I'm thinking about retiring it. Why? Friend, you don't give your name, and I feel like I don't trust you. It's not just your mustache. I feel like you know more about silicone than you're letting on. Because what you have asked is just too good of a question. I feel like you have to have known what a ridiculously rich topic this is, and you were just setting me up for success by lobbing me that giant softball.
You had to know that I could spend whole hour talking about what silicone is and why I increasingly dislike it in the kitchen. In which case, I thank you. And if I'm wrong and you're sincerely ignorant about silicone, all the better, because I'm here to give you the goods on silicone. And it's not some big scandal. I'm not here to get clicks by fear mongering. Silicone cookware is fine. Every kind of cookware has its pros and cons. But I was just thinking that I'm about done with silicone tools in my kitchen.
Even my beloved blue silicone spatula that I've used because it looks great on camera — I find myself reaching for this less and less. I reach for my broad wooden spoon instead, because I think wooden spoons are the perfect cooking spoons. I could talk for a whole hour as to why, and, knowing me, I probably will at some point. I'm feeling done with silicone because silicone retains odors. It gets stinky, for reasons we'll get to. And it will transfer those smells to the foods you're working with, particularly fatty foods, which tend to absorb and retain odors. So when I use my favorite blue silicone spatula to scrape something both fatty and mildly flavored out of a bowl, like whipped cream, the whipped cream ends up tasting a little like the dishwasher, because the silicone picked up the smell of the dishwasher — which is, at least, a clean smell. I mean, it's not clean.
Clean just means free of any undesirable matter. I do not desire detergent fragrances in my food, but at least it's an odor I associate with cleanliness because I use soap to remove other undesirable things, therefore in my mind soap is "clean" even when it literally is not. Silicone can absorb far more offensive odors, however, as it did when Lauren cooked some stuff like a month ago, and she cooked more than she would actually eat, which she always does because she follows recipes too literally, and she packed up the leftovers, which she always does even though she knows damn well she's not going to eat them because she has a thing about eating leftovers.
She doesn't want to feel guilty about throwing the leftovers away, so she outsources that emotional and physical labor to me, her dear husband. After the leftovers have done their monthlong probationary period in the fridge, I finally relent and take them out and throw them away, and that's fine. If Lauren were here she could tell you about one of the many annoying things that I do, and she'd be right about it. And even she was wrong about it, there's still probably another thing I do that she actually deserves to be frustrated about, so I can just consider the fake thing she's complaining about to a be a proxy for the real thing I do that's bad, and right there is a marriage pro-tip for you kids out there. Anyway, on this occasion, Lauren had boxed up her doomed leftovers in the one-quart cylindrical, sealable glass containers that I normally age my pizza dough in, and everybody on the internet asks where I got those and the answer is I just got them from the little cookware section they have in every grocery store and no I don't remember which grocery store it was, but they're made by a glassware company called Anchor, and they came with silicone lids.
You can't make a resealable container out of only glass because glass isn't soft and stretchy. You can't stretch glass around an opening, at least not at normal kitchen temperatures. I mean if your kitchen is 700ºC, that's your business.
But these containers have silicone lids, and because the lids were in contact with Lauren's gross leftovers as they molded in the fridge for a month, the lids now smell disgusting, because silicone absorbs odors for reasons we'll get to. I washed everything by hand real well and then I put everything in the dishwasher and ran it and the next day the silicone lids still smelled really bad and they had transferred that smell to everything else in the dishwasher. Those lids are currently soaking in my sink in a 50/50 mixture of water and white distilled vinegar to deodorize them, while I'm running that whole load of dishes over again to get rid of the smell. I am feeling like I am done with silicone in my kitchen, even though I'm probably not, because silicone is probably the best option available for certain things, even though it sucks.
What even is silicone, our mysterious mustachioed questioner asked. He said, "I know it's an element on the periodic table," and he was wrong about that. Silicone is not a chemical element. Silicon is. Silicon is an element, silicone is not. The difference is the silent "e" at the end of silicone that tells you to make a long "O" sound instead of a short one. Silicone. There's four irritatingly similar-sounding and similar-looking words we need to untangle — silicon, silicone, silica and silicate — those are four different things.
