Saturday, May 23, 2009

Hey, lend me a (silicone) hand....

We have been diligently working on a lot of projects over here in the studio for the past few weeks and it was difficult to choose which one would be focused on for this post. I have chosen to show you how we make silicone hands.

This post is stepping everything with production up a notch, so if you have been following along with your own project you may need to purchase some additional materials before you can participate completely. In fact, to the best of my ability I will make a list of all the materials that were used for this part of the project:
  1. 19 gauge annealed steel wire (not required)
  2. 28 gauge annealed steel wire (or any other very small wire for the fingers)
  3. 18 gauge aluminum wire (twisted)
  4. Hot glue gun and glue
  5. Epoxy Putty
  6. Super Sculpey baking clay
  7. Jet Dry rinse agent
  8. Petroleum Jelly (Vaseline)
  9. Baby powder
  10. Popsicle sticks
  11. VINYL gloves (must not be latex... I will explain in a moment)
  12. An accurate weight-scale
  13. Mann Ease Release 200 (mold release)
  14. Ultracal 30 Gypsum Cement (plaster)
  15. Dragon Skin silicone
  16. Acrylic paint
The three things I have highlighted in orange are things that you will likely have a hard time finding in any local store. At first I had to order the Ultracal and the Dragon Skin online, but was fortunate enough to find the Ease Release 200 at a local arts superstore.
IF YOU ARE TRYING TO LEARN THIS FOR YOURSELF then I have one piece of advice for you. Save up some money (not much) and buy some Ultracal 30 and Dragon Skin. Just buy the smallest containers they sell; you do not need a lot to experiment with. Mastering these materials immediately puts you at a whole new level of expertise with stop motion animation. Learning to cast things out of silicone will make your animations look incredible. And besides, these are the materials the pros use all the time. There are lots of things you can spend your money and time on; in fact there isn't really a limit. But choosing to learn these two materials as soon as possible would really be a wise decision.
It won't be easy, but you don't have to learn from someone how to use them - I just researched online when I learned. You don't have to attend an animation school - I taught myself most of these techniques. All you need to do is experiment and have fun with it! Stop motion is an incredible art that is almost entirely self-taught. How unbelievable is that? Sure there are exceptions, but isn't that encouraging to know that most professional animators got to where they are now by just playing around with this stuff and learning it, like you are reading these posts??

Ok, let's begin :-)
The basic rule of mold-making is a simple three-step process.
  1. Sculpt the original piece
  2. Make a mold of the original
  3. Cast duplicates of the original using the mold
That's it! ...Well, it does get a little more complicated than that. In fact, nothing will quite bend your mind like trying to figure out how to make a mold of something (it's like when you try to read words in a mirror and it's all backwards... Now imagine that in 3D).
In this case, I am sculpting the hands for our main character, Chris. To start, I need to sculpt the originals (step 1). For the armature (skeleton) I am just using some extra 19 gauge annealed steel wire. You can pretty much use whatever wire you want because it is not going to be animated.

Here I am wrapping little finger wires around the bigger wire. These wires are 28 gauge (I think... I lost the package) annealed wire:

The little buggers want to slide on the bigger wire and move all around on you, so I use a dot of hot glue to fix them where I want them:

Next I use the animator's best friend: epoxy putty. If you want a more detailed explanation of epoxy putty, check out my previous post "Christ Test Sculpt part 1". Basically this stuff becomes rock hard within a few minutes of catalyzing it.

Ah, now the fingers are secured in place with epoxy putty and trimmed down to length.I have made two hands, a left and a right.

I like having them bolted down solid so it is easier, MUCH easier to sculpt the clay onto the frame.
For this I am using Super Sculpey. I like it because I can bake it and solidify aaaall of those tiny little details without having to worry about bumping them and disturbing them.

All done! And now, into the oven. Super Sculpey bakes at 275° Fahrenheit and for these little hands I hardly even need them in there for 5 minutes.

I now have two baked hands, my original sculpts.
Now what? Well, we need to make a mold of them out of the Ultracal plaster (Step 2). You can pretty much make the structure for your mold out of anything (legos work great!) but I opt for a method my father invented. For about 50¢ at our local Home Depot we found nice wooden yardsticks that can be cut to length and hot glue gunned together. The beauty of this cheap method is they can be easily broken apart to get your mold out afterwards!

