronze washers. For a catalogue call 1-630-833-0300. For phosphor bronze washers, call Seastrom Manufacturing at 1-800-634-2356. Phosphor bronze washers are used in hinge joints. Measuring tools which you may also need include micrometers, surface gauges, a dial indicator and a dial caliper.

Next Stop: Sculpting
You can go to just about any bookstore and find books on sculpting. For stop-motion models, most people in the industry use a brand of clay called Roma, which comes in various grades ranging from extra-soft to hard. I use Roma #3, which sculpts nicely and is less prone to cracking over time. To get really smooth textures, I use a paintbrush and brush a little rubbing alcohol, or better, rubber cement thinner, onto the surface and blend the clay with either a tool of some kind, or my finger. I can't really tell you much about sculpting because, as are most things in this world, it's really learned from practice.

Rather than sculpt the clay directly onto the armature as some animators do, I prefer to make a heavy aluminum wire armature (16 gauge is good) into the exact shape and scale as the actual machined armature. This way I don't have to clean the clay off of the metal armature which can take quite a long while to do. Plus, Roma has somewhat of a nasty corrosive habit of, over time, eating away at the aluminum surface. Another way is to wrap the armature with clear, plastic, food wrap. This keeps the armature clean and clay-free for when you're ready to take the sculpture out of the mold and strip the clay off of the armature.

This minotaur puppet armature was covered with plastic
wrap before the clay figure was sculpted on top. Later it
will be cast in a mold.
Photo courtesy of and © Tom Brierton.
This minotaur puppet armature was covered with plastic wrap before the clay figure was sculpted on top. Later it will be cast in a mold. Photo courtesy of and  Tom Brierton.Mold Making: Two Methods, One Puppet
There's basically two main ways to finish a puppet in foam: the foam-injection method, which uses the clay sculpture, and the build-up method, which doesn't. Most puppets I know of are actually a combination of the two. For example, they have a foam injected body, then surface detail like muscles and hair are built up, literally sculpted, over the armature using the build-up technique. For the skeletons in Jason And The Argonauts, Ray Harryhausen had his father machine the armatures, then Ray actually sculpted the models using the build-up technique. He applied rubber, mixed with cotton, directly onto the armature and after it dried, he added a coat or two of rubber to smooth out the sculpture. Jim Danforth also used the build-up technique for the mother dinosaur in When Dinosaurs Ruled The Earth.

A mold needs to be made of the clay sculpture before you can inject foam rubber into it for oven curing. The mainstay of mold-making material for a stop-motion puppet is a product called Ultracal-30. Ultracal is a little like plaster, but denser, and, unlike plaster, it reproduces sculpted textures extremely well. It is also less likely to shatter like plaster if accidentally dropped on the floor. Utracal is almost like concrete, but isn't nearly as heavy.

Mold making isn't very easy. It takes a lot of practice. Most molds are anywhere from two to four or five pieces, depending on the anatomy of the puppet. For example, if you're making a human shaped puppet, a two-piece generally will do the trick, one for the front and one for the back of the sculpture. However, if your human shaped critter has a long tail, then a two-piece mold will need to be made of that as well. If it also has wings, then another two-piece mold will need to be generated. So, you end up with six pieces for your sculpture of a human shape with a tail and wings. In my opinion, creating the six molds separately is the only practical way to do this. Then, after all the foam rubber for each respective mold has been properly cured in the oven, they are carefully pried out and attached to the armature (wings to the back, tail to the rump). Then, exposed seams can be covered using the build-up technique with additional rubber that cures at room-temperature. I get my Ultracal-30 from a supplier in the Chicago area called Art Studio Clay Co. They can be reached at 1-800-323-0212. However, you might also be able to find some at your local art supply store.

Though there are a number of ways to apply the mixed Ultracal-30 to your clay sculpture, I generally do the following procedure for pouring the mold. To pour one-half of the mold first, I lay the puppet down, anchored to a piece of wood with screws in its feet to support it, and place the reclined sculpture into a square wooden box. Mix up the Ultracal and pour it into this wooden box, just covering one-half of the sculpture (in this case, the lower half, letting the Ultracal rise up to meet it.) Let this half of the mold dry first overnight, until it's hard and dry to the touch. The next day, rub mold releasing agent on the mold surface and then pour the rest of the Ultracal to complete the two piece mold. Believe me, this is much more difficult and time-consuming than it sounds, so be prepared to make some mistakes, and practice a lot.

