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Question 70% isopropyl alcohol

Discussion in 'General Chit-Chat' started by Geneva Olson, Mar 9, 2020.

  1. signmania

    signmania Owner

    May 1, 2010
    Cedar Rapids, Iowa
    I've never had a problem with denatured (I get it on sale at Menard's). If the vehicle is relatively clean I go over the surface with Sparkle (no ammonia in it!) and then finish with denatured. I do wipe down the surface again with a clean dry towel to make sure there is no haze left behind. I've never had a problem in 30 years.
  2. signbrad

    signbrad Member

    Jun 15, 2014
    Kansas City
    Back in the day, many shops used denatured alcohol as it was readily available and inexpensive. The main use for it in all the shops where I worked was as a wipe for plastic prior to back-spraying with translucent sign paints. We always cut the alcohol with water or it would streak. I usually cut it 2 to 1 which is roughly the same concentration as rubbing alcohol. Standard practice was to wipe only with a chamois to avoid introducing static which created havoc when spraying (and even when hand lettering). But I eventually switched to the synthetic chamois substitutes that came in a plastic tube at the auto parts store. They seemed to work as well and the tube kept them from drying out. Laundered them periodically or they would smell pretty bad. Conversely, paper towels and shop rags always created static.

    The three commonest alcohols used are methanol, ethanol and isopropanol. All are simple hydrocarbon molecules, but methanol is the simplest and cheapest. It is, however, highly toxic. Its main use is as fuel for race cars. It is also not uncommon to add a tiny amount of methanol to adulterate ethanol to make it "denatured." Without adding some kind of toxic chemical to ethanol, you would be able to drink it. All three of these alcohols are miscible in water, though only methanol is miscible in both water and oil. Alcohols are used as solvents in inks, paints, adhesives and many other things. Mixed with water, alcohol is an excellent cleaner that is not harsh. Used in a mix with some of the lacquer thinners (toluene, xylene, etc.), it becomes a decent paint stripper. The old T4000 Griplflex paint stripper for plastic faces was basically an alcohol mix.

    None of which, of course, answers Chuck's question.

    Brad in Kansas City
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  3. TimToad

    TimToad Very Active Member

    Jun 13, 2013
    If we can't find the 70% or 91% at our local Big Lots! or other source, our Denco Sales has the 99.50% isopropanol for $75 per gallon, which is 200% more than it was not that long ago.

    When forced to go that route, we make a couple different concentrations out of it and can usually stretch it to several gallons of liquid in three or four different strengths.
  4. rjssigns

    rjssigns Major Contributor

    Jun 4, 2007
    Home Office
    We have 99% isopropyl wipes in the lab. Goes something like this: Bring container as close as possible to what you need to clean. Pull wipe from container and aah crap its dry, grab another and move fast ahhh crap. End up grabbing the squirt bottle and KimWipes.
  5. Mike Paul

    Mike Paul Major Contributor

    Dec 30, 2003
    I usually buy 91% Iso by the case to prep vehicles but you cant find any grade isopropyl around here in the stores.
    Just bought 10 gallons of Medical grade 99% Iso from a local janitorial supply store. Runs about $17 per gallon.
  6. DustyCanine

    DustyCanine Multimedia Specialist

    Nov 14, 2017
    Best way is to get a gallon at home depot.

    should be near the paint
  7. Mr. Signboy

    Mr. Signboy New Member

    Feb 5, 2020
    Seattle, WA
    I buy mine from ULINE, they have 70% and 99%. Most of the small sizes are sold out but you can still get 5 gal cans, which is a better deal anyway.
    • Agree Agree x 1
  8. Jeremiah

    Jeremiah Member

    May 7, 2019
    I use Denatured Alcohol. This summer I was in a hurry, and got it on my skin. By the next morning, my hands hurt and they puffed up to double sized fingers. Almost could not work. It took a bit over 24 hours to go back down in size. I now aways wear rubber gloves when I prep a sign surface .

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