The hand is simply hot glue gunned to one side of the mold structure.

Here comes another great secret. When you pour the Ultracal over your piece, sometimes you get small air bubbles that end up ruining the mold. Have you ever noticed when you drop something into a glass of water, tiny air bubbles sometimes stick to whatever you dropped in the water? This is the same effect that is happening here. Even if you jiggle the piece, the bubbles don't always come off. Once you do get the bubbles off, however, you can even take the piece out of the water and drop it back in again and the bubbles don't come back. Weird, right? Ya, I don't really understand why it does that, but I know how to fix it :)

If you buy a rinse agent from your local grocery store (I use Jet Dry) and mix a SMALL amount in with a cup of water, you get what I have heard described as "wet water". Somehow the rinse agent makes water more likely to stick to the piece and not create those little bubbles. And just like with the water, once those bubbles are gone they won't come back, even if you take the piece out of the water and put it back in again. Again, if you know why this works, I'd love to hear from you!
Well this "wet water" will fill in all the small spaces on your original piece and create a track that the plaster will fill when you mix it in. Pretty ingenious, huh? No more bubbles!

So here's what you DIDN'T see. Right before I hot glue gunned the hand to the side of the mold, I dunked it in my "wet water" and made sure there weren't any bubbles on it, then quickly shook it off and glued it to the side of the mold structure.

Next step, build up half the mold with clay.
Since this is a two-part mold, you need to fill in one half with something else so the plaster only goes where I want it to go. I just used some extra Van Aken clay I had lying around. IMPORTANT: do NOT use any clay that has SULPHUR in it!! This is absolutely crucial and I will explain why later.

Notice the small beads I pushed into the clay. This is to help the two halves line up afterwards and it is also a critical step. You don't have to use beads, but use something to make sure they line up when you put the two halves together at the end!

Here is what the Ultracal 30 looks like:

It has the texture of very fine, powdery dust.

I weigh it on my scale (we don't need much for such tiny molds!)

The plaster is weighed to know how much water needs to be added. The Ultracal 30 needs to be mixed with 38 parts water to every 100 parts plaster. How did I learn this? It was on the box! haha

Unfortunately, I was unable to take pictures of the following process, but I will describe it using as descriptive words as I can. I poured the plaster onto the hand, filling the mold. That's it! Did I lose you?

Actually there are some important steps here, so read carefully. Once you mix and pour the plaster, jiggle the mold on the table for a minute or so to make sure we get all the little bubbles out.
Once the first half of the plaster has hardened, flip it over and pull out all the clay we put in underneath. DON'T TAKE THE HAND OUT YET. We need to paint some petroleum jelly (also known as Vaseline) onto the hardened plaster to make sure the 2nd half doesn't stick to the first. Then I mix up another batch and pour the second half into the mold structure.

Here is the finished mold:

Starting to make sense now, isn't it? Good because I'm going to take a quick detour.
This device is not necessary, but if you have the resources to make one it is incredibly helpful:

It is essentially a vibrating table for shaking your mold and getting all the bubbles out. Professionally these things can cost $150, but there is a much cheaper solution that you can make on your own to be found here:
We have now come to Step 3 and things are about to get a bit more complicated because I am going to introduce silicone in a moment. But first, I made another tiny armature for the hand, this one out of twisted 18 gauge aluminum wire (it is actually going to be animated). The fingers are the same 28 gauge annealed wire:

Because the silicone is going to be so thin over this armature, it will doubtless be quite translucent. The black epoxy putty will show through and look very weird. To counter this, I am painting the armature the color of Chris's flesh.

That's better.
OK, I am going to give you a quick crash course in silicone that is going to sum up A LOT of research and probably save you a ton of time researching this stuff. Go do your own research too though, there's a lot of info out there.

