Official Luthiers Forum!

I have some shellac from flakes and Everclear that needs to be thinned. I am out of Everclear. Is it ok to just add denatured instead?

yes
Mike

_________________
Mike Collins

Many people use denatured alcohol (myself included) to dissolve shellac flakes. It won't hurt the shellac, but some feel it might hurt you. If you can find Jasco green denatured alcohol it may have a higher percentage of drinking alcohol (ethanol) than other denatured alcohols:
https://jasco-help.com/jasco-green/jasc ... d-alcohol/

Some people thin shellac with acetone. I have never done that. Acetone occurs naturally in the human body as a byproduct of metabolism so some may feel it is less of a problem than other thinners. I'm not sure I believe that, but a small amount might be O.K..

I've been using a mix of two parts acetone to one part 2# cut shellac for some time. You need to have good ventilation with this stuff! It flashes off very fast, and so builds a lot quicker than you might think.

I use Isopropyl alcohol from Kroger. Works! Doesn't give me a headache.

_________________
Why be normal?

Isopropyl may have water in it-even if its 90%


Mike

_________________
Mike Collins

I buy lab grade 99.9% 5 litres <$30

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Someone wrote a great article on the subject of alcohol solvents for shellac a while back in American Lutherie. Oh wait, it was me:

Mottola, R.M. "About Alcohols Used as Solvents in French Polishing" American Lutherie #105, 2011, p. 38.

Full text of the article is available here:

https://www.liutaiomottola.com/PrevPubs/Alcohol/alcohol.htm

_________________
R.M. Mottola
LiutaioMottola.com

Author of the books Building the Steel String Acoustic Guitar and Mottola's Cyclopedic Dictionary of Lutherie Terms.

That is a very good article for French polishers (or anyone who uses denatured alcohol) to read. If you consider the lower limit of ethanol percentage listed on the MSDS you can get an idea of the maximum amount of denaturants added, although the particular mix may vary from batch to batch.
"Green" labeled denatured alcohols usually contain a higher percentage of ethanol but check the MSDS.

I’ve always felt there’s only one appropriate solvent, if you really intend to do some Polish-ing.

Pure (200 proof) Ethyl alcohol absorbs water from the air as soon as you open the bottle, and then it's 190 proof. Here in the USA, as a legacy of Prohibition, we pay a very high tax on 190 proof alcohol. 200 proof requires special permits, but it's not expensive once you have the paperwork, I'm told.

I've had problems in the past with hardware store denatured alcohol. They seem to change the formula depending on what denaturants are available and cheap, so the outcome can be erratic in French polishing. Before the pandemic I was getting 70% Ethyl rubbing alcohol at the drug store. The ingredients are alcohol, acetone, denatonium benzoate, methyl isobutyl ketone and water. There's not enough water in it to affect the way it works (I suspect it's the natural 5%), and it basically just tastes terrible. Since it's listed under USP I gather that it's not as harmful as some of the other denaturants (nicotine, gasoline, etc.) that can be used, and if it's available it will be what it says it is. The problem, of course, is that all of the 'industrial' ethyl alcohol got diverted to hand sanitizer, and now to stretch out oil supplies in gasoline; I haven't seen it in the store for several years. Drat.