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Disclaimer: Researching the industrial production of silicone products is *very* difficult. The process of creating the substance is rather intense and science-y (technical term), but it also seems to be rather proprietary for each manufacturer. This article consists of conclusions I’ve drawn myself from textbooks, scientific journals, as well as peer-reviewed and industry publications. I’ve connected dots to the best of my ability, but I am aware that there may be places where I’ve come to the wrong conclusion with the information I was able to find. If that is the case, and you have better resources for me, PLEASE let me know by shooting an email to firstname.lastname@example.org.
Thanks to Stasher Bags and Food Huggers, we get questions about silicone almost every day in the shop, the most important of those questions: Is it safe to store food in? The short answer: Sometimes, at least according to the science we currently have. The long answer is below. I should also tell you now, if you’re about to jump to the bottom of the page, that silica, silicon, and silicone are distinct but related substances - and it’s definitely Silicon Valley, not Silicone. In case you were curious.
Silicone has been a household material in some form or another since the introduction of Silly Putty in the ‘50s. Did you think it was named for its goofy demeanor? Well, maybe that too, but also silicone! However, it’s a hard substance to nail down in the sense that the vast majority of the layman’s information about it on the web (so, like, not jargon-y and deeply scientific journal publications) is presented by companies who make and sell it. That always throws up red flags for me. Honestly, when I was first developing the spreadsheet of products I wanted to carry when Ware first opened, there was no silicone on the list. I just didn’t feel confident in the depth or reliability of the information I could find. And then I met Stasher Bags.
Stasher Bags caught my attention because they were the first reusable silicone product I came upon in the sustainable living world to so loudly proclaim that they were made of “medical-grade, platinum silicone.” This gave me a clearer starting place for my research, and in the years since I opened Ware, I’ve worked backwards from there. If you take nothing else from this blog, take this: If a product is not platinum silicone, you don’t want it around your food, your children, or your reproductive organs (I’m looking at you, menstrual cups and sex toys). I can’t promise something bad will happen if you do use lesser grade silicone, but I also can’t promise it won’t, so anything short of that standard won’t be found in Ware.
Let’s start with the basics and break down the question: what is silicone?
Silicon is an element you might recall from the Periodic Table. It’s the second most common element on Earth, second only to oxygen. However, silicon, the element, is so unstable that it doesn’t appear on its own in nature; it almost always appears attached to oxygen. The two together comprise more than 95% of the material on earth, and substances built of those two elements together as their base are collectively called silicates.
The only time you’re likely to come upon pure crystalline silicon metal (as it appears in the Table of Elements) is when it is produced in laboratory settings from silica. In this form, Si is an effective electrical semiconductor and is therefore a crucial component to just about all technology, from calculators to solar panels. The ubiquitous nature of silicon in computer chips is where the tech-capital Silicon Valley gets its nickname.
Still a rather generic term, “silicone” refers to polymerized silicon. The various formulas (or formuæ, for our grammar purists) for the rubbery material we recognize as silicone are also referred to as silicone elastomers, silicone rubbers, or siloxanes.
If you are more interested in the how-this-affects-my-life of it all, skip to the next section. In the event that we’ve got any true science nerds in the house (who happen to not already know how silicone is made), here’s how it goes down: Dimethyl Polysiloxanes are reinforced with fumed silica. The substance is then polymerized with either an acid or sodium hydroxide. At that point, you have a rubber we know as silicone. But you can further the process by vulcanizing the silicone with a variety of other elements in compounds. For the highest-quality, medical-grade silicone, the silicone is cured with platinum**. Hey, I warned you it was going to be a nerdy chunk of text.
That whole process produces a remarkably stable, rubbery substance. It far out-performs petroleum-based products in terms of heat, friction, and weather resistance. That’s why you find it in high-intensity environments like human body implants and gaskets on submarine doors. So why should anyone be worried about using silicone products in their personal lives?
