X10James
Handyman
Reged: 12/21/03
Posts: 811
Loc: Savannah, GA
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Needed to just seal some little wood pieces and had used up the 2lbs cut I made a while back so I returned to the can of zinzer in the cabinet. It is past it's use by date and I planned to test to make sure it would dry without being tacky and such before using it. The pieces will get painted before use so I didn't think that it was that important if it was a little old as long as it dried properly. I didn't notice anything odd about the can, but when I went to pry the lid off it nearly took my head off! The can was not hot but was under significant pressure! Not too much longer I think it would have blown the lid off in the cabinet all by itself.
I know that in canned goods that botulism can grow in them making them under pressure. Can the same thing grow in shellac?! There were some deposits up above the level in the can that looked like they might have been mold growing, but I would have thought the alcohol in there would have kept anything like that from happening? Did I just get a lung full of botulism? Has anybody else ever seen this happen?
If you're opening an old can of shellac I'd recommend wearing goggles!
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bozodog
Carpal Tunnel
Reged: 12/19/07
Posts: 9938
Loc: SW Michigan
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Did you shake the can up before opening? That's a no, no with several products. (aluminum paint is another one)
I found something on the "use by" dates...
Page 44, bottom left
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Governments don’t bear the cost of anything; their citizens do.
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Bob_Fleming
Carpal Tunnel
Reged: 06/28/01
Posts: 23897
Loc: Eagle, CO USA
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Some people love shellac but, I'm not one of them. It is thinned with alcohol, and it has a definite "use by" date. Beyond that, it will never harden. Since the solvent is alcohol, there is little reason to expect anything to grow in it, so I'm at a loss to explain the pressure buildup.
I would not use what you have, and I particularly would not use it under a paint of any kind. My main reason for disliking the product is that it is not waterproof; even after proper curing it will watermark.
As a kid I remember a painter refinishing our church pews with shellac. Back then, there weren't such things as poly varnish, etc. But any rate, when we sat in the pews the next Sunday, we stuck to them. Didn't harm clothing, as I recall, but it was embarrassing. It finally cured, but this being in a humid climate (St Louis, MO) they were not durable.
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bozodog
Carpal Tunnel
Reged: 12/19/07
Posts: 9938
Loc: SW Michigan
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Shellac is interesting stuff. While it's losing popularity with all the newer products on the market, nothing can beat a hand rubbed finish on a fine piece of furniture. It is also easily repaired by someone familiar with it.
It's still used as a "separation" layer in finishing furniture, keeping a stain from "muddying" up a topcoat, or between coats of stain and toners. It is also used as a "sanding sealer" for an even application of stain on porous woods, and makes for easy sanding of raised grain.
"Thank you, Lac beetle!"
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Governments don’t bear the cost of anything; their citizens do.
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MCA
Carpal Tunnel
Reged: 03/09/06
Posts: 2554
Loc: Illinois
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I often store extra paint in glass jars, instead of keeping a gallon that is less than 1/4 full. It seals tightly and takes up less space. I have many jars of paint including some shellac. Is there any risk of the glass jar exploding due to excessive pressure?
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morrisdancer
"Lunatic"
Reged: 10/27/05
Posts: 7617
Loc: Michigan
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I have read that keeping small amounts of paint in glass jars is a good thing to do! As far as shellac goes, I loves me shellac (it is a pretty finish!), but my concern would be that "expiration date" and I would make sure to write that date on the jar lid.
Liz
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Thanks, Chris and Ernie!
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bozodog
Carpal Tunnel
Reged: 12/19/07
Posts: 9938
Loc: SW Michigan
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I don't think so, MC. I've found the pressure builds up if/when you shake the container on certain products. The ones with the most volatile solvents. Silver/aluminum paint carries the same properties as bombs made from fertilizer and fuel oil. Most of them have aluminum shavings for a bigger b00m.
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Governments don’t bear the cost of anything; their citizens do.
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X10James
Handyman
Reged: 12/21/03
Posts: 811
Loc: Savannah, GA
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no shaking! And it wasn't that old really. A couple of months past the use by date.
I guess it will remain a mystery, but I'll certainly be treating those old cans with more respect from now on. I left the lid off for a week and let it harden up and then threw it away.
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