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Alcohol Disolve Lacquer?!!!

Rich14's picture

Has anyone ever had this happen?

I have a can of "Denatured Alcohol." I bought it at Wal-Mart (my first mistake). The brand is Crown, PSC, Packaging Services Co., Inc, Pearland, Texas, 77581,

I'm refinishing some guitars. Initially, I used Qualasole, a padding lacquer, I know to contain nitrocellulose lacquer and a number of solvents and lubricants in a proprietary formula. I had partially finished one instrument and had an "accident." I was using a non-woven pad, which is actually a paper product. The Qualasole film was still soft, I absent-mindedly hesitated in my padding motion, the pad "caught" in the lacquer film and a hunk of paper fibers ripped right out of the pad and embedded themselves deeply in the film.

In my heart I knew I would have to take the lacquer down almost to bare wood to get the mess out, but I tried to "finesse" it and "pull" the fibers out with gentle steel wooling. It worked to an extent. I decided to try wiping with alcohol to "wet" the fibers, thinking they might further let go.

I have used alcohol many times on guitars to clean off embeded skin oils, without any damage to the finish, ever.

I have used Qualasole routinely for over 20 years, and pretty much know its characteristics, but I'm not sure if I ever actually applied alcohol over it. Any surface I apply Qualasole to is then pretty much a "virgin" lacquer surface, not needing any cleaning from that point.

I wiped an alcohol-damp pad over the Qualasole film and was horrified to feel and see the alcohol take the finish off like I was using lacquer thinner! Luckily I didn't destroy too wide an area. I let it dry, carefully sanded with 400 grit, then steel wooled it, and gradually repaired the area. All the while, puzzled that alcohol could do that to Qualasole. I figured it must contain shellac in addition to lacquer, and that's why it wiped off like that.

Then I had to make much more extensive finish repairs to several other instruments, requiring full-blown lacquer spraying. The work required me to mask off large areas with low-tack masking tape as I went. After I removed the tape from the top of one guitar, I saw some gummy adhesive from the tape.

I reached for the same alcohol to remove it. I don't know why I reached for alcohol. I have removed adhesive from lacquer surfaces a million times before with mineral spirits. Mineral spirits is absolutely, perfectly safe on lacquer finishes.

I wiped the alcohol on the guitar, and, you guesed it - the finish came right off!

This was pure, dry, nitrocellulose lacquer. No shellac on that guitar whatsoever. That instrument had 3 days worth of my meticulous spray finish on it.

I found the MSDS on the Internet for this brew of devil's denatured alcohol. Here's the part describing the contents:

CONTAINS: 65-75% METHANOL (67-56-1)[200-659-6],
20-30% ETHANOL (64-17-5)[200-578-6],
< 10% ISOPROPANOL (67-63-0)[200-661-7],
< 10% METHYL ISOBUTYL KETONE (108-10-1)[203-550-1]

Look at that last ingredient. Methyl isobutyl ketone! LACQUER SOLVENT! Very potent stuff.

What in heaven's name is THAT doing in there? Is this a denaturing agent?! The stuff is already 75% methanol. What further denaturing is needed?

I guess we have to read MSDS information now before using solvents for finishing, and be chemists, as well.

The can lists "cooking fuel" as one of its uses! With methyl isobutyl ketone?! I know how to handle an alcohol flame. But alcohol and ketones are the stuff of Meth labs and violent explosions.


SteveSchoene's picture

(post #111403, reply #1 of 9)

If you check down near the end of the MSDS for Qualasole you will see "Natural Resin" with no CAS number given and a bit more than 8% content.  I'd be willing to bet a big chunk of that is shellac, and at 8% it's most of the 9% by weight or 12% by volume solids content.  Nitrocellulose does have a CAS but and is listed among the hazardous chemicals with 1-10% content.  Qualasole's principal solvent is ethanol, followed by isopropanol, with a little methanol thrown it.  Due to the way these percentages are calculated the numbers don't quite add up, but padding lacquers generally are mostly shellac. 

By the way, the MSDS is easy to find on the Rockler site, not so much on Behlen's. 

I agree that a product labeled Denatured Alcohol shouldn't be more than 2/3rds. something besides ethanol, especially when the something else is as hazardous to breath or ingest as methanol, not to mention the ketone.  I suppose it could be the same problem from almost any source, particularly the "low cost" stores, which would include all of the borg, and likely most standard paint stores. 

