Further thoughts on shellac

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H

HSteier

Well-known member
I've used shellac for almost all of my projects. I make up fresh batches of 2 pound cut for each project and use orange shellac flakes. I weigh the flakes and measure the alcohol in order to get consistent batches.  Currently I'm finishing a desk and I wanted to put a protective coat of polyurethane on the top, so I used dewaxed orange shellac. Despite using the same ratio (1 oz shellac flakes to 4 oz alcohol) it wouldn't all dissolve. I've never had this problem with plain (wax-containing) shellac. So I'm wondering, just how much of shellac is actually the wax which does not go into solution but just is suspended in the alcohol. If shellac is 1/3 wax, then a 2 pound cut of dewaxed shellac would have as much soluble solid as a 3 pound cut of plain shellac.
Does this explain my solubility problem?

Howard Steier
 
Howard, are you saying the shellac NEVER went into solution.  I use de-waxed shellac all the time and in various cuts.  Sometimes it seem it takes longer to dissolve but it always does.

Is it possible you have some contaminated or extremely old shellac?

I know for me with dewaxed blond shellac, it takes longer to go into solution.  Garnet seems better.

Ken
 
About 75% went into solution. The remainder did not over several days, even with intermittent shaking of the jar.
The flakes were bought off the shelf at my local Woodcraft.

Howard Steier
 
Howard,

It's likely that your problem of undesolved shellac is due to water contamination in your alcohol.  As you probably know already, alcohol is hydroscopic.  A container of partially used denatured alcohol can easily attract moisture, especially during the warmer humid days of summer.  In addition, any natural wax in shellac will usually desolve along with the shellac flakes and will look like a cloudy substance if the solution is undisturbed.  Hope this helps.

Mickey
 
Howard,

Shellac has been my finish of choice for over 20 years. I've never seen flakes remain undissolved (hard) after three days in alcohol. I'd agree with Mickey - that something is wrong with the alcohol, if that's the case. Likewise, if left undisturbed for a few hours, any wax should settle to the bottom and the shellac on top should be clear, not cloudy. If you have 25% of your flakes laying on the bottom in a gelatin-like state, then the flakes are going bad. Even though you just bought them, you don't know how old they were when they were repackaged, or how they were stored. If stored properly, darker shellac varieties will keep for years. I vacuum package mine and keep them in a metal cabinet in a cool area of my shop. I just mixed up some extra dark dewaxed stuff that I purchased in 1994 with no problems (somehow they got pushed to the back of my cabinet and I rediscovered them). Heat and dampness are real killers for shellac flakes. Dewaxed shellacs in general, but especially lighter varieties have a tendency to react with themselves and form polymers which are not soluble in alcohol.  If you've got gelled stuff on the bottom after three days, I'd say the flakes are bad. You should return them and buy somewhere else.

Another tip. Even if you screw the cap down tight on a can of alcohol, it will still absorb moisture. I found this out the hard way when I stocked up on 6 gallons of alcohol several years ago. By the time I got to the fourth gallon a couple of years later, it was cloudy and useless as a shellac solvent. I'm still using it to clean brushes and other chores. Now I never keep more than two gallons around.

Craig 
 
Craig, I think you hit the nail on the head. Not only does the stuff gel at the bottom of the jar, it also doesn't sand well when dried.
It's going back to the store.

Thanks,

Howard Steier
 
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