Official Luthiers Forum!

Ever open a can of finish or glue only to see a semi hardened skin on top of the contents? That's because oxygen was trapped inside the can the last time you closed it. These products cure by interaction and exposure with oxygen which is called oxidation. Here is a tip, that my dad taught me 60+ years ago, which will prevent premature drying. Put the lid on the can or bottle but just slightly opened on one side. Take a deep breath and blow into the can and as you are running out of breath, close the lid tightly. Your exhaled breath contains carbon dioxide, which displaces the oxygen in the can and replaces it with C02. The contents will now remain fresh with no skin on top the next time you open a can.

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tim...
http://www.mcknightguitars.com

Tim,
With all due respect to your Dad, might there be other explanations for less skinning over?
Ambient air runs about 21% oxygen, while exhaled air runs about 16.4% O2. We only use about 5% of the oxygen we breath in and out. That leaves plenty of oxygen in the can.
Bags for storage, that you can squeeze the air out of, or products like Bloxygen that displace the air in the can with more unreactive gases are probably more effective.

Didn't think of that.
I just bought a can of argon gas for the same reason.
https://www.winesave.com/

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I never had much luck with the 'inert gas' method. It only takes 1/3 of a can of air with 20% oxygen to harden the rest of the can, so you really need to limit the amount of air.

The best thing I've found so far is to simply keep the varnish level at the top by putting marbles in as I go. You can use about 2/3 of a can of varnish before the marbles fill it up. What I do is start with a gallon of varnish, and divide that up into four quart cans. When those get full of marbles I consolidate the vanish into one quart plus a pint can. The marbles are saved, rinsed off with a little thinner, and re-used. Use the pint up first.

One key to this is keeping the rims of the cans and the tops clean by wiping them down before you put the top back on. I had to destroy the first can I did this with when the varnish hardened up to the point where the top would not come loose. Don't even think about a jar with a screw top... One of my students found a place on line that sells new empty paint cans and got me a bunch several years ago, so I'm all set for when I can no longer use a can.

I've been doing this for twenty years and have not had to throw out any varnish in that time. Of course, once I lose my marbles I'll have to give up lutherie...

Nice one Sir.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I don't have a scientific explanation for what I stated above other than just what dad taught me to do and dang if it doesn't work quite well. It even works on food products to keep them fresher longer. I would suggest giving it a try. What have you got to lose?

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tim...
http://www.mcknightguitars.com

I wonder if there's something else in exhaled breath that impedes the varnish's ability to absorb oxygen. Is there a chemist in the house?

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formerly known around here as burbank
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http://www.patfosterguitars.com

You could be right Pat. I am certainly no chemist nor do I play one on TV. I always just assumed it was C02. Perhaps its just plain old "bad Breath?

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tim...
http://www.mcknightguitars.com