Official Luthiers Forum!

Alcohol absorbs moisture from the air as soon as the bottle is opened. The 'aziotropic' solution, which has the lowest boiling point, is 95% alcohol and 5% water, and that's what it will go to as soon as you expose it to air. That's why 190 proof, 95% alcohol, is the standard; its the best you can get through regular distillation.

In the old days they used to add benzene, which binds more strongly to the water and allows for the production of a more pure alcohol. It always had a little benzene in it, though, and they stopped doing it that way when they found that benzene id carcinogenic. Now I'm told they remove the last of the water by putting in burned ('unslaked') lime. This reacts with the water to form an insoluble product that settles, or can be filtered, out.

You don't need to get all of the water out, and can't anyway. As I say, I've found that the 70% ethyl that I get at the drug store, which has (probably) 5% water, and some acetone, works fine.

JF, there was no internet during my college days (and not for many years after).
Yes it is expensive, but the Everclear at the local Bevmo here in CA is 120 proof and costs $49 for 1.75 liter. There is a way to strip some of the water out with salt (the alchohol floats on top of the saline solution) but it makes my drinks taste funny.

70% is 140 proof if I'm not mistaken right? People claim that the 150 Proof Everclear is not good enough for shellac finish. Am I missing something? I mean I know obviously it works for you so maybe my understanding of proof is wrong.

Look at the rest of the sentence: part of the mixture is acetone, which doesn't interfere with dissolving alcohol. I've been using a mix of 2 parts acetone to 1 part 2# cut shellac for FP for some time. It flashes off so fast that you can actually build it quicker than straight 2# cut. Certainly if the mix was just water and alcohol it would be problematic, but this is not.

As a bonus I found a case where it works even better than plain alcohol. When I first tried the drugstore stuff I used some seedlac that somebody had given me. As you may know, seedlac is unrefined, and can contain all sorts of stuff. Usually the 'tea bag' will filter out the dirt and wax, and give a reasonably clear solution, but this stuff always looked 'dirty', and no amount of filtering would clear it. I figured, if it didn't work it was no loss. What happened was that the solution stratified into two layers; a clear top layer of red shellac solution, and an opaque red layer under it. I suspect that the the red layer is a solution of red lac dye in water. I have not tried adding more water to see if any more color would come out. It's possible to decant the shellac layer and that works fine, although, obviously, it's best on a dark wood. I've always likes seedlac as a finish; it does tend to be darker than most of the refined shellacs, but it's also more durable. Usually they wash out the red dye (which is much more valuable than the resin), but apparently in this case they didn't

"Look at the rest of the sentence: part of the mixture is acetone, which doesn't interfere with dissolving alcohol. I've been using a mix of 2 parts acetone to 1 part 2# cut shellac for FP for some time. It flashes off so fast that you can actually build it quicker than straight 2# cut. Certainly if the mix was just water and alcohol it would be problematic, but this is not."

I thought the reason people were buying high dollar ethanol was because they wanted to avoid large doses of other chemicals in the F.P.. I know the body produces acetone naturally but not in very large amounts.

I think different folks have different goals.

Truer words...

_________________
For the times they are a changin'

- Bob Dylan

I received the gallon of 190 proof denatured ethyl alcohol from Best Cleaning Supply. When I revisited their website they have discontinued it. It was priced at $33 a gallon with free delivery, so wasn't too bad a deal compared to other sources of relatively pure ethanol. Even relatively innocuous solvents are getting hard to get.