Gem Clusters: Know Your Silicone!

by Ilea Wakelin

The face painting world has caught the build some bling bug! This has led to tutorials, and videos showing how to make gem clusters to add to your face painting designs, but it also has created some rather lengthy discussions on which type of silicone is the best, and safest for the job.

There indeed is a lot of talk about silicone, and even a few claims going around that all silicone is the same. It’s not. In this article I will give you my thoughts as a professional special FX makeup artist who has been working with silicone for a few years now.

Ok! So lets get detailed. First of all, a disclaimer: I’m not a scientist, I can barely even bake a cake properly while using instant cake mix (though somehow I can cast foam latex with little trouble…..). What I’m trying to say is that I’m not an expert by any means, all the information below is from a formal study from makeup school, personal study at home, and working with others in the FX industry in Vancouver. If you have any doubts or questions about the silicone product you are using, then it’s best to consult the MSDS for that product, or write to the company or a distributor for more information. I repeat, I’m not a scientist.

Glad we got that out of the way.


What is silicone?

In a nut shell, silicone is a synthetic polymer, which vulcanizes (sets), at room temperature, into a rubber like material. These types are known as RTV Silicone (there are other types, but that’s another can of worms). It comes in soft and hard formulations, it is inert once cured, flexible, and heat resistant. RTV silicone rubber is what we use in the movie, entertainment and special effects industry. The softer “skin” like silicone rubber is what is most used by make-up and FX artists, and were developed specifically for sfx makeup artists. Certain kinds of this silicone are also used in the medical prosthetics industry, as well as the…. not-so-medical prosthetics industry. It can also be used as a lubricant in it’s uncured form; which is apparent to anyone who has ever spilled uncured silicone on their living room floor.

Results may vary.

So to start there are 3 basic types of RTV silicone. The first 2 are what are known as two-part silicones, These include a part A and part B which need to be measured and mixed together right before use.

1. Platinum Curing (Addition) Silicone

This is the more expensive type of silicone for many reasons. First off they are extremely pure and when used for mold making can produce the most detailed  molds that last pretty much forever if you take care of them. This is one of the reasons this is a go to product for those in the FX industry. This type of silicone are also used for   theatrical and medical prosthetics, for medical equipment, candy molds, cookware, and nipples for baby bottles among other things. They are safe for use on skin when cured, which is why this silicone is used for FX work where the appliance comes in contact with the skin. Unfortunately, platinum curing silicones are also the touchiest of the silicones to work with. Their cure can be hindered and contaminated by moisture, sulfur, latex, tin, bad hairstyles or even looking at it the wrong way.


Even though it’s hard to work with, it’s the only one on this list that has had extensive dermatological testing.

2. Tin Cure (Condensation) Silicone

These are most commonly used as a mold making material for art, like making props, or molds for sculptures and other industries. This type of silicone is NOT approved for long term contact with the skin, bake ware or any other food contact, although some are used in making seals for potable water supplies (*raises an eye brow*…). They also don’t last as long or capture the most detail when making FX molds IMO, but they aren’t bad. Once cured they can last about several years. They are still a very stable and safe material for a wide variety of applications though. They can even cure underwater and actually need some moisture in their chemical process when curing. There is very little that will inhibit the cure of a Tin condensation silicone actually. But if you are thinking of using it for gem clusters, think again. This one is the most likely on this list to cause a bad reaction if you have sensitive skin, as this compound was not made to be used cosmetically with prolonged skin contact. So don’t use this kind.


3. One-part, (Self Curing) Silicone

These are the most common ones, that are used as caulking and aquarium sealants. They are a variant of tin cure and are usually sold in air-tight tubes of some kind. This type of silicone is further divided into 2 basic subclasses based on the catalyst they contain

a) Acetoxy – these are the common ones you will find at your home reno centers, and hardware stores. They typically have a strong vinegar (acetic acid) smell during their curing process. These are to be avoided if you are looking at a application that involves use on skin at any time before or after curing.

b) Oxime – are commonly referred to as odorless curing silicones and can some times be found in some building supply stores or craft and hobby stores but are usually more expensive. If you are going to use this type of silicone for making gem clusters, there are some things you would consider.

Image: Bill Nye The Science Guy
Image: Bill Nye The Science Guy


If one thing so far is certain it’s that not all silicone is created equal. Even if you have an Oxime silicone, it may contain methylpolysiloxanes which are known to generate formaldehyde (a skin, eye, and throat irritant.), but only upon exposure above 300 degrees centigrade in atmospheres that contain oxygen. Might be a problem in the FX industry depending on what you want to use it for, but I think I can safely say that that’s not much of a worry for face painting purposes, so I digress.

Avoid silicones with antibacterial and fungicidal additives, as they may put your skin at risk. I also I find it’s best to avoid silicones with phthalates, which is an additive to plastics to increase their flexibility, transparency, durability, and longevity etc.  Low-molecular-weight phthalates such as DEP, DBP, BBzP may be dermally absorbed, though studies on the effects of this are still on going.

However,even with out any of those additives, some brands of oxime silicone may still cause a mild skin irritation. But the chances are extremely low if you use it after curing as the compound itself is essentially innate once cured. Silicone itself once cured has an extremely low occurrence of allergenic skin reaction, it’s the additives you have to pay attention to here. Even with out all those additives, will cured Oxime silicone cause irritation to the skin? Very unlikely, but I have been unable to find any sort of definitive answer on the subject.

Image: Futurama
Image: Futurama

Personally if I’m going to use a one part silicone for making gem clusters then I look for a silicone that says “AQUARIUM SAFE” on the package, as these are the least likely of the one-part brands of silicone to leech anything after they are fully cured.  While skin irritation is least likely with aquarium safe silicone over all, it’s still a very small possibility which usually happens if the product was not allowed enough time to fully cure before use. This is why I always wait at least 24 hours before using any gem clusters I made. Basically this stuff is good to go in water for over the course of years of close contact with a with biodiversity of plants, fish, and all kinds of reptiles etc. People trust this stuff with their rare exotic fish that are worth more then your house, so I think you’re in the clear with this one. If  (and that’s a big if) a reaction were to occur, it would probably be, at worst, a red mark that’s a little itchy for a day or two… if that.

However, something to note is that if a reaction does occur, and some one does happen to sue you over a small red itchy spot, your insurance probably won’t cover you because technically you were using a product for something other then it’s intended purpose. Though given all that I know about silicone the chances of that happening might as well be like winning the lottery twice. Once for some one having an extremely rare reaction, and again for that same someone wanting to sue you over a small itchy spot. I think it’s a safe bet that the odds are pretty low.

As an FX artist by trade I just so happen to have more of my medical grade silicone in the house on hand at any given time, so I usually find myself using both just as often. Knowing what I know about silicone I find it overall to be an extremely low risk product that is easy to find, and easy to work with for making gem clusters to apply to my designs.
Awesome 404 of awesomeness

At the end of the day, you are doing your best job by knowing the answers the questions before they are asked. If you are questioning what silicone works best take some time to do a little research. Building bling is not only fun, its really adding the creativity factor back into our artwork. So once you have the info and back ground on supplies you can use your time more wisely to bling the world!

Thank you for reading, I hope this helped!

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