Casting in "Metallic" Silicone

[Twi'lek Pam]

This tutorial will show the steps I used to create flexible "metallic" bracers for my Twi'lek costume. The steps can be used for many types of projects.... just use your imagination!

 

When I first set out to make a pair of bracers for my Twi'lek costume, I thought about creating them out of solid material, such as styrene. The problem, though, was that nothing would stretch enough to let me slip them on, and then close tightly again to be form-fitting on my wrists. I finally decided to make the bracers out of flexible material. I originally cast them in latex, which worked well.... for just one event. Latex tends to dry out, crack, and stiffen with time, and the next time I wanted to use the latex bracers, I found that they weren't in very good shape anymore. So, I decided to cast them again in platinum cure silicone, which is far more durable and far more flexible than latex. These new bracers will last for years!

 

A word of caution: Silicone is terrific stuff to work with, but most paints and most glues just won't stick to it. They'll peel off as they dry. If you choose to cast costume pieces in silicone, be aware that you will need to purchase pigments and adhesives that will bond to it. I like to use Smooth-On products. You can find everything you need right there on one website, and you'll know exactly what is compatible!

 

 

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I started out by using a piece of thick paper to decide on the size and shape of the bracers. I wrapped it around my wrist and trimmed it until I got a shape that I was happy with. (Yes, I made it asymetrical on purpose!) Be sure to use thick paper, not thin, to help mimic the bulk of cast materials. Once I had cut the paper to the correct size, I set it aside to use as a template.

 

Then, I used a rolling pin to flatten a ball of oil clay to a 4mm thickness on an old cookie sheet. Cookies sheets are great for sculpting on. They're sturdy, transportable, easy to clean, you can work with the tray on your lap, and if the clay sculpture needs a quick warm-up or cool-down, you can shove the tray in the oven or fridge with no problems at all!

 

Once I had the clay flattened, I used the paper template to cut it to the correct size and shape. Then, I used a variety of tools to create the designs. In addition to sculpting tools, I also cut up some stamps (the kind used for decorating cards and scrapbooks) and used them to create the swirl patterns. The stamps were small, but I was able to match up the patterns closely enough that the designs seem continual across the bracers. The domes were made with half-beads pressed into the clay, and the borders were made with a cheap little clay extruder I purchased from Michaels.

 

 

 

 

When the sculpture was finished, I gave both the sculpt and the surrounding tray a light coating of Crystal Clear spray paint, and then let the paint dry overnight. The Crystal Clear creates a protective barrier which helps the mold release from the clay, but you have to give it plenty of time to dry before moving on to the next step!

 

The following day, I used a strip of thick paper to create a low retaining wall around the sculpture. I used bits of water based clay to seal the wall to the cookie tray, and then I mixed up a small batch of Ultracal. Ultracal is stronger and far more durable than plaster, and MUCH better for mold making! Always pour the mold material BESIDE your sculpture, and let it flow up and over the sculpture on it's own. This will allow the mold material to push air out of its way as it spreads, preventing air bubbles from being trapped in the mold. I let the Ultracal sit overnight, and then flexed the cookie tray to make the rigid mold pop right off. Ultracal sets quickly and could have been removed faster, but giving it plenty of time to cure before handling is always better. The longer it sits, the stronger it becomes, and patiently giving it a bit of extra time prevents damaging the mold with chips or scratches that can be caused by handling it too soon.

 

 

 

 

Silicone will not stick to the Ultracal (unless it was mixed to be very porous), but it is always wise to give any mold a light coating of release before casting something in it. Doing so lengthens the lifespan of the mold, makes demolding considerably easier, and often gives a better surface to the cast pieces. Be sure to use a mold release that was created for the type of silicone that you are using!

 

For my bracers, I mixed up a batch of Dragon Skin. This is by far my favorite kind of platinum cure silicone! Before pouring the silicone into my mold, I added a very small amount of the metallic gold powder that is typically used for cold-casting with resin. There are a number of sources for cold cast powders, but I like to use Alumilite. (I had experimented first with small batches of Dragon Skin and Alumilite to make sure that the powder would mix in properly, and to make sure that it wouldn't inhibit the cure of the silicone. To my delight, it worked perfectly!)

 

For the bracers, I mixed the Alumilite directly into the Dragon Skin. I also experimented with mixing the powder into Psycho Paint, and found that it worked perfectly there as well. Psycho Paint is a silicone base created for pigmenting silicone castings. You mix colors into it, and then paint it on with a brush or airbrush (if properly thinned.) This told me that I would be able to paint in metallic weathering or highlights with different metallic powders if I wanted to. Since the powders can be dry brushed into a mold before casting, I also could have brushed in some highlights with another color of powder before pouring in the gold-tinted silicone.

 

 

 

 

The back side of the bracers have beautiful swirl lines and bubbles (since I don't have a pressure pot for casting). Neither the swirls nor the bubbles show up on the front of the bracers, though, so it's not a problem.

 

 

 

 

 

This is how the bracers looked when they came out of the mold. They're wonderfully metallic.... and they're flexible enough to easily wrap around my wrists! I used silicone glue to permanently attach fuzzy sided velcro on the back of each piece, and then I used a piece of the hook sided velcro to secure them on my wrists. They're completely size-adjustable, and quite comfortable.

 

 

 

 

 

 

 

 

Pam

[Guest Anonymous]

Outstanding Pam!

 

Casting is the next skill I plan to work on and you answered several of my questions right off the bat! Thanx!

[Guest Anonymous]

Those look very nice.

 

I've read that one can paint in areas using different color silicone then pour the main color over that before it sets to get different colors in the finished piece, though I haven't tried it myself.

 

I've also read that all kinds of things can inhibit platinum from curing so it's more difficult to work with than tin based silicon, which cures from moisture.

[Drago Lordist]

sweet tutorial! good work as always pam!

[Guest Anonymous]

This is far less frightening to me that working with plastics. Do you think this would be an acceptable way to make Guri's gold shin guards? Also, do you remember a general ratio for the metallic powder to silicone that you mixed up?

 

Thanks, Liz

[Twi'lek Pam]

This is far less frightening to me that working with plastics. Do you think this would be an acceptable way to make Guri's gold shin guards? Also, do you remember a general ratio for the metallic powder to silicone that you mixed up?

 

Thanks, Liz

 

It might take a bit of experimenting to get the right look and to figure out how to close the guards strongly enough to take the wear-and-tear of leg pieces, but I imagine silicone could be used for that project. (I've tried this technique to make thigh armor pieces, and I found that it broke free of the silicone glue within ten minutes of walking. Leg pieces have to endure a lot more than wrist decorations do!) I don't think metallic powder would be the right thing to use, though. The shin guards are meant to match the color of her bodysuit, which is yellow rather than gold. You can tint the silicone with silicone colorant or oil paints, though.

 

Pam