Silicon, with no silent e at the end, is a chemical element on the periodic table, #14. It is a metalloid, meaning it's kinda like a metal but also kinda not. If you google image search "pure silicon," it literally looks "metalloid." It's silver and shiny, like a metal, but it's brittle, so it breaks and flakes like a rock. We were talking about anthracite coal last week — pure silicon looks like silver anthracite. I suppose that shouldn't surprise me, given that anthracite is almost pure carbon, and carbon is also a metalloid, or at least some people consider it a metalloid. There is no set definition of a metalloid — it's just a substance that exhibits some of the characteristics of metal but not all of them, and "metal" doesn't even have a totally stable definition. It's a cloud of characteristics or properties shared by certain substances at common temperatures and pressures. It's thought that every element will become a metal at a high enough pressure.
As a result, what astrophysicists call a "metal" is totally different from what other scientists call a metal. Carbon and nitrogen and oxygen are all metals when you're looking at them in a stellar core. It's really just helium and hydrogen, the super-light elements at the top of the table, that are NOT metals in your typical astrophysical contexts. Everything else is a metal. Context is everything. Context is for kings. We do not live inside stellar cores. In the kinds of conditions where we live, metals are elements like iron, copper, tin — and mixtures of elements that still yield metallic substances are also called metals, like bronze — copper mixed with a little tin or arsenic.
It doesn't have to be one, pure element to be a metal. If you take any substance, and you polish it or fracture it or melt it down and then pour it into a mold and make a block of it fresh, it is considered a metal if, under the aforementioned conditions, it is shiny and it conducts heat and electricity particularly well. Both of those properties have the same cause, which is free electrons. The electrons in metals are not all bound up with a single atom or in a covalent bond between atoms. The electrons can move around which is what makes metals so electrically conductive, and it's also what makes metals shiny.
That i couldn't even begin to explain.
Another cause of shininess, or "luster" is the technical term, is smoothness.
A material has to be very smooth to reflect a ton of light very directly, which is what a shine is. If the surface of a material is rough, light goes in there and it bounces around between all the imperfections in the surface like a pinball in a machine, and the light bounces back out again in a million different directions, and its power is dispersed in a million different directions — a million different tiny light beams that don't amount to much.
If you polish a material until smooth, that simply doesn't happen. The light hits the surface and bounces straight back out again, in a concentrated, highly directional beam. And if you're standing at the correct angle, that light will bounce directly into your eye and you will perceive it as a shine — a much brighter beam of light coming off the object compared to all of the far less direct and/or less intense reflections that make the rest of the object visible to you. If you can see it, then some light is reflecting off of it, but not nearly as much as on the part of the object that is white with shine. Not everything that is shiny is a metal. Water can be kinda shiny, even though it is not a metal, because it does not have free electrons.
As a result, pure water does not conduct electricity. It's an insulator. The reason why you would nonetheless die if you dropped a toaster into the bathtub with you is that your bathwater isn't pure. Basically no water is pure. It's got all kinds dissolved stuff in it, like minerals that can conduct electricity — electrolytes! That's why we need electrolytes in our body fluids to convey electrical signals — and even then water is still not a great conductor. It remains a dangerous conductor in our lives because water is all around us all the time, and because it flows so readily, it fills the gaps between you and the source of the electrical charge that's gonna kill you, and if that charge is powerful enough you're gonna get a fatal jolt even if water isn't that good of a conductor because water doesn't have free electrons and thus it is not a metal.
Water remains somewhat shiny, because water is a liquid with respectable surface tension and so gravity pulls on it and it settles into a super smooth layer and even though it doesn't have free electrons. Light can still bound off of that smooth layer, and if you're standing at just the correct angle that very direct reflection will bounce right into your eyeball.
I use this phenomenon to my advantage all the time when making cooking. I'll be simmering something in a pan. I'll position one of my studio lights a little above the pan, and then I'll get behind my camera and move it up and down in relation to the food until I'm at just the proper angle to catch that super direct reflection that looks really sexy on camera. If I was better at geometry, I wouldn't have to look around for that reflection. I could predict where it would be relative to the incident of the light, and I could just put my camera directly there. Also I would be better at playing pool. Pay attention in geometry class, kids. That stuff is actually useful.
