Dr. Silicone (How I Learned to Stop Worrying and Love Siloxane Bonds)

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Dr. Silicone (How I Learned to Stop Worrying and Love Siloxane Bonds)


Editor’s Note: Samantha Rose is a trained designer, not a material scientist, but when she realized there was a niche in the market that needed to be filled, like a true maker, she aspired to learn all she could about the materials and manufacturing needed. We met her at World Maker Faire New York, where she shared the story of her journey to maker pro.

I was reaching for a spatula from a drawer in my kitchen. I had somehow accumulated six or seven from which to choose. Maybe you have a drawer like this too – some spatulas with silicone blades, some with plastic, some with regular wooden handles, some with metal or plastic or bamboo. As I scanned them, unsatisfied, I wondered: why do I have seven spatulas, and why are they all so inadequate?

I picked one up. Silicone blade: flexy, heat safe, colorful. Wooden handle: burned, and warped from the dishwasher. I pulled apart the blade and handle to find some dried residue from the last use. I thought, “Why don’t they just make these out of one piece?”

A unibody silicone spatula was the answer. It wouldn’t burn or melt on the stove, or warp in the dishwasher. It would be seamless and strong, and easy to clean. But it just didn’t exist. I looked in stores everywhere, with no luck. Knowing what I know now, perhaps it was the price — they’re expensive to produce! But then again, maybe it was just that no one had really thought about it all that much before. Anyhow, I wanted one. I wanted to make one.

Thus began a two-year quest for silicone expertise and spatula perfection. I wanted to make a spatula that would last forever, with FDA-approved food-grade silicone and a high-heat safety rating. (I molded a couple prototypes at home, thinking that if it worked right I’d make a few for friends and family as gifts. The models were cool, but lacked polish.) Once I made the decision to move to a professional manufacturer, more interesting questions arose. How do we optimize flexibility in the blade? What material should we use in the core to give it balance and minimize heat retention? And most of all: how heat resistant can we get it to be?

GIR Spatula Wireframe

As the R&D phase continued, the question of heat resistance in food-safe silicones became something of a fascination. Some utensil manufacturers have claims as low as 350°F and others up to 800°F on their packaging. There are dozens whose labels say 600°F, 650°F, or 700°F. The variation in temperature claims is vast, and confusing. After all — and I know this, because now I’m a silicone expert — there are a limited number of “ingredients” that can go into silicone that qualifies as food safe under FDA regulations. Add the wrong stuff, and you’ll end up with an elastomer capable of withstanding higher temperatures, but better suited for contact with jet fuel than scrambled eggs.

I read, and googled, and read some more — all in search of the “best” materials available. I interviewed several scientists with significant theoretical and practical knowledge of silicone properties. I sent samples to a lab for testing.

The hard science behind thermally stable elastomers is fascinating, and perhaps best left to the likes of Robert A. Rhein, who wrote a comprehensive review on the topic on behalf of the Naval Weapons Center in China Lake, Calif. As you may have deduced from the previous sentence, the guy is a bona fide rocket scientist. And in a 42-page report, he lays out a summary of silicone elastomers that deals with their thermal stability as tested in an inert atmosphere, in air, or in the presence of water (each condition, naturally, produces different results). His report became my bible, finally leading me to the conclusion that household brands who tell you that their silicone is heat resistant above 550°F are just plain wrong.

It’s important to point out the difference between “stability” and “reactivity” here. Inert-atmosphere tests measure the stability of the silicone by itself. Real-world use has to consider reactivity, most commonly with oxygen and water. A wooden spatula will char because it reacts with oxygen; at prolonged exposure, it will break down and release gas byproducts, and then these gasses will combine with oxygen — that, chemically, is what happens when it catches fire. Testing in an inert atmosphere (argon or nitrogen) provides a reproducible, controlled measurement, but it cannot be used alone to evaluate the safe usage temperature of any material. “By the numbers,” these inert atmosphere tests show a higher result — a result demonstrating stability, but not reactivity. A result that’s fascinating to me as a nerd, but not that useful to me as a home cook.

In a real-world cooking environment (i.e. outside the inert gas testing chamber of a laboratory device), actual heat resistance limitations are rather narrow for food-safe silicones, and land you in the mid-400°F range for prolonged exposure. Instantaneous heat around 525°F is okay. Above 550°F, you’re looking at very rapid degradation. On the molecular scale, polymer chains rearrange and gas byproducts escape; at the macroscopic scale, physical properties like color, texture, and brittleness are permanently altered. At 986°F, a sample tested in the presence of oxygen will have decomposed completely — residual, modified polymers and gas byproducts will be all that remain.

Gir Spatula Mold

So why do some companies claim higher temperatures? Chalk it up to marketing. Hypothetically, certain lab tests conducted in inert atmosphere might deliver a higher number to an otherwise well-meaning marketing exec making decisions about what to write on a piece of packaging. And bigger sounds better. But that doesn’t seem fair to consumers, whose kitchens are filled with oxygen and flames rather than argon gas. Here’s what’s fair: we’re all using the same silicone. All of us kitchen brands. Food-safe silicone has a limited number of ingredients, and a thereby limited range of characteristics and properties. And it’s all heat resistant to somewhere around 450°F–525°F. It’s a range based on the cooking environment, and the amount of time the material is exposed to heat, and a host of other factors.

At GIR (Get It Right), we chose to publish 464°F as our “official” heat resistance temperature. It’s a conservative estimate. You could go to 525°F momentarily without any adverse effects. But for prolonged exposure, and for the kind of heavy-duty use we want to advocate for our “indestructible” spatulas, 464°F is a more trustworthy threshold. I like to think of it like a speed limit — it’s a guideline designed to keep you safe. Keep it under 464°F and you can turn away from the stove, chop another onion, and come back without worrying about burning your hand when you pick it up. Test the speed limit if you want, but just know that you have to pay extra attention when you’re driving fast. Incidentally, the burn point of every common cooking oil is well below this limit. Practically speaking, you’d ruin your dinner before you could have any effect on the spatula’s structural integrity.

Cooking with the GIR Spatula

This deep-dive into silicone research has ultimately informed our product design and the making process, but also presents an interesting marketing challenge. It’s hard to feel like the only one in the room who’s done the assigned reading. Especially when the answers are elusive and merit hours upon hours of research. The marketer in me wants our spatulas to be heat resistant to 600°F. But they can’t be — it just doesn’t work that way. When you see it on someone else’s packaging, don’t buy it. If you’re asking Samantha the Chief Science Officer, I’d tell you that science always wins, and that you shouldn’t believe everything you read (unless it’s written by a rocket scientist).

We’re making new products now, moving beyond spatulas and eventually beyond the kitchen. To fund the venture and share our story, we’re on Kickstarter with a campaign for mini, skinny, and pro spatulas, and expanding to a full line of flippers, spoons, and scrapers. They’re practically indestructible, and yes — they’re all heat resistant to 464°F, just like my research said they would be.

GIR Mini Skinny Pro

Hacking your own education is a hot phrase these days, and I guess you could say that’s what I did to become a silicone expert. First, I kept it fun. I pulled knowledge from a variety of sources, focused on efficiency and specificity of search. I was persistent when it seemed like there weren’t any solid answers, never held back from asking questions. I related it to something tangible, make-able — to give the knowledge a purpose and let it drive creation. And I made some phone calls. Dr. Rhine is happily retired in California, and he says I’m doing the right thing.

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