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amateur
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The most recent issue of Fine Woodworking had an article about using Shellac and one of the cautions that the author mentioned was not using old Shellac. Unfortunately, I am not entirely clear what he meant.

I understand that when you mix Shellac with denatured alcohol it has a very short shelf life (weeks perhaps?). What I am not clear on is the shelf life of Shellac flakes. Do Shellac flakes degrade over time, or are they pretty stable?

Greg
 

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In History is the Future
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Flakes last a very long time, premixed at lowes has a shelf life of 3 years...
Zinnser Shellacs have an additive (they deny it) which is supposed to keep it good for longer.

Shellac flakes have an indefinite shelf life if kept very dry and sealed up. Once mixed with ETOH it it begins to break down and will have a much shorter life. A month at most then is time to throw it out - fresher is better.
 

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amateur
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Discussion Starter #5
Thanks guys.

Recap, flakes last a long time. Premixed quickly goes bad.

Greg
 

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Thanks guys.

Recap, flakes last a long time. Premixed quickly goes bad.

Greg
Well, "quickly" is relative. It will generally last 6 months if well sealed. Personally, I make up whatever I need and use it up. I HAVE kept some around for a few months though and it's fine.
 

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I have a can of premixed amber shellac that is probably 20 years old. I have to thin and strain it but it otherwise works fine. The reason the flakes are popular is it will nearly last forever on the shelf.
 

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Shellac can be tested to see if it's still useable, I usually put a small amount on a piece of glass. If it hardens within 20 minutes or so, you're good to go. Zinnser quite putting a readable code date on their cans, so this is a useful way to gauge whether it's good or not. I mix a lot from flakes, and if i have leftovers they go in a small fridge in the shop...I've kept it as long as 8 months doing that. The Zinnser goes into the fridge as well. Doing this slows the chemical reaction that makes it unusable. I stick my flakes in the freezer compartment only because it's unused for anything else.
 

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Yeah, I put my flakes in an opaque bag in the bottom crisper. I read somewhere that refrigeration alone is enough but I guess freezing would be at least as good if not better.

I never thought about actually refrigerating the mix itself for longer shelf life. Good idea, but if my wife ever mixes any of it with her tea, I'm in for trouble :smile:
 

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Yeah, I put my flakes in an opaque bag in the bottom crisper. I read somewhere that refrigeration alone is enough but I guess freezing would be at least as good if not better.

I never thought about actually refrigerating the mix itself for longer shelf life. Good idea, but if my wife ever mixes any of it with her tea, I'm in for trouble :smile:
Mixing it with tea would be bad, so would confusing it for a apple juice.....:laughing:
 

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I have used shellac extensively for the past 15 years. I usually import between 50 kg - 100 kg of various colors of dewaxed shellac. I can tell you that when we make a batch it gets dated. The shelf life for the mixed shellac is 6 months, then it begins to degrade. Usually a mixed batch was used up in less than a month. But the amount that we left in the shop for samples was thrown away after the six months was reached. Also it is wise to keep the shellac flakes in a cool and dark place. A refrigerator would be nice but it was not big enough to hold the large amounts of shellac we had on hand.
 

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Also never mix your shellac in an unlined metal can as it will turn dark and degrade very quickly. Use a glass jar for small amounts, or as we do use 5 gallon pails for large quantities.
 
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