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Comment by IgorPartola | Hacker News Reader

Oily rags are super dangerous. Depends on the type of oil or thinner but definitely something to keep in a small sealed metal container.

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Linseed oil is the usual culprit. It oxidizes more readily than other oils at room temperature, and a pile of rags can insulate enough for the center to reach autoignition temperatures. The low smoke point for linseed oil also makes it well-suited for seasoning cast-iron cookware (only be sure, please, not to use boiled linseed oil, as it contains lead.)

Linseed oil is just flaxseed oil, and I've found that the latter term is used in cooking contexts, whereas linseed oil is a term used in various industries that use industrial grade flaxseed oil.

I make this distinction because when I went to buy "linseed oil" to cook with on Amazon a while back, it brought me to various linseed oils that were not meant for human consumption.

>low smoke point for linseed oil

I would naively think you would want an oil with a high smoke point for seasoning. Can you elaborate on why a low smoke point is preferable?

My wife uses linseed oil on cast iron. Almost as good as non-stick. Linseed oil has a lot of triply unsaturated α-linolenic acid, which is reactive (due to multiple double bonds) and supports polymerization. A few thin layers of linseed oil added to cast iron and baked to the smoke point create a beautiful sheen and make it easy to clean.

Finally, a reply that is correct. Thank you; too many people leave seasoning up to being some mystery when it's really just that straightforward.

FWIW, I wrote this up a few years back after I went down the rabbit hole of seasoning pans, only to find that it's actually really simple and just as you describe: https://nuxx.net/blog/2014/01/24/well-seasoned-cast-iron-pan...

You want it to smoke when seasoning. That's an indication that free-radicals are being created which set off the polymerization of the oil and create the seasoning. Low smoke-point oils are more convenient because they start polymerizing at lower temps.

You don't want it to smoke when cooking, because ingesting the free-radicals is generally considered unhealthy ;)

The free radicals don't stick around for very long, maybe seconds before they react with something else.

And cooking in general create a bunch of carcinogens like acrylamide, etc. You can reduce it, but it's tough to eliminate it completely.

This is a glaring connection I rarely see people make.

In fact, I've been banging on about it for 15 or so years, and, I kid you not, you're the first person I've seen being this up.

Strange!

Unusual cross section of knowledge: I studied nutritional medicine in a formal capacity for four years 2000 through 2003 inclusive, and I'm also a welder by trade.

At the cross roads of knowledge domains interesting conclusions can be drawn, and sometimes fruitful cross pollination occurs. One thing about the successful founders that I know is that they are not confined to just one domain, and I have been wondering for a long time if that is a trait that helps them to be successful.

Why would boiled oil have more lead?

Lead oxide is a catalyst to polymerization. For wiping down and protecting wooden tool handles it's nice to have the oil harden quicker at room temperatures.

Probably not a good idea to store superglue and cotton together.

Combustion probably unlikely, but non-zero chance.

That reminds me of something. When I was a kid, I dumped a bunch of superglue on a cotton ball once and it didn’t even warm up. I wonder now what the actual conditions are for a superglue cotton fire.

On an industrial scale, sure. For home/hobby use, laying them flat until dry and stiff is plenty sufficient - I treat all such exothermic wood finishes with a great deal of care, but so long as you're not piling up rags or compressing them into a ball you're fine.

Personally I store them in a fireproof container meant to store ashes and inside that they are in ziplock bags. After I am done using them I burn them to get rid of them. Helps that I don’t need stuff like that often.

The primary danger from oily rags is probably from slip and fall on the oil you're working with.

It takes very specific conditions to get oily rags to ignite. As a rule you're gonna have a hell of a time getting any lubricating oil specifically designed not to degrade in a high heat environment because the chemistry that keeps those oils stable over a long time at 200deg (or whatever) makes them very hard to ignite.

A friend left an oily rag in a bucket on a ladder where it was eventually exposed to midday sun; that was enough to ignite it. Fortunately we saw it just as it happened.

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