Storing shellac

I have a 3/4 full can of shellac that's been on the shelf for over a year. Lid is tight, no problem with the contents, but the top sides of the can started to collapse. I used a little the other day and put everything back and the bottom of the can developed a hole and leaked onto the shelf until it built up enough around itself to clog the hole. I drained the material from the can and put it in a plastic container with a lid. Can I store it in this or must it be glass or metal? Is this normal for the can to deform over time based on this contents? Thanks Brian

I had a can of it fall apart. Never figured out why. I would only use a glass container now.

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Originally Posted by Brian Runau

I have a 3/4 full can of shellac that's been on the shelf for over a year. Lid is tight, no problem with the contents, but the top sides of the can started to collapse. I used a little the other day and put everything back and the bottom of the can developed a hole and leaked onto the shelf until it built up enough around itself to clog the hole. I drained the material from the can and put it in a plastic container with a lid. Can I store it in this or must it be glass or metal? Is this normal for the can to deform over time based on this contents? Thanks Brian

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Premixed shellac has preservatives in it for longer shelf life, but even that is limited. Test it by applying some to a surface & let it dry. If it's still soft & a little tacky the next day then it's about done. For storage, some plastics will pass solvent vapors, so metal or glass would be best.

Only partially related, but I tried using a shot of freeze spray on a part can of Tung oil to displace the oxygen. I noticed about a week later that the can had collapsed to the point where the oil was right at the top. I guess that the freeze spray gas must have dissolved into the oil, collapsing the can. The Tung oil was still good.

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Originally Posted by Brian Runau

I have a 3/4 full can of shellac that's been on the shelf for over a year. Lid is tight, no problem with the contents, but the top sides of the can started to collapse. I used a little the other day and put everything back and the bottom of the can developed a hole and leaked onto the shelf until it built up enough around itself to clog the hole. I drained the material from the can and put it in a plastic container with a lid. Can I store it in this or must it be glass or metal? Is this normal for the can to deform over time based on this contents? Thanks Brian

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I don't know if shellac degrades with moisture, but I do know that plastic will let moisture through. I think oxygen degrades many finishes.

What I do for all finishes, cans, bottles, etc, is add a little nitrogen or argon from a tank I keep in the shop, then close the lid right away. Since I've been doing this finishes in cans seem to last forever.

The Bloxygen product (argon in a can) works well. http://www.bloxygen.com/
Somewhere on their web site they tell the approximate number of quarts or gallons that can be protected.

JKJ

The alcohol in the shellac slowly degrades the shellac molecules over time to the point where it eventually won't dry. Zissner used to say their stuff was good for 3 years, although I try not to buy more than I can use in about 18 months. Blonde degrades faster apparently due to the beaching process. You could use shellac flakes and mix with alcohol to use when you need it, but I've found that to be too much of a hassle to want to do it regularly.

Shellac is also acidic, so any nick in the coating on the inside of the can will allow it to start eating through the metal. Eventually it will get through and leak everywhere. I've had a two or three cans do that over 30 odd years.

I would probably dump what you have and just get new stuff. It might work and it might not. Considering shellac isn't that expensive and it is getting towards the end of its life anyways, I wouldn't want to risk ruining a project with it.

Bullseye shellac will last 2 years or so in an unopened can, less after it's opened and exposed to moist air unless you back fill the head space with Bloxygen, et al. The leakage you observed is well known among users like us unlucky enough to have had it happen, but also to Bullseye, yet they won't or can't figure out how to fix the problem. The solution is to transfer it to a Mason type jar and back fill with Bloxygen. That prevents corrosion of the can and limits aging of the shellac.

As long as shellac dries and cures hard it's good.

John

Thanks men. Brian

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Shellac is also acidic, so any nick in the coating on the inside of the can will allow it to start eating through the metal. Eventually it will get through and leak everywhere. I've had a two or three cans do that over 30 odd years.

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Yes - very much so.
Another very annoying thing that can happen is when the shellac attacks the a metal can is that,
it builds pressure up that will eventually cause the lid to blow off & take quite a bit of gooey, sticky, non-drying shellac-goo with it.