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How flammable is rubbing alcohol?
July 20, 2014 12:17 PM   Subscribe

We made some tie dye tshirts using Sharpie markers and rubbing alcohol. The instructions say to set the ink, put the tshirts in the dryer for 15 minutes--but won't I set the dryer on fire?

I want to trust what the website says about putting the tshirts in the dryer for 15 minutes but I'm worried about it. Does anyone know the anything about this? Any chemists out there?
posted by biscuits to Grab Bag (15 answers total) 2 users marked this as a favorite
 
You're supposed to let it dry before putting it in the dryer: "After your shirt is completely dry (alcohol is flammable, so don’t use heat on a damp shirt), set the colors by tumbling the shirt in a hot clothes dryer for ~15 minutes."
posted by effbot at 12:20 PM on July 20 [4 favorites]


Rubbing alcohol evaporates very quickly. Your t-shirts would need to be noticeably wet with the alcohol for there to be any danger.
posted by pipeski at 12:21 PM on July 20


If you wait until the shirt is dry per the instructions, the rubbing alcohol will have evaporated and the shirts are safe to put in the dryer.
posted by tealcake at 12:22 PM on July 20 [3 favorites]


Roll up a newspaper into a long tube. Hold one end, and set the other end on fire. Wave the burning end a couple of inches over the tshirt. If it doesn't burst into flames, the dryer won't be able to ignite it either.
posted by Sophont at 12:27 PM on July 20 [2 favorites]


Hah! I like Sophont's rather direct method, but as others have suggested, just let it dry first. Rubbing alcohol will vaporize pretty quickly in a well ventilated area.
posted by Nerd of the North at 12:42 PM on July 20


Tumble dryers run at about 160 C, whereas spontaneous ignition of ethyl alcohol occurs at 365 C.
posted by Segundus at 1:11 PM on July 20 [3 favorites]


Actually some might go hotter than that, but you've still got a good margin.
posted by Segundus at 1:19 PM on July 20


Tumble dryers run at about 160 C, whereas spontaneous ignition of ethyl alcohol occurs at 365 C.

Some gas dryers have open gas jet flames.
posted by Jahaza at 1:41 PM on July 20 [4 favorites]


And some electric dryers have elements that heat to glowing temps.
posted by Good Brain at 3:25 PM on July 20


Tumble dryers run at about 160 C, whereas spontaneous ignition of ethyl alcohol occurs at 365 C.

And spontaneous ignition of isopropanol (rubbing alcohol) is at 399 C.
posted by hydropsyche at 6:00 PM on July 20


Sooooo even assuming that my dryer gets to 399C, it would not ignite because the tshirt is dry?
posted by biscuits at 7:44 PM on July 20


It won't ignite because most of the alcohol has evaporated off by the time the t-shirt is air-dried.
posted by sparklemotion at 7:50 PM on July 20 [3 favorites]


Step seven has it. Alcohol evaporates readily at normal temperatures. A tshirt that feels dry, and not cool because that indicates evaporation is still taking place, is what you want.

The thing that makes dryers hot [electric element or flame] is a higher temperature - especially with flame dryers - than the drying chamber so you are prudent to be concerned. I wouldn't throw an alcohol soaked shirt into a dryer. But, if you let the alcohol evaporate, preferrable in another well-ventilated room you are in no more danger that if you were just doing a normal load of laundry.

The flame temperature of natural gas is between 900–1,500 degrees Farenheit. This is well above the autoignition temperature of alcohol.

Just let the alcohol evaporate in a well ventilated area and you'll be fine.
posted by vapidave at 4:03 AM on July 21


Sooooo even assuming that my dryer gets to 399C, it would not ignite because the tshirt is dry?

Not from the alcohol, since it's gone. The tshirt itself may catch fire, though, since cotton self-ignites at around that temperature (a quick Googling tells me that the auto-ignition temperatures for textiles is typically in the range 250-600 °C, but US standards require dryers to shut off at 120 °C so you should be safe.)
posted by effbot at 11:14 AM on July 21


Thanks everyone!
posted by biscuits at 11:00 AM on July 23


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