I paid attention — I just forgot most of it. The point is, you get any substance super flat and even, then it's gonna be shiny. Even a very flat matte-painted finish is non-reflective because at the microscopic level it isn't actually flat. It's filled with teeny-tiny irregularities that scatter light in a million different directions. That's why matte-finish paint feels rough on your skin. That's why you can't buff one of these fancy new matte-finish cars that I think were inspired by the matte-finish Batmobile from a few Batman movies ago. If you buff the paint job on one of those cars too much, it'll become shiny and you'll ruin in. A smooth, polished metal will simply be more shiny than a comparably smooth non-metal because the metal has lots of free electrons, which is why it's a metal, and the free electrons excite the protons, or something.
I still don't really know what a photon is.
Such as: they tend to be solid at the temperature we humans normally inhabit, with the notable exception of mercury, which is liquid at room temperature, but we call it a metal anyway because it is so conductive, i guess.
When metals are solid they are typically malleable, meaning you can squish them and bend them and they will stay bent — they won't just snap back into form, nor are they likely to break. You can hammer them out into a thin sheet and they'll stay that way. A metal also tends to be ductile, meaning you can get it hot and therefore soft and then shove it through a tiny lubricated hole and what extrudes out the other end like spaghetti is wire. Or at least that's one way of making wire. I confess I have trouble understanding how ductility is different from malleability. It seems to me that if you can draw metal into a wire, then it is, manifestly, malleable.
If it wasn't malleable, then you wouldn't be able to draw it into a wire. It would break when you squished it, or it would snap back into its original form. In fact, I just looked it up, and another, perhaps more accurate definition of ductility is that it is a material that resists tensile stress after having been drawn into a wire, meaning you can grab the wire at either end, pull on it, and it's unlikely to break. Apparently lead is malleable but not ductile — you can hammer it around and mold it with compressive forces but if you pull on it, tensile force, it breaks. Anyway, the materials we call metals tend to exhibit most of these traits but some of them don't exhibit all of them, and some of them only exhibit a couple of them and those we call metalloids. But it's not an exact science as to which is which. That's arbitrary. Most people on the internet seems to consider silicon a metalloid, because it's only a so-so conductor of electricity — many of its electrons are unfree, locked up in covalent bonds — and it's pretty brittle at common human temperatures.
When you get it super hot it becomes ductile, but at ambient temperatures that wouldn't instantly kill you, pure silicon is brittle and it chips and shatters like glass. This should hardly be surprising given that most glass is mostly silicon. Actually, most glass is mostly silica, which is the next of the four very similar words we need to untangle. Silica is much more common in nature than silicon. Pure, elemental silicon may occur in nature on Earth, but only in extreme situations. Like, in the 1990s, scientists collected fine particle material swirling around gasses in active volcanic vents in the Russian Far East and they found some halite crystals — halite is naturally occurring table salt, sodium chloride — and inside those halite crystals they found tiny crystals of elemental silicon.
But that's pretty much it for planet Earth. I have no idea if there are pure silicon asteroids floating around in space, just as there are pure crystalline carbon asteroids floating around, AKA the giant diamond asteroid discovered in 2004 floating around the constellation.
Centaurus. It's 10 billion trillion trillion carats. Strange things happen out there in the cosmos, weird things get ejected from stellar cores or whatever, so maybe there's giant chunks of pure elemental silicon floating around, like the ones scientists make in labs here on earth. Maybe there's a coffee asteroid out there. I wouldn't put it past the good folks at Trade. Coffee to send a ragtag group of miners into space to drill for space coffee. They go to pretty crazy lengths to secure all kinds of new and interesting coffee for me from the best independent roasters around. Trade Coffee, is of course, the sponsor of this episode.
Trade is a coffee subscription service that makes it so easy and convenient to discover new coffees at home, every day. You just tell them basically what kind of stuff you like and they do the rest. They have a whole team of professional tasters who taste hundreds of coffees every month looking for really special stuff.
Where trade buys a bunch of coffee wholesale and then they're highly motivated to sell it to you even if it's not that good or not that fresh anymore.
Trade partners with the local independent roaster. It's ultimately the roaster that sends you a bag of coffee in the mail, so it's gonna be really fresh, and fresh roasting really makes a big difference. Most coffee at the grocery store is stale.
