I’m reasonably new to Shellac having only used it on less than 10 projects so far. I tend to favor the dewaxed Hock flakes (various shades) that I melt up myself. I’ve been very pleased with the look and durability of the results.
My question comes from some OLD shellac I’ve seen on various stuff from chairs to Taylor carving chisels where the shellac was sort of brittle – sometimes had stress lines – flakes – and was just generally sort of dry powdery and brittle. I don’t know how else to describe it, but hopefully some of you have seen it and can understand. My question is: Is this just the fate of all shellac over long enough times or is this a phenomemnon that only occurs with certain types of shellac or in certain circumstances where the shallac has been mistreated (left in an unheated garage for a decade sort of thing)??
In short, what can you shellac experts tell me about its durability over the long haul? I know it can be renewed, btw. Thanks.
Replies
Samson,
' No! Some shellac can last for centuries in the right conditions. It's one of our most proven finishes.
On the other hand I had a piano which was starting to show such finish failure after about 70 years or so.. I simply wiped off the old shellac and reapplied new, No sanding, no stripping, no hassle..
Shellac is known to last indefinately. I suspect that it was damaged by amonia based cleaners or has a varnish based top coat. There are some "magic potion" furniture renew products that are basicly a very thin varnish.
Pardon my spelling,
Mike
Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.
What you are seeing can be caused by cleaners containing ammonia as others have already said, but it can also be caused by applying shellac to heavily. Shellac should be applied as thin as possible to achieve the look you want.
It is such a hard finish that if it applied to heavily it will not move with the wood and it will alligator. This should not be viewed as a flaw of shellac but rather a mistake in the application.
RobA.
I'm glad to see that others besides me agree that too thick a coat of shellac is a mistake..
Thin is In!
Along the lines of "Thin is in" here is how a friend of mine teaches shellacing:QUOTEI can give you this simple pointer as a place to start. Forget everything that you know about applying other finishes. In particular, that means forget about the concept of "coats"! Every time you apply another coat of shellac to an existing shellac film you significantly increase the probability of failure, both near and long term. This is especially true if you are attempting to pad on a shellac-only finish. Padding (in my view, the best way to achieve a high quality shellac finish) is actually a continuous process in which a single coat is applied in steps until the finish is refined to a very hard film and a high luster. I would also add (along the lines of changing your focus from "coats") that you need to change your view of what constitutes a good finish film. When we apply varnish, lacquer, or even water-borne finishes we think in terms of "building" the finish film. The best shellac finish is the thinnest film that you can apply consistent with good coverage and an even-depth film. One of my visualizations when I teach a class on shellac is to hold up a single flake of shellac (about the size of a quarter) and suggest that our objective is to dissolve this flake and then spread it evenly over the surface of our test board. Clearly, that is not possible; however, the image helps to reinforce the idea of a thin film. It helps students to think shellac and to loose the varnish or lacquer coat-building mind set. As further evidence of this "think thin" approach I will simply hold up the shellac finish on 200-year-old antiques. Those on which the shellac finish has remained largely intact (and there are many) are those on which the shellac film is quite thin. The ones that have alligatored are those on which the finisher built up a thick shellac film. In using shellac, you increase the amount of resin by mixing a heavier cut, not applying more coats.Finally, application of shellac is best accomplished by padding, not brushing. Attempting to apply more that the first application by brush leads frequently to uneven buildup and stickiness. Brush on the first application, sand flat and then pad on two to three more applications. Sanding should not be necessary unless you messed up during your padding.CLOSE QUOTEHowie.........
Howie,
Good points. I'm a little confused about padding.. do you mean as in French polishing or is it a easier application?
Thanks to all who responded. I've learned some valuable stuff:
1. Apply shellac as thinly as possible - too thick invites alligatoring etc.
2. Don't use cleaners with amonia; I wouldn't have, but it's good to know specifically.
As to the varnish issue, I'm still a bit confused. I thought shellac was the magic coating in that it could go under and over everything? Are there certain types of varnish that should not be applied over shellac?
"I thought shellac was the magic coating in that it could go under and over everything?"
Shellac, as it comes from the insect, contains wax. Usually, this isn't a problem. But the presence of the wax can cause adhesion failures with some topcoats; polyurethane varnish is the one most often mentioned in this regard. For this reason, you always want to be sure to use dewaxed shellac whenever you plan to put a non-shellac finish coat on top of it. Zinsser's Seal Coat (specifically designed to be an undercoat for other finishes) is dewaxed; Zinsser's "regular" shellac is not. And so on.
-Steve
Yeah, I understand about the wax issue, but it's always good to reiterate for others new to shellac. What I was referring to was mudman's statements:
I suspect that it was damaged by amonia based cleaners or has a varnish based top coat. There are some "magic potion" furniture renew products that are basicly a very thin varnish.
What sort of varnish is damaging to shellac?
Oh, I don't think he was saying that the varnish damaged the shellac. I think he was saying was that what appears to be damaged shellac is actually damaged varnish.
-Steve
Ohhhhh ... makes more sense now. Sorry to be dense.
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