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Making Body Parts and Monsters out of Fiberglass

Ever wonder how they made the costumes for Darth Vader and the Storm Troopers in Star Wars? Basically they did it the same way car bodies are made… in a mold with fiberglass, or a similar resin. In fact, so many things are made with plastics and resins today that it’s not likely you have any device that doesn’t have a molded part on it. I have seen some really complicated, and convincing, costumes made entirely from molded fiberglass, including whole suits of armor!

With the basic knowledge of how to do this, you can make almost anything you’d like. Below I will describe how to make a simple body part, but these concepts can be extended to almost any level to make extravagant costumes, monsters or even sets (think of the Jet in the opening scene of Mission Impossible II. That was made as a fiberglass model a bit larger than a minivan).

For this project I have decided to make a body part, a hand. Not just any hand, but a mummy hand. I also chose materials that you can buy locally:

  • plaster of Paris which you can buy at any hardware store
  • cheese cloth which you can get anywhere cloth is sold, or where canning supplies are sold (Walmart carries it in their fabric section)
  • fiberglass resin and fiberglass cloth or spun fiberglass, which you can get at an auto supply store
  • plastic cups and spoons, and cheap (a.k.a. disposable) “chip” brushes

The Mold

I wanted my body part to look like a mummy’s hand, so I needed to make a mold that would give it mottled skin. I could have taken modeling clay and sculpted the part that I wanted, which is how most parts start, but I decided to use my own hand and arm, since I’m not so good at sculpting.

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I mixed up some plaster of Paris as per instructions, and dipped strips of cheese cloth in it. I then coated my arm with Vaseline petroleum jelly so the plaster wouldn’t stick, and then layered the plaster infused cheese cloth onto my arm.

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I pushed the cheese cloth into the spaces between my fingers, but made sure I had no convolutions (where the mold folds under itself – when you try to take the finished product out, you will have to break the mold in order to get it out – bad if you want to make another, identical part). I let the cheese cloth hang over the end of my fingers to make sure I covered the tips of my fingers.

I used a canned vegetable can to rest my hand on so it would have the right bend to it. I made sure I had a tall cup of coffee, good music on, and then I waited the requisite time of about 45 minutes for the plaster to harden, trying not to move my hand or arm during that time.

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After hardening, I carefully pulled the “cast” off (Ouch! Not enough Vaseline, too many arm hairs), pushing and pulling at my skin to get it to break away from the mold.

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Casting the Fiberglass hand

I coated the inside of the mold with Vaseline to keep the resin from sticking to the mold. Unfortunately, one of the problems with plaster is that it is porous, and it takes a lot of Vaseline. I did have some trouble getting the resin hand out of the mold, ultimately breaking the mold. There are commercial anti-stick materials that work really well, which I’ll tell you more about later.

I wanted the skin to have a mottled look to it, so I made up a small amount (about two ounces – see below on how to do this) of resin and coated the inside of the mold, not getting rid of any air bubbles (that helps create the mottled look) and let that harden before making the main cast.

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Next I cut a piece of fiberglass mat material to fit inside the mold. I also pulled some individual fibers out to fit into where the fingers are.

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I then mixed up about 8 ounces of the resin with the hardener as instructed on the can of resin, and stirred it. Then I poured the resin into the mold.

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…and spread it out with a chip brush.

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I let this harden for about 2 hours, and then began pulling the mold from the “hand”:

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This, it turns out, was not so easy. The Vaseline had been absorbed into the plaster, and the resin was stuck in many places on the mold. I ultimately destroyed the mold getting the hand out. That’s ok; I can always make another one. Great way to sit and pity the folks with broken arms set in casts…

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Painting Your Body Part

I trimmed this with a jig saw and with “nippers” to cut away the excess, and then painted the hand using acrylic paints (modeling paints would have been better, but this is what I had on hand). I painted it with yellow ochre:

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After drying, the molting looks like a mummy’s hand:

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I added some red and black paint to make a “wound”:

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…and did the same for the fingers:

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…and, viola, a mummy’s hand!

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Going Further With Your Newly Acquired Casting Skills

This ain’t nothin’, folks. The sky’s the limit, literally. There are airplane kits you can buy to build a whole airplane out of fiberglass! But that’s a different article. Let’s stick to costumes, sets, body parts, weapons… and the list goes on.

I said above that there are better materials out there. You betcha… there is a company that specializes in moldings and castings called Smooth-on, and you can visit their web site at http://www.smooth-on.com/

They have every material imaginable for making molds for casting, anti-stick material, casting resins, silicon rubber (like for a mask), etc. They have training videos you can watch, and videos that introduce each of their materials. Even Martha Stewart has a video on this web site!

There are also hundreds of “How To” videos on YouTube that will lead you step by step in molding and casting. When you become the resident expert, then make your own video and post it on YouTube…

Ok, now, get started on that seven foot monster, and Happy Haunting!


About David Lay

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2 comments

  1. I am going to attempt my first pay-to-enter haunted house this year.I need some thrifty ideas to really scare patrons without me fainting over the cost.Help!!!!!!

  2. Wow! I think that this is really cool and fun to do. I would definitely try it out! 🙂

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