Trade will hook you up with as many coffees a month in the mail as you want, as many as you go through. Anyway, scientists grow pure silicon crystals in the lab, but pure silicon almost never happens in nature on Earth, even though silicon is the #3 most prevalent element in our planet. Pedants, before you correct me, notice I said "in our planet," not "in the earth's crust.". I'm talking about the whole planet. Pure silicon basically never happens here, even though silicon is the #3 most prevalent element in our planet. Why not? Because the #2 most prevalent element in our whole planet is oxygen.
#1 is iron, but #2 is oxygen. We're swimming in oxygen, above and below ground, and oxygen readily forms an incredibly strong bond with silicon to yield silica. Silica is silicon dioxide. Silicon monoxide also happens, but mostly, apparently in space, where it can exist in its gaseous form, and where it is, I now read, the most prevalent form of silicon in the cosmos. But here on earth, it's silicon dioxide, AKA silica. Quartz is pure, crystalized silica. One particular crystalline arrangement of quartz is flint, and flint is where we get the name "silica." "Silicus" is Latin for flint. Silicate is an umbrella term that includes silica and lots of other minerals involving silicon and oxygen and other things, like feldspar, which has silicon and oxygen and aluminum and lots of other things.
Granite is usually mostly silica. I've seen the precise estimates very, but everybody agrees that a majority of the earth's crust is silica, or at least a majority of the earth's crust is silicon and oxygen. Silica is even more prevalent in sand. Most of the world's sand is mostly silica. On coastlines you also have a lot of calcium carbonate sand, which is the shells and coral skeletons bashed into tiny pieces by the waves and such. But inland, sand is almost exclusively silica sand. And lots of coastal sand is silica sand too, because it gets carried by rivers down to the sea.
Is the same basic reason why silica is a great material for making all kinds of things, cooking implements included: the bond between silicon and oxygen is incredibly strong.
You can pulverize any rock down into sand, which is just lots of very small rocks, but if you leave that sand out in the environment for a long time it will be subject to chemical weathering. The slightly acidic rain will fall on it and gradually dissolve it into something a lot finer than sand, like silt and then eventually clay. That's how you get clay — the chemical weathering of rocks. Minerals other than silica can be sand, but they don't stay sand for very long, at least not in geological time. The eventually end up as clay. Silica is resistant to chemical weathering, so after the physical forces of wind and water and such have pulverized it into pieces between 2 and.05 micrometers, AKA sand, that's about as much damage as the surface of this planet can deliver to silica, except in extremely hot places, like volcanoes, or in a glassmaker's furnace.
Glass is melted silica — usually mixed with some secondary ingredients like sodium carbonate, which lowers the melting point, and lime (calcium oxide) which keeps the sodium carbonate from making the glass water soluble — then you shape it and gradually cool it in a kiln so it doesn't shatter and the result is kinda like quartz, except its not a crystalline structure.
It's an amorphous structure — the molecules are stacked on each other in a disordered, topsy-turvy way that allows light to pass right through it and that's glass.
Now we come to silicone, with the silent "e" at the end of it. People who, for one reason or another, want to promote silicone as a "natural" material like to say that silicone is made of sand, and that's kinda true, but also, by that same logic, everything on earth is natural, because even the most exotic synthetic chemical started off as something already present on earth.
You can't make something out of nothing. Every synthetic chemical started out as some combination of natural precursors. And silicone, with an e, is most definitely synthetic. It does not exist in nature, at least not as far as anyone seems to know. It's debatable who exactly invented silicone, but the name was coined at the turn of the 20th century by an English chemist named Frederic. Stanley Kipping, who was playing with silicates — making polymers out of them, mixing them with other elements to make organic compounds.
Just because something is synthetic doesn't mean it's not organic, in the chemistry meaning of the word. In nature, though, the element silicon doesn't come up that often in organic chemistry. I mean, silicon does occur inside living things. All kinds of inorganic substances are common in living things, most notably water. Water is an inorganic compound, like silica. Silicon dioxide represents as much as 10% of the dry weight of plants, and grasses in particular. Rice has a ton of silica in its leaves and stems and husks and such, which is actually a big problem with rice as a crop. You have a ton of rice husk leftover after milling rice, so people burn the husks, and this mostly silica ash spews out into the environment where it raises soil pH and makes it hard for plants to adsorb phosphate, which is not good.