Edited 10/7/2007 8:35 pm ET by SteveSchoene

Test your finish on scrap, FIRST, or risk having to scrap your finish.

saschafer's picture

(post #111403, reply #2 of 9)

Methyl isobutyl ketone is listed as a denaturant in several of the formulas in 27 CFR 21, which is the U.S. regulation covering denatured alcohol, so that part's officially okay. What doesn't make sense, however, is the fact that the Crown product lists methanol as the majority component. None of the formulas for denatured alcohol in 27 CFR 21 have more than 10% methanol.



HowardAcheson's picture

(post #111403, reply #3 of 9)

Here is a quote from an online encyclopedia.

"Denatured alcohol is ethanol which has been rendered toxic or otherwise undrinkable, and in some cases dyed. It is used for purposes such as fuel for spirit burners and camping stoves, and as a solvent. Traditionally, the main additive was 10% methanol, which gave rise to methylated spirits. There are diverse industrial uses for ethanol, and therefore literally hundreds of recipes for denaturing ethanol. Typical additives are methanol, isopropanol, methyl ethyl ketone, methyl isobutyl ketone, denatonium,...."

As you can see, the components listed on the product you bought are the same as described above.

Also, as ethanol is increasingly used as a auto fuel, it is getting quite a bit more expensive. It may be cheaper to make denatured alcohol using more methanol than ethanol.

Rich14's picture

(post #111403, reply #4 of 9)

Guys, I have no problem with the methanol content in this stuff, and I guess I've just been lucky 'till now, getting away using alcohol that didn't harm lacquer. But I'll have to be very careful from now on about my sources for denatured alcohol. Denature it any way you want Mr. Manufacturer, using methanol and organic solvents. Just don't put lacquer solvents in there, please.

mwenz's picture

(post #111403, reply #5 of 9)

Whatever Qualasole really is, it contains a sig. amount of shellac--and denatured alcohol. Just add a bit of DA, it will mix right in just fine.

No idea what Behlen really did to concoct the stuff, but I use it every day. It's a good finish--but don't try to touch it with DA. fwiw, I use Acetone to clean up on and around Qualasole.

Take care, Mike

brucet999's picture

(post #111403, reply #6 of 9)

Denatured alcohol has always been a blend of ethanol (usually 85%) and one or more oxygenated solvents including methanol, isopropanol, ketones and/or acetates (usually butyl or propyl acetate)but never any hydrocarbons.

Ketones and acetates are common lacquer thinner components and methanol is a major component in paint removers.

What they sold you cannot properly be called denatured alcohol. It should be labeled denatured methanol.

saschafer's picture

(post #111403, reply #8 of 9)

"Denatured alcohol has always been a blend of ethanol (usually 85%) and one or more oxygenated solvents including methanol, isopropanol, ketones and/or acetates (usually butyl or propyl acetate)but never any hydrocarbons."

That's not quite true. Some of the denaturation formulas specify kerosene, or even gasoline (!) as denaturants. However, those formulas are for fuel, rather than solvent, use.



SteveSchoene's picture

(post #111403, reply #7 of 9)

I would have some concern about methanol toxicity.  It's OSHA threshholds are well below those of ethanol or isopropanol.  Methanol is also a HAPs (Hazardous Air Pollutant) for those that fall under those regulations, while ethanol is not.  Methanol is the stuff that makes you blind, (usually temporarily).

The Crown "Denatured Alcohol" as described, doesn't appear to fall into any of the denatured alcohol formulas in the US regulation.  These DO NOT include any language like "add at least 10 gallons of methanol..." but DO include prescriptions to add certain amounts of denaturants to alcohol of at least 160 proof, or at least 185 proof.  The loophole may be that "Denatured Alcohol" as a term may not be limited to items that fall in the formulas for completely denatured alcohol or specially denatured alcohol that are given in the regulations.  But it still looks pretty darn close to the edge of misleading packaging to me. 

One interesting tidbit of information I uncovered while looking on line about this was that ethanol blocks some of the harm that methanol might do on the body, so a good stiff drink might be recommended after finishing a project with shellac thinned with such high methanol "denatured alcohol".  As long as the "after" part is observed sounds like a good idea anyway. 

Test your finish on scrap, FIRST, or risk having to scrap your finish.

Hastings's picture

(post #111403, reply #9 of 9)

Sorry to hear about your finishing problems. It's very frustrating when all the previous hard work gets wasted and you have to go back to the beginning.

Not to hi-jack the thread, or digress (too much), but I was curious if your Hammer had arrived? Is it all up and running? Are you pleased with it? Did you have any difficulty with calibration?