shellac question -- very slow to fully harden

[neilc]

Hi, I've started working with shellac recently and am still learning about how it works. The only problem I have at this point is that my shellac finishes are staying a little bit soft for a long time -- several weeks up to a couple of months depending on the thickness of the shellac. It dries quickly and gets somewhat hard, but sitting an object on it or pressing with a fingernail will result in an indentation. A moderately heavy object left sitting for a week or so will push its way down to bare wood.

I started with the zinsser shellac (and the exp date was ok) but after doing some reading here I switched to shellac flakes purchased online. Both types of shellac are giving me exactly the same problem. I have been using denatured alcohol in a blue and red gallon can from home depot, and have had the same problem with several different containters of that, so I have ruled out the possiblity of a 'bad batch' of alcohol. Also I have used the shellac on several projects and at a variety of temperatures and have had the same problem consistently.

So my conclusion is that it has to be either a tecnhique issue or the denatured alcohol I am using is not good enough. Or maybe it's another problem that I haven't considered. What should I do differently?

Thank you in advance for any advice.

-Neil Covington

[J T]

Fri, Jan 19, 2007, 9:53am (EST-3) [e-mail] (neilc) doth woefully query: Hi, What should I do differently?

You're stirring clockwise, rather than counter-clockwise, aren't you? That's the whole problem.

Way too many details lacking to give a viable response to your query.

JOAT A problem adequately stated is a problem well on its way to being solved.

- R. Buckminster Fuller

[Nova]

How long are you waiting between coats?

[nailshooter41]

More details would be a good thing. But as a shot in the semi-dark, go to a good paint store and buy anhydrous alcohol. It is supposed to be 99.9% water free, and certainly works the best.

On the other hand, shellac is not a hard finish. If you are looking for something like "bar top" hard or even some of the polys, you need to switch to another product.

With that in mind, my personal experience is that when it stays soft for a while it was put on too thick, or the shellac itself was too thick for your application. I have also found that shellac stays a little more pliable in our South Texas heat than I would like, but behaves nicely when temps go into the Fall range.

Robert

[Nova]

Dewaxed shellac has excellent hardness. It sounds like your using either shellac containing wax or it's old.

[Lew Hodgett]

neilc wrote: > The only problem I have at this point is that my shellac > finishes are staying a little bit soft for a long time -- several weeks > up to a couple of months depending on the thickness of the shellac.

Like you, I'm on a learning curve with shellac, so can relate to your problem.

If you look at the Zinsser shellac container, you will notice that it contains 3# shellac and they suggest cutting it to 2# shellac before applying.

For me, that works after a fashion.

I have found that if you cut it to 1# shellac, I get better results, especially when applying additional coats.

As a result, have started using equal parts of 3# shellac and denatured alcohol, which yields slightly less than 1# shellac.

This mix is providing good results.

My motto has become, "If in doubt, add more alcohol".

HTH

Lew

[Nova]

Zinsser's "Bullseye" shellac is high in wax content. Decant the wax out of the mix or try their "SealCoat" which is dewaxed.

[Lew Hodgett]

Are you suggesting that dewaxed shellac provides a better finish, especially if multiple coats are used?

Lew

[Andy Dingley]

I wouldn't go _quite_ that far for simple finishes, but it's certainly a lot easier to screw up a shellac finish with a waxy shellac than a dewaxed shellac.

If it's taking really long to harden though, I'd replace it. We can't see what the real problem is, but old shellac that refuses to dry is such a common problem that it's certainly worth a try.

[Dave Hall]

SNIP of a shellac discussion

I know a number of people with that same life motto....

Dave Hall

[Old guy]

I'm still using the canned stuff, but have had good luck. I do dilute it about 50/50 with alcohol, and it almost flash dries. I can get in about 4 coats in an afternoon.

I'd try a stronger dilution, and see if that helps. Means more coats of course.

Old Guy.

[Father Haskell]

Paint a spot onto the shellac lid. If it also stays soft, the shellac is to blame. That's the standard test for freshness.

[Swingman]

I spray only, usually with a 1# cut, using BORG quality "denatured alcohol" on the good days, 99% anhydrous on the dicey, and have the exact same results.

I'm thinking, judging from his description, that the OP' is applying too thick and too many.

Just a SWAG ...

[Larry Blanchard]

I don't know if he is, but I sure am :-). Not only is it harder, it's much more resistant to the infamous white water rings. In fact I've taken a glass of ice water and sat it on a test board for several hours without any marking at all.

BTW, a friend has stated that shellac continues hardening for a very long time. My experience has been that it hardens to the touch very rapidly and can be sanded (carefully, without generating too much heat) the next day.

I also apply shellac with a "rubber" or a rag. No brush marks and I can apply the first 3 or 4 coats with almost no pause between them. Then about an hour between each of several more coats.

[Lew Hodgett]

Thank you for the info.

BTW, "Rag" I understand, but "rubber"?

Lew

[nospambob]

[C & S]

It's a French polishing term... basically a wad of cloth wrapped with another cloth for a smooth tight surface, used as an applicator pad.

-Steve

[Andy Dingley]

aka "tampon" if you're reading French books -- and George Franks is the best book to read on such things.

Making a rubber is a key skill in french polishing (English style) and even more critical for doing it French style.

Take a pad of cotton waste (not cotton wool), which is collected strands of cotton or worsted that are loosely packed together. Make an egg of this with a pointy end. Now wrap it in a piece of cloth. Linen is the best (tea towels, handkerchiefs) or top-quality long-staple cotton from old dress shirts or boxer shorts. Nothing else works. Splash some meths onto the cotton waste and then twist the cloth tightly around it. Dribble some of your shellac onto the rubber and set to work on some smooth scrap timber. It takes a good while for a rubber to "bed in", which is why you store them in a closed jar at the end and keep them for the next day. Just wake them up with a splash more meths first.

Really you need to see pictures for how to get the proper "strangled mouse" look to it. Read a good finishing book.

French-style polishing uses pumice as an abrasive on the rubber itself (English does it separately, once hardened). This is why a top quality fabric is essential. Anything else (cotton canvas, soft cottons, cotton jersey, denim, linen blends, synthetics, Cordura, Kevlar) just doesn't work. I've tried them!

[Lew Hodgett]

Think I'll let someone else do it, it is way too much for me.

Thanks for the info.

Lew

[Nova]

Yes. Look at the clarity of dewaxed/decanted shellac verses that straight out of the can. Dewaxed/decanted shellac will be clear. Shellac out of the can is very cloudy.

Most complaints common to a shellac finish are wax caused. These complaints include poor wear resistance, water rings, moisture resistance and a soft finish.