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From: John Thaden
Date: Mon, 25 Oct 1999 11:04:21 -0500
Subject: Alcohol, plastic and wood

>Bill Lifford wrote:
>>Does alcohol affect wood (swelling, etc) in the same way that water does?
>>Are some plastics dissolved by the alcohol?

I'm told the black plastic of some harps is ABS, and I know that some
mouthpieces are Teflon and nylon, and that some combs and perhaps some
reedplates are aluminum.
The following is from the Cole-Parmer Instrument Co. Catalog, but similar
information is available in appendices of catalogs of numerous suppliers of
plastic items:

Aluminum ABS PVC Teflon Epoxy Nylon
ethyl alcoh. B B C A A2 A
isopropyl a. B - A1 A2 A B1
acetone A D D A D A

A = No Effect - Excellent
B = Minor Effect - Good
C = Moderate Effect - Fair
D = Severe Effect - Not Recommended
- - = perhaps this means not tested.
footnotes
1 = Satisfactory to 72°F = 22.2°C
2 = Satisfactory to 120°F = 48.9°C

The Merch Index entry for ethyl alcohol (i.e. ethanol) says that the term
"alcohol" with no further modifiers generally refers to the ethanol-water
azeotrope (natural ratio after distillation) , which is 95.57% ethyl
alcohol (w/w). Analogously, "isopropyl alcohol", as used here by
Cole-Parmer probably refers to its azeotrope with water, which is 87.7%
isopropanol (w/w). Note that "rubbing alcohol" one purchases retail is
usually much lower % isopropanol. Similarly, 100 proof vodka, is only 50%
ethanol. These more dilute alcohols may have less severe effects on
harmonica parts than the azeotropes. This is my experience with 70% versus
95% ethanol regarding effects on polystyrene, which is the plastic of CD
and cassette jewel cases, by the way.

As for efficacy as a sanitizer, microbiologists commonly use 70% ethanol to
sanitize work areas and tools. I was taught 50-70% ethanol is actually
superior to 95% for killing bacteria. Some bacteria, and a host of fungi
are resistant to ethanol. CAUTION: Neither rubbing alcohol nor ethyl
alcohol sold in pharmacies, etc., are fit for drinking.

As for woods, while alcohols may certainly dissolve the natural oils, tars,
and pitches of various woods, these substances are not very volatile, so,
contrary to bp's assertion, they will not disappear with the alcohol as it
evaporates (neither do skin oils, an analogy he drew). But soluble wood
oils and tars certainly can be lost by dilution into the bulk alcohol
during soaking, or by being wicked into to a porous applicator pad if one
is used to apply the alcohol, or in drops of excess alcohol falling from
the wood. But the original method given in this thread for sanitizing wood
was to apply a fine spray of an alcohol/acetone mixture. This approach
makes sense to me as long as one doesn't then wipe the item dry or set it
on a porous surface.

- -John Thaden, Molecular Geneticist

Bill Price wrote:
>I used to raise the grain on wood which I was finishing by wetting it, then
>sand the raised grain smooth. Alcohol will do that, but to a lesser extent
>and it evaporates faster, and when it does, it can take some of the oils
>from the wood with it.
>
>I've never found a plastic dissolved by alcohol . . . .

fjm wrote:
>Yes alcohol will melt several types of plastic that I am aware of, ABS
>the common harmonica comb plastic is unaffected by alcohol. I remember
>using alcohol to clean vinyl records and the stylus to my turntable
>worked fine until one day the bottle tipped and spilled its contnents
>onto my cassette tape collection. It welded about 10 of the cases shut
>and fogged all of the plastic. The tape and the cassettes survived it
>just fine. fjm



John Thaden
Little Rock, Arkansas, USA
http://www.flash.net/~jjthaden