I want to get into silicone casting, in particular to be able to make food-safe items out of (platinum-cure, obviously!) silicone. For various reasons (including simplicity/ease), I expect to be using primarily silicone-in-silicone. (Assume silicone-in-silicone for the purposes of this question.)

Now, silicone is supposed to be pretty inert stuff, but I was also watching this video that talked about urethane intrusion into a silicone mold.

Now, there's a bunch of incomplete information floating around, so I'm hoping to get something of a more definitive answer. What guidelines need to be followed to make a food-safe mold and/or part?

In other words, is it critical to stick to molds and/or positives that are already food safe, or is there a point at which merely using food-safe silicone can "sanitize" an unsafe surface? What materials (e.g. urethane?) do I need to keep far, far away from my molds to avoid contamination that would render them unsafe? Also, what steps if any do I need to take to keep the molds themselves safe after environmental exposure?


  • I'd like to follow (or at least be able to follow) the US FDA "small business" standards. Meaning, I'm not going to be paying for expensive certification, but should be able to show that the processes I'm following would be able to pass certification. I'm not actually planning on selling anything, but this feels like a comfortable standard for things that might affect my health or that of family and/or friends.
  • Final parts will be, at minimum, hand-washed before exposure to food and/or mouths. If necessary, I'm not aware of any reason I would not be able to boil, bleach, or bake them before use (provided that doesn't degrade the silicone, which I believe it shouldn't...).
  • Examples of stuff I want to be able to recreate might be sticks, bones, 3D prints of dubious provenance... really, anything that is assuredly not food-safe to start out.
  • Good follow-up question. This involves some specialized knowledge beyond crafting with silicone, so there may be limited readers on the site who can contribute good answers. Just an observation: the question seems on-topic for the site, but you will be betting your health on any answers you receive. The site has some very knowledgeable people, but if it were me, I'd want to go directly to the specialized sources for people who are trained and work in this area, rather than rely on the advice of strangers on the Internet, whose credentials you don't know. (cont'd)
    – fixer1234
    Aug 5, 2022 at 0:11
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    For whatever recommendations you get, it might be good to think of them as supplemental considerations, rather than rely on it as a comprehensive plan.
    – fixer1234
    Aug 5, 2022 at 0:11
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    Matthew, please take a look at Should questions asking how to craft something for a medical purpose or to meet health/safety requirements be on-topic?. I'd really welcome your input and thoughts.
    – fixer1234
    Aug 5, 2022 at 17:30
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    @fixer1234, even if this only gets answers in the vein of "how to get useful answers (for this specific question)", that's helpful. In my experience, it's incredibly hard to find such knowledge, or to even know where to look... and yet there are people that sell such things (example. Where do they get the information to do so?
    – Matthew
    Aug 5, 2022 at 18:57

1 Answer 1


Commercial food safe silicone items are commonly sold. This question assumes you can make these items at home to the same safety standard if you follow certain precautions (what those precautions are is the subject of the question). That is not a good starting premise. Some context:

Is silicone even dangerous?

Silicone is a family of substances, and silicone rubber also has additional substances in it. Some of the compounds are recognized as completely safe, others can cause damage when taken internally. (Further reading) For internal use (e.g., food/beverage, food contact, medical), the FDA has limits on the presence of the potentially harmful substances. Some silicone rubber is within the allowances once cured, and some requires additional processing to extract those substances (discussed below).

What does "food safe" mean, and can you make silicone items at home that are?

Commercial food safe items are "food safe" because they meet government requirements to be labeled as food safe. "Food safe", in this case, is a product claim, and in that usage, the term has a regulated meaning defined by the government.

Under the right conditions, you can produce silicone items at home, many or most of which would probably meet, or come reasonably close to, the requirements. But you can't do it reliably, or differentiate the items that do not. The risks depend heavily on the specific silicone you use.

The government requirements are covered within mountains of regulatory documents. They are readily available, and you can find summaries that will give you the gist of it. Those requirements generally cover the "what" for the results, not the "how".

The "how" is what you're supposed to bring to the table. The system is designed for manufacturers that will be selling the products to the public. The manufacturers are expected to know how to reliably meet the standards, and to have the expertise, equipment, and processes to accomplish it.

The question mentions "small business" standards, which I assume refers to the FDA Food Safety Modernization Act (FSMA). I'm not very familiar with the details, but my understanding of it is that it doesn't relax the relevant regulations. The regulations are to ensure public safety. You don't get to put the public at risk because you're a small player who can't afford to do everything properly.

You can save some cost by not getting products certified, which may be all you need if you aren't planning to sell them. But to be "food safe" as the term is defined, they still need to meet the requirements of the regulations, and you still need to bring the expertise and processes to meet the standards.

What do the "food safe" advertising terms mean?