RHA - rice hull ash — is a big topic in agricultural sustainability, because silica. Why plants have silica is a debated topic. It does seem to provide a defense against herbivores. If you've ever tried to eat grass, it might have felt like you were chewing on sand, and this is why. Also, think of grass with really sharp edges — those edges are usually a row of tiny silica teeth. Your teeth would be worn to stubs if you tried to eat such grasses for too long. Ruminants, like cows and sheep, are specially evolved for this. This is why their teeth never stop growing, unlike our teeth.
They constantly wear their teeth down by chewing on grass, because silica, so their teeth never stop growing, to compensate.
In living things, even though silica and other common silicon compounds are considered inorganic.
Bond is just too strong.
This is why, it has been argued, that all life as we know it is based on carbon, not silicon, even though carbon and silicon are sisters. They are very similar, in many ways. They're in the same group on the periodic table, they both have four bonding sites each. But when silicon links up with oxygen, it tends to just stay that way, locked up in a solid — whereas carbon is a lot more reactive, it does a lot more interesting things. I'm ridiculously oversimplifying this.
Silicone was invented by people like Fred Kipping who were playing with combining inorganic silicates with organic groups into the same molecule. The word organic, in the world of chemistry, refers to compounds containing carbon, and specifically carbon-hydrogen or carbon-carbon bonds, because such bonds are ubiquitous and essential in the chemical compounds that comprise living things. Kipping and some other guys around the same time basically said, what happens if we bond carbon to silicon? That's not a thing that really happens in nature. And the result was a new subfield called organosilicon chemistry. One particular polymer Kipping played with in his lab was a long silicon-oxygen chain with two organic groups hanging off of the silicon atoms. A silicon atom has four bonding sites, just like carbon. In this new substance, two of those bonding sites on each silicon are occupied by oxygen on either side, holding hands in the silicon-oxygen chain, and the other two bonds sites are linked up with organic groups — specifically phenyls, in the case of the particular polymer he was working with. Phenyls are carbon-hydrogen rings, and they were hanging to the side off of this silicon-oxygen chain.
The chemical formula of this new thing Kipping was working with reminded him of the chemical formula of kind of ketone. Everybody knows what ketones are now because of the ketogenic diet. The chemical formula of this new substance reminded Kipping of the formula of this particular kind of ketone, but with silicon instead of carbon, so he named this new thing silicoketone, eventually shortened to silicone. And now you know the rest of the story. Show that radio joke to your grandpa, he'll love it. Anyway, because silicone is structurally not at all similar to this ketone, scientists now regard "silicone" as a misnomer, but it stuck, as so many early scientific misnomers did. The preferred scientific term for silicone these days is siloxane, but most non-chemists call it silicone, so I'm gonna call it silicone. Silicone is generally considered to be inorganic, or sometimes people describe as being kinda quasi organic, because it does have organic groups in it, but the main repeating backbone that makes it a polymer is silicon and oxygen — no carbon-carbon or carbon-hydrogen bonds in the backbone — so it's inorganic.
But it requires organic precursors to make, namely hydrocarbons — fossil fuels. They make silicone by extracting elemental silicon from silicates — rocks — and then combine the silicon with hydrocarbons and oxygen in some order and in some set of conditions to get the particular chemical structure they want. Last week when we were talking about gas stoves and whether they cause asthma, I said something. I say all the time, which is that there are a dozen reasons to kick our various fossil fuel addictions — so not all the reasons have to be valid or 100% confirmed. Right here is one of the other dozen reasons. Fossil fuels are finite, nonrenewable, and we need them for lots of purposes other than fuel. We need hydrocarbons from the ground to make silicone and plastics and such, and it would really suck if we burned all of the accessible fossil fuels before converting to renewable energy, because then we'd be out of the raw materials necessary to make silicones and plastics and lots of other things. Plastics are kind of the organic equivalent of silicone.
Plastic is an example of a synthetic organic compound. Plastics are long chains of carbon — carbon holding hands with other carbon on two of its bonding sites — with hydrogen attached to the other two bonding sites on each carbon. And chemists vary the properties of the plastic by attaching slightly different side chains to those hydrogen bonding sites on the main carbon chain. Silicones can be made to have all kinds of different properties by varying exactly what organic stuff you have hanging off of the main silicon-oxygen chain. But all silicones share a set of very interesting properties.