Because “pure” silicone isn’t found in the open market as frequently as its name is. This is why I don’t typically trust silicone products when first presented to me. To cut costs, many manufacturers of the material will blend it with… drumroll… you guessed it - plastics, vinyl, and other petroleum derivatives. Bummerrrrrrr. Sometimes it’s just lower grade silicones, but still, that leads to a less stable substance. The fillers in lesser quality silicones tend to be the scary part, as they are never materials that are as robust as silicone, meaning they are more likely to leach chemicals into the things they come in contact with.
While the US’s FDA (and apparently Australia uses these guidelines, too) has regulatory standards for the grade of silicone it will give approval to, it includes silicones with approved copolymers like vinyl (that’s plastic).
When I’m not confident with US regulation around something, I often look to Europe and Canada to see what the standards are in those places that tend to be much stricter about both health and environmental regulation. In this case, Canada gives silicone the green light, and Germany does as well, both with stricter food grade expectations than the US (we’re not shocked).
As I’ve mentioned, you’ll find platinum-cured silicone is synonymous with medical-grade silicone in the US. For this designation, however, I was unable to find a certifying body. I have come across mention in every other possible format (including textbooks) that it is the highest quality silicone that can be produced, so the conclusion I’ve drawn is that the addition of the platinum curing is the best assurance we’re going to get from the government.
I’ll admit that my lack of clarity around this is likely due to the fact that all I have to fall back on is my deeply interdisciplinary (oxymoron?), science-based undergraduate degree and years of researching things for my own and professional curiosities. And while I think I’m pretty good at this most of the time, there are limits to the understanding I can have about a substance that I have neither the education nor resources to produce myself. That also means, though, that the average consumer is going to have a similarly frustrating experience, should they attempt to go down this rabbithole on their own. I don’t love that.
I’ve mentioned that we stick to platinum-cured, medical-grade silicone. Ware also only deals with silicone from businesses who have a tight handle on their supply chain. You may have seen the clear and blue, somewhat-jelly silicone lid replacements being sold by many green living businesses these days. You’re not going to find those in Ware. In all of the research I’ve done in sourcing those lids, I’ve boiled it down to one (maybe two) massive manufacturers in China (where all silicone comes from, that part isn’t the problem) who have countless certifications for the safety of their products, but not a single mention of platinum-curing. I’ve also never come across any information that speaks directly to those lids and their production process, just general certifications or certifications for other products.
It’s true that I could reach out to the suppliers and manufacturers on Alibaba (the source for most businesses selling these) and ask just that question. However, we make an effort to support more intentional supply chains and smaller businesses whenever we can. Not to mention we tend towards more substantial and durable items. All of that is why we carry Food Huggers and Stasher Bags. These are two companies producing their own designs, working directly with their manufacturers (or manufacturing themselves), and using exclusively platinum silicone. If we come across more brands with functional products at that production quality, we may grow our silicone collection, but it will always be with an abundance of caution (and research).
There are thousands of peer-reviewed articles supporting the stability and biocompatibility of platinum silicone in internal medical applications, specifically implants. Not only is the human body a harsh environment, it’s one that is easily affected by unstable materials (take BPA as it breaks apart from plastic, for example). Additionally, there was one study citing leaching of silicone in baby bottle nipples into milk. I imagine it is because of studies like these that silicone is not declared to be truly inert, at this stage.
I don’t say this with the implication that platinum silicone is outright toxic. I have immense faith in the fastidiousness of the scientific community at large, so I trust the initial findings of these studies are largely representative. However, I’m holding space for continued learning about a synthetic material that has only been subjected to human health scrutiny since the ‘70s and seen considerable change in their regulation still within the last 20 years. If the research is ongoing, that tells me there is more to learn. If information is difficult to obtain and processes are proprietary, it tells me the public has even more to learn, so I proceed with caution for now.
With all of that in mind and having reviewed as many studies as I have, I confidently stand behind the safety of platinum silicone for food storage and even menstrual cups. These are dramatically lighter loads than this type of silicone is developed to handle. But for any degree of decrease in quality of product from platinum-cured, medical grade silicone, I will pass on that product every time.
