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How I am De-scenting my Silicone Thermos Seal

First of all, I always get silicon and silicone mixed up, so please don't get offended if I do here. The one I'm talking about is the one that's squishy, like cartilage, not the one that's hard and makes glass. But there's two common characteristics between the squashy and the brittle uses of this element: high temperature resistance, which is why they are used in circuit board construction and pressure cooker gaskets; and their ability to absorb and release "volatile organic compounds (VOCs)" - that is, they *stink* after a while.

My misadventures with the cartilaginous silicone compound has included accidentally brewing rather insect-filled sake in a rice cooker (irrecoverable: the insects got into the seams of the lid and then I broke the handle); moldy coffee and tea in various bottles and thermoses; and finally, after removing the smell of mold from one such Thermos by leaving it soaked in dish soap and vinegar in a hot car for a week, I was left with an unmistakable chemical smell that was very off-putting when I tried to drink... anything at all. The smell got worse when exposed to hot liquid (because that's what a Thermos is designed for, after all) and had no reduction when soaked in vinegar, salt, baking soda, rubbing alcohol.... My creativity eventually failed me.

And so this Thermos had been out of service for years, until this last move -- unable to find my primary travel mug, and desperately needing a hot drink on a cold day, I reassembled the thing and quickly remembered why I had put it aside.

So a quick Google search led me to this article, by someone else who'd had much the same trial and error over a pressure cooker gasket and an ice cube tray, and she'd had success with baking in the oven at 250°F and 450°F respectively. (Read her article for more details and caveats). 

[Now an interesting sidenote here, which may explain my technical knowledge or lack thereof, is that in the interim of failing to get the stink out and reading this article, I'd actually done a stint as an troubleshooting engineer for the equipment used to fabricate printed circuit boards (PCBs). I was eventually counseled for not learning fast enough (yay ADHD) and not making the customer feel like I was confident and in charge of their equipment (yay autism) and left the company, getting diagnosed for those two genetic disabilities less than a year later. Okay, maybe that wasn't such an interesting sidenote... but now you know.]

I was already not using this item, so destroying it wouldn't cost me anything; but the snag is that I don't trust the gas oven in the place I've relocated to - so I've used my toaster oven. The concept is simple: heat makes molecules wiggle more, so the stinky molecules get free easier. This is called outgassing. One thing to keep in mind is that the stinky molecules also get caught easier, which is what made the seal stink in the first place, so the trick is to keep removing the stinky molecules before they can return to the silicone object. A big oven would have convective airflow, but since I'm not using a big oven, opening the door and "blowing out" the old, stinky-molecule-filled air every few minutes should work fine.

Yeah, I'm totally a scientist. Let's just say there's a lot more alcohol wipes and forced airflow involved in removing outgassing from silicon "boats", or the glass tray that holds baby circuit boards while they're being built, one atom at a time.

Not knowing or really caring what the max  temperature rating for this seal is, I've put it in for about twenty minutes at just over 250°F (I figure I'm accounting for the house being at 67°F). Because i didn't want to chance ruining my oven if it melted, I made a little plate out of tinfoil, but it looks like that wasn't necessary. After twenty minutes, I pulled it out and it stank only a little less strongly than ever, so i washed it under really hot water with Dawn antibacterial soap and - it didn't stink any more. As it cooled, the outgassing stopped, meaning that even after baking only twenty minutes, right now, it's probably going to taste and smell fine at boiling water temperature (200°F). However, when I put it back in the oven and got it back up to temp (275°F) it started stinking again, meaning there's still VOCs embedded deep in the plastic and they will work themselves to the outside eventually. Guess I'll just keep baking!

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