You can buy silicone labeled as "non-toxic" and/or "food safe". Some manufacturers advertise that you can use it for food-related purposes, like making molds for food. Other manufacturers sell apparently similar non-toxic silicone and warn that it is not for making food molds or that use of the material doesn't guarantee that the result will be food safe. So what does the labeling "non-toxic", "food safe", or "use for food molds" really mean?

  • According to The Filtery (an interesting read),"Non-toxic" doesn't actually mean anything specific on a product claim. Dictionaries typically define it as "non-poisonous", which just means that if it harms you, it won't be via a chemical reaction. The term doesn't mean that it is non-harmful.

  • "Food safe" has a regulated meaning when used as a product claim (short summary). It refers to the finished product, not the raw materials used to make it. But to make a "food safe" product, you need to start with "food grade" materials.

    The silicone components should be "food grade" for this purpose, but don't qualify as "food-safe" because they are not the finished item. So advertising claims that the silicone is food safe aren't covered by the regulations and are meaningless, and intentionally misleading.

    Food safe is not a blanket term meaning it is or it isn't. It means safe for a specific type of usage under a specific range of conditions, like temperature, type of food, length of contact, etc.

  • Companies that advertise their silicone as usable to make molds for food, are implying things about safety that are misleading. Sure you can use it to make molds for food; you can use anything you want to make molds for food, so it's technically a true statement. Does the silicone meet FDA food safe standards when cured? You might want to ask the manufacturer that question (and pay attention to all the caveats).

Availability of "how-to" information

The question and comments refer to the problem of information being unavailable. The information is available, just not in the form you want. It is somewhat like getting information to safely remove your own appendix. The information for removing an appendix is found in medical textbooks; you would be hard pressed to find a tutorial for the casual hobbyist who wants to do it with stuff readily available at home.

The information on how to guarantee safety is geared toward industrial processes that can't typically be replicated at home. It tends to be technical, and in sources used by people in industrial and academic settings with the appropriate training.

A tutorial on making food-safe silicone stuff at home, if you can find it, can only focus on the normal process of handmaking silicone molds, with some common sense precautions. It can't cover how to reproduce the safety level possible in a manufacturing setting.

How do manufacturers produce food safe products, and how is that different from home?

Manufacturers start with food grade silicone (perhaps even essentially the same as some of the stuff available on the consumer market). They have equipment that can do precision measuring and extremely thorough mixing, and other production steps if needed, which often aren't done at home (e.g., degassing, post curing [see 1 and 2], etc.), and can tightly control the process to optimum conditions. They work with big batches, which minimizes inaccuracies.

They may do the casting by a different method than typically done at home (e.g., use of a press, or injection molding), that allows them to use clay-like silicone instead of liquid. Silicone that is closer to clay consistency has a number of benefits (e.g., ability to reliably mix thoroughly, not very sticky, less prone to pick up contaminants, no need for mold release, etc.). They are likely to use machined and polished original metal molds, rather than copying something, which provides a number of benefits besides lasting almost "forever" in production (e.g., easy to thoroughly clean and sanitize, no need for mold release, no exposure to cure inhibition, ability to control and monitor temperature, etc.).

They do trials with the silicone to verify its characteristics, optimize conditions, and establish measurement baselines. They do extensive testing on the materials and the results to ensure they are safe and meet all requirements.

If they could achieve the results simply by mixing and pouring the silicone, there wouldn't be much incentive to invest in all of the equipment and time for the rest of the process. And if the testing never failed, there would be an incentive to skip it.

Making the products at home would typically consist of using silicone labeled "food safe", with the mixing and pouring steps done by hand, and generally trying to be careful. It might include checking the result by sight and touch to see if it seems like a good cure.

If you start with the right silicone, most of the time, that could be close enough, and the results would be pretty safe. But it won't reliably replicate the quality and safety of the commercial product, and it carries risks that you have no way to assess.


  • If silicone is accurately, completely, and uniformly mixed, and cures properly and completely (which may take a long time without a post cure), it's pretty stable and inert. But if not, you could get the chemical components in your food. Even if they aren't poisonous, some of them aren't good for you (depends heavily on the specific silicone). Many things can result in incomplete cure (which may not be obvious): inaccurate mixing, cure inhibition, use of silicone past its shelf life, use of silicone that was stored or shipped under poor conditions, use of defective product, using the finished product before the cure is complete, etc. Use of silicone advertised as food safe doesn't guarantee that your finished item will be. Manufacturers that make this clear are being honest.

  • There are different types of potential harm. If there is an immediate, serious effect, that is at least good feedback that there's a problem. But you can also have problems resulting from cumulative exposure over a long time, and not be aware of it.