Generally speaking, I do count silicone as a rather clean substance, particularly compared to the alternative (in many cases). By contrast, plastics are known to be made with, “One hundred and forty four chemicals or chemical groups known to be hazardous to human health are actively used in plastics for functions varying from antimicrobial activity to colorants, flame retardants, solvents, UV-stabilizers, and plasticizers,” as published by The Endocrine Society in 2020. And that’s before we even get to talking about microplastics.
I’m sure it’s obvious to anyone who found their way to this page that silicone alternatives to disposable products are, at the very least, preferable insofar as they reduce the material sent to landfills. Menstrual cups as opposed to tampons and disposable pads are the first example that comes to mind, but there are also silicone baking mats that replace parchment paper and sleeves for glass water bottles that make clean-drinking water a possibility on the go.
We know that the petroleum necessary to produce the vast array of petroleum products we consume on this planet, from gasoline to every scrap of plastic or synthetic textile, is not only finite, but scarce - and increasingly so. Crystalline silica (quartz) sand is far more abundant, but still requires collection and transportation (transporting heavy sand requires considerable gas or coal). There are silica sand collection sites on every continent. I’ve learned that most silica sand is used in the country where it’s sourced, because it is the main ingredient in concrete, so it’s required in large quantities for construction. That particular grade of sand must be sourced from river beds, lake beds, and coasts, so it is actually doing considerable damage to environments the world over.
But I still can’t find a source on the internet (I spent weeks scouring Google and Google Scholar) that explicitly states where sand for silicone is mined. I’ve only come across silicone products made in China. Because they also mine and process a large percentage of the world’s
critical raw materials, it seems like a safe bet that’s where things are going down for silicone’s sourcing too.
To start, silicone is not biodegradable (hence its safety in medical applications) or recyclable - do not put silicone into your curbside recycling! There is an understanding in the world of recycling that the secondary material produced from the recycled materials compares in quality or application to the original product made from raw materials. In the case of silicone, there are only two options for end-of-life reapplications: the silicone can be effectively mulched for things like playgrounds and running tracks, or the silicone can be turned into silicone oil and used as a machine lubricant. Stasher Bag, specifically, has a partnership with Terracycle and will take back all of their products for the former application, at no cost to the consumer. Otherwise, silicone is less-than-exciting from a waste perspective - aside from the waste avoided by using some silicone products.
When silicone works, it really works well. But, like all materials, it has appropriate applications and inappropriate ones. Much like you wouldn’t use a wooden baking sheet, there are plenty of products made from silicone these days that just aren’t passing my sustainability tests, “zero-waste” swaps or otherwise, because it doesn’t make sense for that product to be silicone to begin with. Those products that come to mind for me initially are: cotton swabs, ice molds, toothbrushes/bristles, things you need rigidity, oven mitts… I could go on.
In some cases, the silicone alternatives simply don’t function like the original product. In others, I just don’t see the need to use a non-biodegradable product that we can’t recycle when there are other options. I’m particularly wary of the vast array of silicone bakeware in the world, not all of which has any evidence of being platinum-cured.
Silicone is significantly safer than petroleum-based plastics for its relative stability and structural integrity. I will continue to make the argument that silicone is a good solution, but possibly not a perfect one. As we are in the early stages of a societal shift away from plastics, I predict we will find increasingly better solutions to petroleum consumption, single-use packaging, and plastic in general. For now, I’m comfortable using the highest quality platinum-cured silicone for appropriate applications.
*Most of the technical understanding and breakdown of silicon etc. came from the textbook Chemistry of Elements by N. N. Greenwood , and A. Earnshaw (1997). Yes, I read a chapter of a college chemistry textbook to be sure I got this right.
** Reactive Polymers Fundamentals and Applications : A Concise Guide to Industrial Polymers by Johannes Karl Fink