So they tend to be nontoxic. Silicones are terrible at conducting heat, which is why you can make oven mitts out of silicone, and because that core silicon-oxygen bond is so strong, silicone is very thermally stable.
You can melt or burn silicone but not at temperatures you're likely to find in the kitchen. Silicones are also resistant to cold — they don't go rigid until you get to ridiculously cold temperatures, like 200C below freezing. Silicones are hydrophobic — they do not stick to water. Thus silicones can be used as waterproof coatings, and are an alternative to PFAS chemicals for that purpose. In fact, silicone coatings are used on the windows of supersonic jets — aircraft that move so fast and create so much friction with the surrounding atmosphere that windshield wipers would just blow right of off and other hydrophobic coatings would burn right off, but not silicones, which can take a lot of heat.
Silicones are resistant to microbiological growth, because they are so hydrophobic. Germs have trouble sticking to silicone as do the nutrients that germs need to grow. Silicones are usually flexible and elastic, though some can be quite rigid.
Silicone sheets usually don't crease along the folds, which makes them great for baking sheets, along with their nonstick and thermal stability properties. What silicones really resemble is rubber, more than plastic. Silicones allows you to make rubber-like material that is far more heat stable than natural rubber, which is a polymer made from the latex tapped from rubber trees. I remember when I was in high school I had these natural rubber-soled shoes, and my high school was a super old building, not up to modern code, and so it had these exposed hot-water pipes just running through the hallways where you could touch them and burn yourself, and. I remember being really bored one day waiting for my bus and I was standing next to this exposed, vertical hot water pipe and I touched my shoe to it and the sole melted against the pipe. I found this fascinating and I stood there melting my own shoe until the bus came and that's the kind of teenager I was. With silicones, you can make rubber-like materials that don't melt at any remotely normal temperatures. Very useful for the kitchen.
You can bake in or on silicone, and because silicone is a bad heat conductor, the surface of your food that's touching the silicone won't get very brown compared to the rest of the mass. That's very useful in certain things that tend to get too brown or even burn on their surface in the oven. And don't forget the cold. Because silicone doesn't freeze at normal freezer temperatures, you can use it to make freezer molds, like ice cube trays. Because the silicone remains flexible at low temperatures, you can simply bend it and peel it off the surface of the frozen thing, plus it's hydrophobic so it's not inclined to stick to the ice cube anyway. That flexibility makes silicone ideal for scraping stuff out of bowls. You press with the silicon spatula and it simply molds itself to the contours of the bowl, thus allowing you to scrape every last bit of your cake batter out of the bowl. I think these rubber-like qualities cause us to associate silicone with rubber, and therefore it makes silicone seem more natural and warm and fuzzy than it really is, because we know rubber is a natural thing as opposed to plastic, but silicone is every bit as synthetic as plastic is.
Some people consider silicone a kind of plastic, even though it's chemically very different. Plastic is, after all, an adjective, not a noun, though we have noun-ified it. Plasticity is simply a property, and it can be exhibited by all kinds of chemical structures. Plasticity is the quality of being easily shaped. Silicones are easily shaped, like hydrocarbon plastics. They are synthetic, like hydrocarbon plastics, and they're also made with hydrocarbons — you need them for those organic side groups that give your particular silicone its particular properties. Silicone is a petroleum industry product, just like plastic.
Most silicone products on the market are mixed with other ingredients, and so everything that can be bad or potentially hazardous about those secondary ingredients is gonna be bad about your silicone spatula, or whatever it is. And there is reason to think that silicone itself — siloxane — is not as totally inert and therefore totally safe as people think it is. I mean, I am not here to fear monger about silicone or anything else. All cooking materials have pros and cons — there are potential health hazards associated with every kitchen material I can think of. I'm just telling you about the ones associated with silicon now, because you asked. While silicones are super hydrophobic, they are somewhat less lipophobic. They're not as chemically similar to fats as carbon-based plastics are, but there is some chemical affinity between silicones and fats that is way above my head.
