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I'm looking to get into silicone casting, and eventually I'm going to want to produce food safe products in custom colors. (Food containers, utensils... teething toys. Stuff that needs to be safe for both food contact and being repeatedly in my, or someone else's, mouth. Or in extended contact with other mucous membranes, in case I decide to be weird and make nose plugs. 😉)

Using already-colored product is not an option unless someone makes a color range of a single, food-grade product that would allow mixing to get custom colors. Although, I want to eventually be able to do metallic and/or glow-in-the-dark colors as well.

I don't need specific product recommendations, just general info, e.g. are alcohol-based food-safe dyes okay? Mica powder? Basically, what do I need to be looking for in order to find a suitable product?

...and of course, it needs to be a product that doesn't prevent curing or otherwise cause the silicone to no longer be food safe. (Obviously we're talking about platinum-cure.)

I know this is possible; there are plenty of colored silicone products in existence, in far too many colors to believe it isn't possible to create custom colors. For example:

Images courtesy Amazon

And here's an example of glowing colors: https://www.amazon.com/dp/B07F2NNM3Q.

However, it seems almost impossible to find information on how this is accomplished.

p.s. Yes, I'm aware that legally speaking I would need to get my products certified. Even so, surely there are products known to be capable of achieving certification, just as I'm sure there are others known to be harmful.

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You're kind of asking the wrong question. How to color food-safe silicone is the simple part. You just add food-safe colorants. There are companies that sell these, like Colorsoul, a Chinese company, sells LSR liquid silicone colorants, some of which are food safe silicone additives when properly used.

The hard part is in the definition of food-safe or other kinds of "safe". It isn't food-safe because you make it from components that are food safe. It's food safe because you convince the appropriate government regulatory organization that your finished product meets their requirements for being labelled as safe for a specific purpose.

There are different kinds and levels of "safe", with different requirements. For example, medical devices, infant bottle nipples or teething toys, food storage for various types of foods and storage conditions, temporary food contact, high-temperature cooking utensils, etc. It can be expensive to meet these regulatory hurdles (and even more expensive if you don't).

Also, a "food-safe" (or other kind of "safe"), label applies only to the specific type of use you get it approved for. So you couldn't get approval for a utensil that will be in temporary contact with food, and then make nose plugs out of the same material and claim they're safe for that purpose.

Making something that you can claim or imply is food-safe, and sell legally and with limited liability, generally isn't within the financial means of a hobbyist occasionally making them in their basement. It requires a substantial investment that would normally be amortized over a lot of production on a commercial scale. And the colorants are sold in quantities appropriate to that scale.

To better address the clarification added to the question and discussed in comments:

If you will be making these items just for use by yourself and your family and friends, won't be selling them, and they don't pose a clear and present danger to the public, the government won't come after you, and your friends probably won't sue you if they get sick and understood the risks. People are free to put anything they want into their mouth and other orifices (nose and ears are some examples of other orifices).

So you can use any basis you want to define a level of safety you're comfortable with. Say it will be adequate to just restrict the materials to substances that have been certified as usable in food-safe end products, and you will judge proper curing by the physical characteristics of the finished item (does it feel properly cured, no odor, no surface residue, etc.). Just use colorants that are sold for use in food-safe products.

The LSR, mentioned earlier, is one. But you could also contact other big makers of "food-safe" silicone or colorants, like Smooth-On, to inquire about which of their products might be suitable. Making products sold as food-safe is normally done on a commercial scale because of the costs involved; that's the audience and market for the colorants. So sellers of the colorants don't advertise them to the public or sell them in small retail quantities for hobbyist use.

You could also use pigments that aren't harmful and may be more readily available. For example, colored mica is used in things like eye shadow, which needs to be safe enough that people won't be seriously harmed by accidentally getting some in their eye or ingesting a small amount. It takes very little of it to color silicone, it gets permanently contained within the silicone, and nothing leaches out of it when exposed to water or substances in food.

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  • There's also a distinction between "compliant" and "approved". The supplies you buy are generally labelled as having been tested to comply with the regulatory requirements, but using them doesn't mean your result is approved. For example, see this link regarding Smooth-on food-safe silicone.
    – fixer1234
    Aug 1 at 6:50
  • So, are you saying if I want to make stuff for my own, personal use (well, "friends and family" anyway), it's not economically feasible? Even if I'm expecting to go through several gallons of silicone (not all the same color)?
    – Matthew
    Aug 1 at 13:59
  • @Matthew, nobody can stop you or your family or friends from putting whatever you want in your mouth, and if someone gets sick from it, the government won't come after you and you probably wouldn't be sued. There are lots of colorants you could use that aren't particularly good for you, but aren't poisonous or harmful in tiny quantities. You could probably use colored mica (like from dollar store eye shadow). You can get silicone colorants in small quantities on Amazon that don't claim to be food safe, but a tiny amount within cured silicone may not pose a significant risk. (cont'd)
    – fixer1234
    Aug 1 at 17:16
  • The biggest problem is not having the means to test and verify a perfect cure, with no chemicals leaching out. That's different from it feeling solid and with no surface residue. A functional but imperfect cure isn't an issue until you put it in your mouth or store food in it. Even an imperfect cure might not make you sick from limited exposure. What was Clint Eastwoods line, "Do you feel lucky?"
    – fixer1234
    Aug 1 at 17:16
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    @Matthew, then just stick with colorants that are sold for use in food-safe products, like the LSR. Making food-safe (or other-safe), items is a specialty that's normally done on a commercial scale because of what it entails. So you might have a hard time finding colorants labelled as safe for this purpose at hobby stores, or even Amazon. It would take a little research and maybe contacting some manufacturers about what might be suitable. Actually, companies that sell the stuff in commercial quantities might sell you a collection of small samples of primary colors (that can be mixed), (cont'd)
    – fixer1234
    Aug 2 at 19:18

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