Denatured vs 90% isopropyl alcohol for prep work/cleaning?

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I’ve heard people specify “denatured alcohol” in discussing boat repair prep work. But I’m still unclear about any advantages or disadvantages between the two, especially for cleaning/prepping different surfaces. Not intended for cleaning electronics, antiseptic or glug-glug reasons if I run out of beer, but for boatwork and other small repairs.

Beyond the usual boat materials, polyethylene hulls, Royalex/T-formex, composites made with Vinylester or epoxy or polyester gel coat, I use 90% isopropyl alcohol (or, once upon a time, higher-test lab alcohol) to clean other surfaces prior to repair; when cleaning and G/flexing separated soles to shoes and boots (yesterday), or fixing broken household doohickies (today, separating aluminum skin on French doors).

Even 90% isopropyl has yet to dissolve the pump gasket in my spray bottle, the additives in denatured alcohol might eat that gasket.

https://www.canoetripping.net/threa...d-on-my-denatured-alcohol.124771/#post-124792

I’ve done a lot of Googling and studying, sort of on my own.


(That PSA freaked me out as young guy. It wasn’t true)

But the choice of which, denatured or isopropyl, for what and why, is still clear as mud.

https://www.chemicals.co.uk/blog/isopropyl-alcohol-vs-denatured-alcohol

https://survivalfreedom.com/denatured-alcohol-vs-isopropyl-alcohol-for-cleaning/

I ask because I have a $5 off coupon for the local hardware that expires tomorrow, and I’ll be up that way.
 
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If you want to get rid of water before doing a repair, you are better off using denatured alcohol since isopropyl alcohol contains water. This can sometimes be important. An example is when preparing a three-layer poly or a Roylex canoe for repair that has exposed foam core. I usually clean the exposed core first using Dawn and warm water and a scrub brush to remove any oil or dirt. Then rinse well but small amounts of water will be left behind in the exposed cells of the core. The water will mix with denatured alcohol and a couple of applications of denatured alcohol will remove it. The alcohol will evaporate fairly quickly leaving a dry surface.
 
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I keep denatured on hand as a fuel and as a cleaner. I have isopropyl in the bathroom, but I don’t think it’s 90%. Incidentally, denatured worked to get dry erase marker out of my daughter’s new Easter dress.
 
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The only alcohol I use is 99% ethyl alcohol (it's denatured by leaving 1% methyl in from the distilling process) it burns excellently in my alcohol stoves and lamps and is an extremely good solvent, especially on organics, and even removes permanent marker, dry latex paint (but not cured), and most paint markers. I water it down to 70% for most general cleaning/first aid/disinfection tasks (a quick spray after paddling in contaminated waters), and 50% for deicing windshields and bug removal. If alcohol won't do the job I reach for the acetone...
 
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The only alcohol I use is 99% ethyl alcohol (it's denatured by leaving 1% methyl in from the distilling process) it burns excellently in my alcohol stoves and lamps and is an extremely good solvent, especially on organics, and even removes permanent marker, dry latex paint (but not cured), and most paint markers. I water it down to 70% for most general cleaning/first aid/disinfection tasks (a quick spray after paddling in contaminated waters), and 50% for deicing windshields and bug removal. If alcohol won't do the job I reach for the acetone...
Where are you finding 99% ethanol in Canada?
 
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Thanks. Usually they won't sell full strength ethanol without a lab licence. May have to give them a try. Pricey though compared to methanol especially when shipping is added. Likely there is booze tax in there somewhere. I have been buying 70% ethanol rubbing compound from the pharmacist and they'll only sell 1 small bottle at a a time
 
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it's perfectly legal to buy "denatured" ethyl alcohol, it's the drinkable stuff that's illegal without a license
 
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Y’all convinced me. It helped that I had a soon to expire True Value hardware $5 off coupon. There were a couple varieties, “For Fuel” and “For Glass”. I don’t use an alcohol stove and it’s time for spring cleaning; we have a lot of windows, so I bought the latter and will try some there.

Nowhere on the can does it list the chemical composition. A little post-purchase Google shows that the “For Glass” is 65-75% methanol, 20-30% Ethanol, 5% Isopropanol an 1% Methyl isobutyl ketone. Tastes yucky.

The 91% Isopropyl alcohol I mentioned came from Walmart, and lacking the methanol I know it doesn’t eat the pump gasket in my sprayer bottle.

P5160014 by Mike McCrea, on Flickr
 
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