TromboneChat

I heard from a friend, who's dad was a musician, that he used denatured alcohol instead of rubbing alcohol on his instruments to remove oil residue, because he said rubbing alcohol leaves a film on your instrument that could be harmful or prevent it from being completely clean. Is this true? I use rubbing alcohol quite regularly on my lacquered brass trombone and have never had any problems.

Both have additives in the alcohol that make the alcohol inedible and thus ineligible to liquor laws and taxes. The particular additives varies by the specific formulation, so I don't see how a "denatured" alcohol is necessarily free of leaving a film behind. Maybe there's a particular one your friend gets?

I suspect it depends on what additives are used; as Andrew pointed out, neither is pure alcohol.

Back when I worked as a metallurgist, we'd rinse samples with methanol so they'd dry without residue. Harder to get that rubbing or denatured alcohol. One time we ran out and tried using drug store rubbing alcohol; it left the samples cloudy.

Denatured alcohol SHOULD be only ethanol, with methanol added as the substance that makes it inedible, as methanol is much more poisonous than ethanol.

Always rinse with water after alcohol anyway.

https://en.wikipedia.org/wiki/Denatured ... rmulations

For exactly what is in the stuff, it seems to matter where in the world you live.

Just to put a few things in order:

Rubbing alcohol is a mixture of isopropyl alcohol (CH3-CHOH-CH3) and water. Some blends are 70 percent alcohol and some are 90 percent alcohol. The water is not necessarily pure. Isopropyl alcohol is poisonous and should not be ingested.

Denatured alcohol is ethanol (CH3-CH2OH) with some additives. Ethanol is the active ingredient in alcoholic beverages and in moderation is not poisonous. The additives in denatured alcohol render it very toxic and it should not be ingested.

Methyl Alcohol (also called "wood alcohol") (CH3OH) is poisonous. Usually sold as 100 percent, but there may be tramp materials.

Which leaves the least residue? You'd have to test. FWIW, I usually use the 90% isopropyl alcohol since it seems to be easier to find here.

For those interested, I found this handy document with more details:

http://online.personalcarecouncil.org/c ... /PR273.PDF

For example, the alcohol used by my handy electric shaver cleaner is "SD Alcohol 40-B", which is apparently pretty common. Any cosmetic alcohol should have a formulation like this somewhere on its label. That should make figuring out the odds of any particular alcohol leaving a residue a bit easier.

Most of the formulae Andrew has listed will leave a residue on evaporation. There are three exceptions: 3-A, 30, and 40-C. Even diethyl phthalate, which is a liquid, is not likely to evaporate fully. And most of the other dentaturants are salts and hence solids.

No pure alcohol, blend of pure alcohols or blend of pure alcohol and pure water will leave a residue. The only one I know that is available pure (without blending with other alcohols or water) to the general public is methanol, aka wood alcohol. Most alcohol concoctions will list the ingredients - either right on the bottle - or on the WHMIS listing.