Regardless, there's a 2011 study out of Germany where they observed actual silicone, siloxane, migrating from silicone bakeware into food, and the amount of migration increased with the fat content of the food being baked. There's a few similar studies you'll see if you just google scholar "silicone bakeware safety" or some similar set of words. People have done other studies where they held fatty liquids, like milk or baby formula, in silicon bottles for a long time and looked for any siloxanes leaching out, and they didn't find much. The only really significant leaching they observed was when they left alcohol — booze — in contact with silicone for several days. I don't think there's a big silicone liquor bottle industry, but there is a big silicone baby bottle industry, so it's good that people are investigating that, it seems so far there isn't much to be worried about there. Is it bad if you ingest silicone? Maybe. It's one of these things that people considered to be biologically inert because it doesn't seem to have any acute effects on people, but it may have chronic effects on people with consistent exposure over time. That's a distinction we talk about a lot on this pod, and a fellow emailed the other day saying he's mad about how corporations basically get to test their products for chronic toxicity on us, the buying public, and I definitely understand that frustration.
On the other hand, it's really hard to test things for chronic toxicity in laboratory. You can't wait around for forty years while the human test subjects in your trial slowly do or do not develop a cancer that may or may not have been caused by your product and there's virtually no way of confirming if it was, on the individual level. You have to look for correlations on the population level to spot a minor increase in cancer risk associate with a given exposure. They test for chronic toxicity on animals, but of course those tests have limited value. Anyway, if you want to read through some of the little research that has been done on this topic, search siloxane toxicity — a tip for searching scholarly sources is if there's a more technical name for something, use that — siloxane instead of silicone — and you're gonna get more serious, more academic, scholarly sources.
People who really know what they're talking about say siloxane, at least some of the time. Earthy crunchy bloggers who make their living off panic clicks probably just say silicone. And keep in mind that silicone isn't just one thing — there are many, many different siloxanes that chemists have come up with, and they probably all have different biological effects.
But anyway, some animal studies have linked chronic siloxane exposure with elevated cancer risk, and some studies have shown certain siloxanes might function as endocrine disrupters, the way plastics can, which might impair fertility and other stuff associated with your endocrine system — your hormones.
Silicones are incredibly persistent in the environment, just like plastics and PFAS chemicals and all that. That core silicon-oxygen bond is just as stable as can be. If you want evidence, go to the dessert and look at the sand. Mother Nature is throwing everything she's got at those little silica rocks and yet they keep on keeping on. So why do we consider silicone to be a greener alternative to plastics, even though they are synthetic petroleum products that don't biodegrade and that may pose some environmental health risk? Is silicone recyclable or something? Yeah silicone is recyclable, but not really, in practice. I don't know of any city recycling services that pick up silicone. You have to take it to a special facility.
Apparently a common thing you can make out of recycled silicone is industrial lubricants, and that's good, they need those. But you're not gonna find a lot of solid recycled silicone products. I think the main green argument in favor of silicone is how reusable it is.
Loose and leach out here and there, but in general, silicone tools are very stable, very durable.
Silicone bakeware does tend to get brittle after it goes through a lot of baking cycles, and it can break. It's probably less durable than a metal cake pan, but do people really use the same metal cake pan their whole lives, or do they treat those as disposable too? The metal might be super durable, but not the PFAS nonstick coating that most metal bakeware comes with these days. That wears off, and posses all kinds of environmental health hazards. People throw away the pan, they buy a new one.
And I think that's a fair comparison with silicone bakeware, because people usually reach for silicone bakeware for its nonstick properties — the fact that you can just peel it off the cake or the cookie or whatever, like the back of a sticker. And speaking of cookies, what about parchment paper? I use parchment paper all the time. It's silicone-impregnated paper. Great stuff. But it's disposable. You use it then you throw it away. A silicone baking sheet is at least reusable, even if it isn't recyclable, in practice. Silicone got very popular for storing leftovers and such as people tried to get away from plastic, because of the problems with plastic and endocrine disruption, but for all we know, silicone may be just as bad on that score.
