12/18/02 I make a KD storage cabinet that I finish with Shellac. Last summer, in the high humidity, I had trouble with parts sticking together even after installing air conditioner and letting them sit for several weeks. I also used wax paper along with sheets of foam packing in between parts, but the parts still stuck to the parts, and the wax paper also stuck to the parts. Does anyone have any suggestions as to how I can prevent this problem from occurring next summer? Any help would be greatly appreciated.
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Try Knots.
Tom
It sounds like your shellac may have been "out of date". A general rule of thumb is to avoid using shellac that is more than six months old. If you're buying yours rather than mixing it from flakes, check the date on the can. Or better yet, put a drop of it on the lid of the can and wait to see if it will harden properly. If it's soft enough to easily dent with your thumbnail after 8 hours, it's questionable. I'd probably chuck it at that point, but if you want you could wait another day to see if it will dry at all. If it's old enough, it won't ever harden. Although somewhat rare, I've heard of shellac only three months old that failed to harden so the test is the way to go if you have any doubts at all.
Even moderately high heat can soften even good shellac. You may have a combination of the two effects.
I might suggest that you strip the shellac and start over. Denatured alcohol will do the job. Unless you need the shellac for a barrier coat against silcone contamination, I'd recommend that you choose a different finish as shellac doesn't offer much in the way of durability or resistance to water, alcohol and a host of other liquids. Oil-based poly would give you a good durable surface for a storage cabinet.
I suppose you might try applying a different finish over the shellac, but there's no guarantee about the results if the shellac is unhardened and sticky.
The shellac never cured properly. Mind, you, what do you mean by high humidity? Like Houston, TX., type high humidity, or even mor humid? Even in places like Houston, properly cured shellac polishes in normal residential situations won't suffer from this kind of imprinting after even just a few days of curing.
So, this begs the question, what kind of shellac did you use? Was it one of the canned pre-mixed types with a use by date printed on the can? Was it out of date?
Did you mix up your own shellac from flakes? How old were they, and had you kept them in a cool dry place in a sealed container? Stored flakes can go bad if they aren't stored as I described, won't dissolve properly, and if used, won't cure properly.
If you made up your own polish from flakes, what was the solvent, and what type of shellac was it, e.g., super-blonde dewaxed, etc..
You'll need to answer questions like this to establish what might have gone wrong so that a strategy for dealing with the problem can be suggested.
At this point, unless your reply comes up with information that is quite startling, it's my experience that problems like yours can usually only be dealt with by stripping the lot and starting again. And it wouldn't hurt to post your question over at Knots in the Finishing forum too as has been suggested, and don't forget Jeff Jewitt's forum at Homestead Finishing-- the man certainly knows his finishes and has many expert solutions to finishing problems. Slainte.