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Minwax fast drying polyurethane risk of spontaneous combustion?

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  • callee
    Like Julian says, I always err on the side of caution with solvent rags. I hang them for the night and discard them the next day.

    Side note, rags aren't the only combustion you have to worry about with solvent products: the fumes can build up in the air as well. Make sure you have sufficient ventilation when using them. Couple years ago my friend in Toronto had to vacate her apartment: the super was refinishing the hardwood floors in the unit below. It was winter, so he had all the windows closed, and so the fumes built up and were ignited by his open element space heater. I believe the guy was killed in the explosion. Obviously that's an extreme case, the most you'd probably get is a headache, but you should ensure sufficient ventilation all the same, and a respirator mask is also recommended.

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  • EFZauner
    My understanding of spontaneous combustion of oil soaked rags is unique to "drying oils" that harden via crosslinking when they are oxidized. Linseed oil, tung oil are the most common. The oxidizing breaks the double carbon bonds and creates heat that builds up if the rag is all bundled together. I recall well as a child because my mom used to touch up all our teak and walnut furniture with linseed oil-turpentine mixture regularly and told me about the fire hazard. Loved the smell in the house after she did this! Petroleum based solvents such as mineral spirits or acetone-toluene based lacquer thinners do not oxidize when exposed to air this way. Never in an auto garage to they worry about spontaneous combustion of rags.. even diesel soaked. However...seems like some biodiesels may have double bonds left over from their vegetable heritage... As for putting them outside. yep just for the smell..

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  • Julian
    You do not tell us whether the product is solvent based or water based.......though I assume its solvent based it or you would not be fussing.

    Any solvent soaked rag is at risk of self ignition under the wrong set of just operate on that basis and be safe and live long and wake up in the morning to find you still have a workshop (or garage, whatever) rather than a smoldering ruin.

    There are "closed or self closing cans" or water filled cans that you can stick your rags or brush into....but it is equally safe to spread out/hang up the rag(s) so that they cannot build up and contain heat (which could potentially then cause ignition).

    I keep a metal pail or gallon can around (with a lid) and stick the items in there and close the lid.......this is safe and easy and quick and does not the event that the vile rag does heat up and or ignite (never has in 35 years).....the lid is closed so the fire would use up all the oxygen in short order and put out the problem.

    Anyhow, its not a big deal .... just know that the possibility of self ignition does exist, albeit slim and unlikely ....and take a simple step to avoid it.
    Putting the offending items out on the porch works fine...but even there I would spread the rag out so the product can evaporate or dry so that when you bring back in any risk is gone.

    Onwards to victory!

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  • Minwax fast drying polyurethane risk of spontaneous combustion?

    Hi all,

    ​​​​​​Just started woodworking a few months ago. I'm in the process of finishing some coasters. I decided to apply minwax fast drying polyurethane to help build a protective layer on the coasters. From the reading ive done on forums, it doesn't seem like this stuff is at risk of spontaneous combustion. Obviously it's flammable (so we shouldn't be careless with it), but it didn't seem like anyone had any issues with spontaneous combustion of polyurethane.

    As a last check, I went to look at the SDS for this product and they state there is the risk of spontaneous combustion (see attached photo).

    I know with certain oils (danish oil ,Tung oil), there's the heat generated when the oil "drying" that puts rags at risk of spontaneous combustion. But I couldn't find any info on this minwax stuff generating heat though.

    Anyone have any thoughts/experiences? I was about to leave my foam brush and rag to dry in the workshop but instead left them out on the porch just to be safe.
    Attached Files