All of your sculpting supplies can be purchased from Burman Industries in Van Nuys, California. Their phone number for a free catalogue is 1-818-782-9833. You can also buy instruction tapes on mold-making, sculpting and painting from them.

The build-up technique calls for simply sculpting foam rubber mixed with cotton, directly onto the armature into the shape of the creature's musculature. Then, thin sheets of dried foam rubber (detailed with scales, hair, etc.) can be wrapped around the muscles. I'm currently sculpting my minotaur in this fashion. It isn't as easy to do as foam-injection, but with practice the results can be quite wonderful. Marcel Delgado sculpted the Joe models in Mighty Joe Young in this manner as well.

Almost Done: Foam Casting
Foam casting, in my opinion, is the hardest step in the foam-injection process. Because foam is extremely difficult to mix and set properly, it takes a great deal of patience and experience. Be prepared to spend a lot of money making mistakes. You'll get it eventually, though.

R&D Foam Latex used to be the most popular and frequently used product, however it is no longer available. Kryolan is another brand which I've used with good results. There's a supplier in England and Burman also has their own brand. Whichever company you decide to go with, they will send you detailed instructions on how to mix it.

This technique is called foam-injection because strategically placed holes are drilled into the molds. The armature is wrapped with a flexible material (I use Saran Wrap, a clear, plastic food wrap) and carefully lined up inside the mold. This is done because foam latex rubber has a kind of ammonia base, which smells bad and causes corrosion on metal. Always wear a face mask when working with foam. The mold is clamped shut and sealed tight with belt clamps which can be purchased from Burman's. Then the mixed up foam is poured into a special foam injection gun which can also be found at Burman's. The foam is then injected into the mold. This has to be done quickly, because the gelling agent that is added to the foam can sometimes cause the foam to set up inside the gun, thus making it impossible to inject through the nozzle. In which case, you'll have to re-mix and pour more foam. Foam doesn't have a very long shelf life; four to six months tops if stored in ideal conditions. It needs to be used as soon as you get it. I wouldn't buy the foam until your molds are already done. Once the foam is properly injected, the mold is placed in an oven (or kiln) and allowed to cure for a few hours. After sufficient curing time, the mold is taken out and allowed to cool at room temperature, usually overnight. The next day, very gingerly pry the mold apart, and if all has gone well, you will have a foam rubber representation of your original clay sculpture surrounding the armature. Voila! All that's left now is detailing (hair, fingernails, eyes, etc.) and painting.

This armature is for
a genie character.
Photo courtesy of and
© Tom Brierton.
You might be asking yourself, "Why go through all this trouble making a foam puppet, when I can just sculpt the puppet in clay and animate it that way?" Foam latex offers a tremendous plus in that, when it's properly cast and painted, it uncannily resembles flesh and muscle, an extremely difficult effect to achieve in clay. However, probably the single largest advantage of a foam latex puppet is in what I call "the mush factor." The armature has to be fairly tight to hold positions during animation. When you're animating a puppet made from clay, once you push an appendage, like an arm or leg, to its next position, you will invariably disturb the clay as well. Since clay doesn't spring back into the shape it originally was, the surface of your sculpture will pixelate when you project the animation back in dailies. Foam, on the other hand, when you grab and then release the puppet, will repeatedly spring back into its exact shape. This is crucial in a time-lapse process like film animation. You could try to re-sculpt a clay puppet if you've inadvertently disturbed the surface, but this takes time, and chances are you'll never get the sculpture precisely the shape it previously was. Foam alleviates the problem.

I hope all this helps. Let me know how your experiments go and if you need any help!

Tom Brierton is currently based in Chicago, Illinois and works free-lance as a stop-motion animator, armature machinist and CGI animator for various animation houses and a video gaming company. His interests in stop-motion animation began in 1972, when he was fifteen.

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