First things first: there are two major types of silicones we use. They are tin-cure and platinum-cure. More accurately, they are condensation-cure (tin) and addition-cure (platinum), but don't worry about that. Think of it this way: tin is a cheap metal that you don't really have to treat very special at all; it's not picky. Platinum is a valuable metal and you general take a lot of care with it if you have some; it's picky. Look at my shelf below:

See the four bottles on the left with the black caps? Those are tin-cure silicones. See the yellow and blue bottles? Those are Dragon Skin, which is a platinum-cure silicone. We are only going to focus on the Dragon Skin for right now. I use the other stuff for making flexible molds - basically I use it instead of the Ultracal 30 sometimes. Get it? (Note: the silicones could come in any sort of bottle, I am simply trying to provide a visual to help you differentiate the two. )

Dragon Skin!
Let me tell you the BIGGEST difference between these two types of silicones. Tin-cure are cool to work with, platinum-cure are a total pain in the butt. That sums it up nicely!

You must be very careful of what you have near the platinum-cure silicone or it will not "go off" and turn into a solid material. Here are some examples of things that will hinder the platinum-cure silicone: clays with sulphur in them, tin-based silicone (there's a sibling rivalry here), tin, ammonia, carbon monoxide, nitrogen oxide, amines, latex, and foam latex. This means NO latex gloves, NO sulpher based clay, and NO tin-based silicone anywhere near the workspace. Instead use vinyl gloves:
I spray each of my molds with Mann Ease Release 200 to make sure the mold comes out OK. This might not be necessary because silicone really only sticks to silicone, but I do it as a precautionary measure. Please let me know if you know otherwise.
(NOTE - I have read that only Ease Release 800 should be used due to the silicone oils in the other sprays, but have so far had no issues with Ease Release 200. Spray at your own risk!)

Here I am pouring out the silicone. You mix one part yellow bottle to one part blue bottle (A and B).
Another aspect of silicone is that it is crazy-ridiculous hard to paint, so it is much better to tint it by mixing color in before it hardens. And here comes another secret!
It is generally recommended to purchase expensive dry pigments to mix into the silicone to tint it. One of the dry pigments can cost up to $40 for one color!

I have found, however, that plain old acrylic paint gets the job done just as well IF YOU DON'T USE TOO MUCH. If you use too much, it WILL hinder the silicone (learned that the hard way). But if you are only using a few drops, you will save yourself a ton of money this way. As always, do some experimenting of your own first:

I used four drops of paint in this small batch of silicone. This paint was only around 50¢ a bottle!

This stuff has a real thick consistency that will surprise you if you're not expecting it. It is similar to taffy or very thick honey. I am mixing it with a popsicle stick (some of you may call it a tounge depressor, but to me they will always be popsicle sticks).

To make sure no bubbles show up on the surface, I am taking a paint brush and painting the Dragon Skin into the mold, making sure to get full coverage.

After painting both halves full, I put the armature into the mold and smack both halves together.

Normally I would wrap a rubber band around them, but I am all out of rubber bands and am using electrical tape instead. Can you believe it? I have all these exotic chemicals and no rubber bands...

And now we let it sit overnight.(you don't actually have to wait overnight. You can bake the silicone in an oven for about half an hour at 150° Farenheit and it will be ready to go, but it was getting late anyway...)


In the morning, I pop open the mold and viola!

We have ourselves a hand!

Immediately after popping the mold open, make sure to coat the silicone in baby powder. This makes it much easier to work with because the silicone wants to stick to itself unless you do.

It's a little difficult to see in the above photograph, but there is a thin skin of extra silicone all around the mold that we call flashing. It must be trimmed off, and this is a very tricky part of the job. I use a fine pair of scissors, like manicure scissors (you know, they type with the bent tip at the end). If you cut too little off, the edge looks jagged and it's hard to cut the remaining bit off. If you cut too much, you will cut into your piece and mess up the shape, basically ruining all your work. Be careful!

The finished product:

And there you have it, a silicone hand!!

As with most of these things, the first time isn't always the charm. This hand came out a bit lighter than I expected.... in fact, it looks dead. The guy is supposed to be pale, but that's a little extreme! I will have to experiment a few more times to get the appropriate shade.

So until next time, thanks for reading and keep checking back here for more exciting production stories!!


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