Shellac: soft when cured

I checked my jar of shellac this afternoon.... I put a few blobs on the side of a metal clamp , it was a warm/hot day.....

after half an hour.. and again after an hour.. it still felt softish... I could scrape my nail through it...

should that dry to a harder flake on metal?....

 

Sounds like yours has gotten old, and probably shouldn't be used as a topcoat any more.

You can dilute it down and still use it as a sealer, but probably best just to pitch it.

The easiest way to get rid of/clean up old shellac is with some household ammonia. Ammonia destroys the adhesive properties, and the shellac will turn purplish/reddish and can then be poured down the drain cleanly and safely.

As an aside this was the original use for shellac - neutralized with a strong base it forms a natural pigment.

 

No such thing if you wait a sufficient time between applications. I use canned clear Shellac in de-waxed Seal Coat then on top of that several coats of canned clear Shellac cut 1-1 with denatured alcohol. I usually wait at least 3-4 hours between applications and sand with a 400 grit foam rubber sanding pad between coats. Then after 24 hours of the final coat (usually 6 to 8) apply a few coats of citrus wax applied with 0000 steel wool buffing with a clean well used Tee Shirt after each coat.

I will at times forgo the wax and apply a couple coats of wipe on Satin Poly waiting at least 24 hours between coats. That is the nice thing about Shellac, it will adhere to about anything, even itself if applied properly.

No matter how many coats of Shellac you apply it will never get as hard as Bakelite.

 

I apply the wax with the 0000 steel wool, let it set for a few minutes then buff it with the tee shirt and do that process another 3 or 4 times.

Have never tried or even thought of polishing compound anywhere in the finishing process.

The link posted is exactly the wax I use on my natural grain wood and use the natural wax for all my projects.

 

We'd have to agree on a method of testing harness for it to really matter, and bakelite was never something that got laid down in a thin layer like a shellac finish anyway. So any testing would be rather irrelevant anyway.

Bakelite was developed as a substitute for shellac being used as a molded plastic, not a wood finish.

Shellac buttons may not be technically "as" hard as bakelite, (but even that depends on the bakelite - much was reinforced with paper or cloth) but they are darn hard. Hard enough that you would not appreciate being hit by one. Easily hard enough to use as guitar or amp knobs.

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Waxing your finish is a good way to get a nice lustre, and fill any micro sized scratches. Being quite thin, and having minimal adhesion, it's effect is primarily cosmetic, and it really won't offer any protection from normal wear/sweat/body oils, etc.

But that should not be a major concern anyway. People used to finish hardwood floors with shellac, so it does have some durability.

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You can use modern polishing compounds on shellac - with extreme caution.

Most modern compounds need to be used with a mechanical buffing device in order to perform well. And that is the danger.

Shellac does not tolerate heat well at all. If you are not very careful you can easily overheat the finish, and it will turn into a soft, gummy mess.

At that point your only option is to scrape it off and refinish. The damaged area, having been chemically altered by the excess heating, will not respond well to spiriting off, or glazing, or any other padding type technique.

 

Shellac, whether dissolved in alcohol, or flake on the shelf has a lifespan. In solution it is about a year maximum. Flake, if stored in a cool, dark, dry place, can remain good for years. Commercially stabilized solution are supposed to last for three years, but I'm skeptical.

Any time you intend to use a shellac solution you should brush a few coats onto a piece of ceramic, or glass, then allow it to dry overnight.

The next day the resulting dry film should be hard, clear, and fairly brittle, a nail tip should scratch the surface, and when you attempt to peel up the edge it should break off in chips/flakes.

If it doesn't do this - if it is not dry, or it bends/dents instead of breaking - then the shellac is not suitable for use as a topcoat.

Since most everything sticks to shellac it still can be thinned out and used as a sealer coat, say for example, in between staining and grain filling. Or for sealing off oily/refinished wood prior to shooting lacquer.

Comparing non-dewaxed to dewaxed is difficult, mainly because the volume of wax can vary wildly. A heavy cut solution made from seedlac can end up being about half wax/wood chip/bug detritus. A non-dewaxed amber much less so.

In my experience the biggest predictor of durability is color. Darker colors seem to resist wear better. But even the finest platina should still dry hard.

 

Not sure what you mean by a synthetic sealant.

Shellac itself is considered a near all purpose sealant, meaning it commonly is used to form a suitable barrier between two otherwise incompatible layers.

There are limits though, I've generally avoided using enamels on or under shellac.

If you are talking about putting a protective topcoat over shellac (like an acrylic or lacquer) then yes that can be done, but if the undercoating of shellac is still soft you will only further delay/impede any more drying or hardness and that may lead to problems.

A better description of what you intend/are trying to accomplish might be helpful.