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Alcohol cautions

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Alcohol cautions

Postby Steve Sawyer » Sun Oct 08, 2017 3:11 pm

I'm sure some of the old hands around here are aware of this, but I was not, and almost created a disaster for myself. I'm posting this info for the benefit of the other noobs who might make a similar mistake.

I hadn't considered for a moment that denatured alcohol was a solvent for nitrocellulose lacquer, and got a nasty surprise when I swiped an alcohol-moistened cloth across a nitro finish! Fortunately I didn't do a lot of damage (I'm in the sanding stages, so what damage was done was removed in that process). However, I did a bit of further experimenting and verified that fully cured nitro can react to denatured alcohol the same as it would to lacquer thinner - the finish was immediately softened and liquefied. This also explained another phenomenon I'd observed recently. I use alcohol (per 3M's recommendation) to clean a surface prior to attaching those "command" removable wall hooks that 3M makes. When using it on a semi-gloss painted wall recently, I was surprised that the alcohol softened the paint, and some of it came off on the paper towel I was using.

On digging further into this, I discovered the following.

The MSDS for my every-day denatured alcohol (Klean-Strip) shows the following:

Ethanol - 45-50%
Methanol - 45-50%
Methyl Isobutyl Ketone - 1-4%

I was surprised to see methanol at such a high percentage, as I'm sure a much smaller proportion would be sufficient to make the product undrinkable, but given the incentives to add ethanol to motor fuel, it's probably cheaper to use more methyl alcohol in the mix. But I was suspicious of that Methyl Isobutyl Ketone. Some research revealed that this is a solvent for "gums, resins, paints, varnishes, lacquers and nitrocellulose". I suspected this additive was the culprit in dissolving nitro lacquer.

I also have a couple of cans of denatured alcohol that someone somewhere informed me was a superior solvent for dissolving shellac flakes. I pulled up the MSDS for this product (Klean-Strip Green):

Ethanol - 80-90%
Methanol < 5%
Ethyl Acetate - 1.5%

This was more like it, but I looked up Ethyl Acetate and found this:

"Ethyl acetate is used primarily as a solvent and diluent, being favored because of its low cost, low toxicity, and agreeable odor. For example, it is commonly used to clean circuit boards and in some nail varnish removers (acetone and acetonitrile are also used). Coffee beans and tea leaves are decaffeinated with this solvent.[6] It is also used in paints as an activator or hardener...Ethyl acetate is present in confectionery, perfumes, and fruits."

It was also cited as being an important flavor component in wine.

I was concerned that this too might be problematic. A quick test by placing a few drops of this onto some cured nitro showed that it did NOT immediately attack the finish as did the stuff with the methyl isobutyl ketone. I then placed another drop onto a fresh area of the cured lacquer, and allowed it to sit undisturbed for two minutes. On wiping it off, the finish appeared undamaged, retaining its original gloss. However, the finish was softened by the alcohol - a fingernail could leave an impression in the surface.

I don't have a can of Behkol to experiment with, but the MSDS for that product cites 81-90% ethanol, plus isobutyl alcohol, isopropanol and some small concentration (1-10%) of a non-alcohol solvent (Propyl Acetate) that may or may not cause a problem with nitro. Note that Behkol contains NO methanol!

One last point - the ethyl acetate is rated as very low toxicity, whereas the methyl isobutyl ketone seems to be much nastier stuff. Needless to say, I replaced the alcohol in the squirt-bottle I keep in the rack above my workbench with the Klean-Strip Green stuff since that's my source for a quick shot of alcohol solvent for cleaning.

If anyone can add to this (or correct any errors in my research) please do so!

---
Edit to add a link to the place I got the advice on denatured alcohols:
https://www.shellac.net/alcohol.html


Alcohol.JPG
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Re: Alcohol cautions

Postby Barry Daniels » Sun Oct 08, 2017 4:08 pm

Alcohol is usually one component of lacquer thinner. I sometimes use straight alcohol to thin lacquer or use to clean touchup brushes.

I keep a squirt bottle of orderless mineral spirits to do cleanup. It works on most everything and it does NOT affect lacquer finishes or plastics. Alcohol will also soften most plastic/vinyl surfaces.
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Re: Alcohol cautions

Postby Steve Sawyer » Sun Oct 08, 2017 5:23 pm

Barry Daniels wrote:I keep a squirt bottle of orderless mineral spirits to do cleanup. It works on most everything and it does NOT affect lacquer finishes or plastics. Alcohol will also soften most plastic/vinyl surfaces.


Along with the alcohol, I too keep a squirt bottle of odorless mineral spirits in the rack, plus a bottle of naphtha - along with a squirt bottle of Goo-Gone, a small can of WD-40, a small can of 3-in-1 oil - I have it all covered, as long as I use the right solvent for the job! I'll have to be more careful with the alcohol. Wouldn't have guessed that it would also attack any plastics!

Oh - I was curious as to whether the "purer" denatured alcohol would clean up uncured epoxy as well as the other stuff, and it appears to do just as well.
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Re: Alcohol cautions

Postby Alan Carruth » Mon Oct 09, 2017 2:47 pm

Recently I've found 'Denatured Ethyl Alcohol' at the local drug store. They don't always have it, but when they do I get some. It's listed as being 70% ethyl alcohol. The inactive ingredients are, in order, Acetone, denatonium benzoate, methyl isobutyl ketone, and water. We know, of course, that any open container of ethyl alcohol will contain 5% water. I wonder if it's more than 5% MIK? I know this stuff tastes very bitter if you get it on you hands and touch them to your mouth. I have yet to try it as a French polish solvent. I'm already using denatured alcohol and acetone mix for that anyway, so this might be better. It is certainly cheaper than grain alcohol from the liquor store!
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Re: Alcohol cautions

Postby Simon Magennis » Tue Oct 10, 2017 4:46 pm

Steve Sawyer wrote:The MSDS for my every-day denatured alcohol (Klean-Strip) shows the following:

Ethanol - 45-50%
Methanol - 45-50%
Methyl Isobutyl Ketone - 1-4%

….


I am very surprised at that.

I don't think de-natured alcohol in Europe today contains any methanol and certainly nothing like that volume. When it was included in the past it was below 5% as far as I am aware. Ever in my school days in the dim distant past we were warned about the dangers of methanol.
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Re: Alcohol cautions

Postby Dan Smith » Tue Oct 10, 2017 5:50 pm

I'll add that the Clean Strip will easily take the shine off of polyurethane.
Ever-body was kung fu fight-in,
Them kids was fast as light-nin.
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