  • At least in the US, the regulations on food safe products apply to the supply chain and sellers (it's meant to protect the public). Individuals are free to put anything they want in their own bodies (and companies can sell you the silicone for your own use to do that). If you make your own items for use with food and end up harming yourself, it's all on you.

    If you give or sell those products to other people, or share food prepared with those products, you could become liable if someone else is harmed.

  • Say you use good silicone and do a good job of making the items, the result appears to be properly cured, you take proper precautions in using it, and only use it in approved ways. What's the likelihood of someone being harmed from it? Probably pretty low. Many people are buying the silicone and making food-related products at home, and they're not dropping like flies (at least not yet). But the risks are not zero, and manufacturers think it's cost-justified to spend a lot of money testing to avoid that risk.

    You might well be able to make items that turn out completely safe for the way you want to use them. But that isn't guaranteed. Making products at home is inherently less safe than the commercial products.

Precautions to take

Without the equipment, precision process control, and testing of a manufacturing setting, items made at home will be inherently less safe, and you won't know it. If you don't perform due diligence in selecting the silicone and do proper testing, you will be the guinea pig. There are no precautions you can take that will produce items at home that are reliably food safe as the term is defined. There are only precautions that can help minimize additional risks.

This list will get you started, but probably doesn't include everything you can do to reduce risk:

  • Figure out all the ways you might want to use the item, then make sure the silicone is rated for that.

  • The single most important precaution is starting with the right silicone. If you use silicone that cures to food safe, you've eliminated most of the risk that would not be apparent. Buy silicone that's advertised as "food grade" (or at least advertised as non-toxic and food safe and then investigate further). Stick with major manufacturers, and prefer a manufacturer that accurately represents the product (if they make misleading claims, it raises questions of how much you can trust their other claims). Ask the manufacturer if the cured silicone meets FDA food safe requirements without supplementary processing. Research the manufacturer for reputation for quality products, product recalls, regulatory action, lawsuits, etc. If you don't start with appropriate silicone, you can't get there from here.

  • Upon delivery and prior to each use, test a small batch to verify that it cures properly.

  • Don't use silicone past its use-by date, or silicone that doesn't cure perfectly or as fast as you expect. If it is still good enough for another purpose, use it for that, but not for a food-contact application.

  • As asked in the question, you are not limited to copying only items that are, themselves, food safe as long as you use an appropriate process. Since the possibilities are limitless, you would need to ask a new question about how to mold a specific item for a food safe result.

  • Do not incorporate anything that is not food safe (you can't make a food safe item by wrapping an unsafe item in a layer of silicone).

  • Familiarize yourself with what substances inhibit the cure of the type of silicone you're using and avoid them (brief summary, platinum cure specifically). Platinum cure can be inhibited by trace amounts of substances left by your gloves, tin catylized silicone, cleaning solutions, etc.

  • If a mold release is needed, use something food safe, or at least non-toxic and easily and completely cleanable.

  • Be meticulous in measuring, and using every bit of each silicone component you measure. Small batches will have bigger measuring inaccuracies.

  • Mix extremely thoroughly so the mixture is completely uniform.

  • Carefully inspect the finished items for anything that is not good, cured silicone. If the entire item does not look and feel perfect, don't use it with food. The risks aren't in the obvious rejects that you are aware not to use. They are in the ones that superficially look OK. You'll eliminate some of these by rejecting anything marginal or not uniformly good.

  • Use some method to objectively measure the cure and properties, even if it is just a durometer test and you compare hardness readings to a standard or baseline for that silicone when fully cured.

  • If the finished item has surface pocks from air bubbles, those will be hard to clean and will be prone to capturing contaminants. Consider not using it with food. Degassing the silicone in a vacuum chamber will minimize air bubbles.

  • Don't use the items for food contact immediately after demolding. The initial stage of cure is sufficient for demolding and handling, but the cure is not yet complete. If the product does not tell you how long full cure takes, give it at least a week before using it with food, or do a post cure.

  • Clean and sanitize the finished item before use. Use only methods and materials that are compatible with the silicone. Remove any surface residue, like mold release, then clean off any solvents or cleaning products used in that step. Bleaching or baking, as mentioned in the question, would be counter-productive as cleaning methods. Microorganisms are not the concern, and those methods would introduce something new to clean off, or bake on residue. Baking, at least at high temperatures, can also shorten the silicone's life (but baking at a moderate temperature may be warranted as a post cure).

    Bear in mind that no amount of surface cleaning will affect problems below the surface, and internal substances can migrate out or be exposed via damage or wear. Cleaning won't make it food safe if it is not already inherently food safe.

  • Don't use the items outside of the range of conditions the silicone is approved for.

Some of these precautions are more important for a silicone that requires a complete cure or post cure to be food safe. But you may not have the means to know for sure, so doing them can't hurt.

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