In fairness, a container like my Anchor glass containers is mostly glass — only the lid is silicone, so that's way less silicone or plastic in contact with your food. And, in practice, I find silicone containers to be more reusable than plastic containers because they don't melt in the dishwasher. All of my plastic Tupperware and such, it all eventually warps in the heat of the dishwasher, or I leave it on the counter too close to the stove and I melt a hole through it. It's possible to burn or melt certain silicones in your kitchen — don't hold your spatula right in the blue gas flame, I don't want to know what happens — but you really have to go out of your way to melt silicone stuff at home. So why am I feeling like I want to give up on silicone? It's because of the smell. Silicone traps yucky food smells and transfers them around to everything else. Why it does this, I'm not entirely sure. I could not find any scholarly investigation of this specific topic, though I easily could have missed it.
Here's some things I can tell you. Silicones tend to be gas permeable. They don't let water though, but they can let gasses through, and this a property that is valued by medical devices makers who need gas-permeable membranes for all kinds of things. Odors are gaseous, by definition, so maybe some of them pass into that gas-permeable silicone and get stuck there, for whatever reason. One time I was in a lab at a major university talking with some scientists who research health hazards associated with plastics, and I said, "So do y'all use silicone instead at home?". One scientist turned to the other and said something to the effect of, "Do you feel cool with silicone, knowing that we use it in the laboratory for the express purpose of absorbing hard-to-capture things on the microscopic level?" And the other scientist laughed and shrugged. Take that story for what it's worth, which is just two people with relevant expertise having informal, off-the-record chats. That's not a fully-considered scientific opinion fit for publication.
I suppose silicone is made from silica — sand — and people use silica as an odor absorber all the time. Think about litter boxes. But sand absorbs odors, I think, purely though force of surface area. Odiferous chemicals can and do settle on surfaces, and because each grain of sand has its own 360-degree surface area that's an astounding amount of surface in a litter box full of sand. I'm not sure how relevant that is to silicone kitchenware.
Surface area if it were porous.
This is a very hot topic in the sex toy manufacturing and retail community, and according to them, food-grade silicone is often more porous than medical-grade silicone, therefore the best manufacturers in that particular market try to source medical-grade silicone, as it is less likely to harbor smells and germs, or at least that is the anecdotal experience of people working in the sex toy business who write about it online.
In the kitchen, I'm less worried about germs than smells, because no life form can survive the heat of my dishwasher, with the possible exception of a tardigrade or some other extremophile, none of which are common food-borne pathogens. I'm not the only person who is irritated by the odor-absorbing properties of silicone. Google it if you're skeptical. You'll read first-person accounts from sex toy users and. Instapot users. Instant Pots are the hip new breed of standalone, electronically controlled pressure-cookers. It's basically a slow-cooker crossed with a pressure cooker, and to maintain the high-pressure environment inside, it needs a flexible seal that can handle high temperatures — sounds like a job for silicone. There's a removable, washable silicone ring in every Instapot-style device, and it tends to get smelly, perhaps because people use Instapots for long-cooking things, and that simply provides the necessary time for aromatic compounds to defuse into or to otherwise permeate the silicone.
Maybe the pressure makes the situation worse, I don't know. But people complain about the ring passing flavors from one dish they cook to the next. The ring is removable so you can wash it, but washing with soap doesn't seem to do much. Soap molecules are very big, and I wonder if they're just too big to get into the micropores where the smell is hiding. This is a great opportunity for a food science or materials science graduate student. As far as I can see, no one has directly investigated the silicone odor problem in publicly available scientific literature. Get in the lab, figure out what's going on there. This is apparently also a topic of conversation in prosthetics.
Artificial limbs generally have a soft, silicone interface where they meet the skin of the human body they are serving, and that silicone tends to get smelly. That's a group of people who really deserve some help, as opposed to people like me who are just trying to make cake icing that doesn't taste like my spatula. Fats have great chemical affinity with lots of aromatic compounds, so they tend to traps smells to which they are exposed. I don't know, I'm sick of it. You can soak smelly silicone in a vinegar solution overnight, that works pretty good, but then it smells like vinegar. You can rub it down with a baking soda and water paste, and let that sit overnight — that works pretty good, but I'd just rather not. For spoons and such I'm using wood — bamboo, specially — for almost everything, and I think I'm gonna go back to natural fiber basting brushes too. They're renewable, biodegradable — porous, yes, but soap seems to do better on them, I suspect because the pores are bigger.