Shellac question

[Vic Baron]

I'm puzzled. I've always read that shellac has about a 6 month shelf life and to toss the old stuff after that time. About 18 months ago I made up some 2# cut of shellac from scratch. After I was done with it, I kept it in a sealed plastic bottle.

Out of curiosity I took it out this weekend and used it straight from the bottle on a small test project just to see what happens.

Nothing. It *appears* just fine. Dried quickly and firm. I was able to scuff sand between coats. Tried brushing and padding - same thing - no problem.

Is there a hidden downside or did I just get lucky?

Not the most earth shattering issue of the day but a curiosity to me none the less.

Thanx,

Vic

[Woodie]

Artificially short shelf life predictions are published to ensure that new product gets produced and sold. Just another reason to hate and fear scientists.

[joeljcarver]

the old stuff after that time. About 18 months ago I made up some 2# cut of shellac from scratch. After I was done with it, I kept it in a sealed plastic bottle.

bottle on a small test project just to see what happens.

Keeping shellac a sealed bottle just keeps the alcohol from evaporating. Shellac contains organics acids that will, over time, react with alcohol to form esters. At that point the shellac won't dry properly. Clearly, the rate of the reaction in your case was slow, but about six months is the time it normally takes for esterification to occur.

Joel

[Steve]

That has NOTHING to do with scientists. It's the marketing folks who dream up that stuff.

--Steve in Roseville

[Woodie]

Scientists are behind it. They always are. Evil, plotting, scary, maniacal scientists.

[jd]

I have had goo dluck using shellac that is as old as 4 or 5 years.

I've never had shellac "go bad".

While I understand the chemistry involved with thetheoretical deterioration of shellac, I've just never experienced it. I use steam distilled alcholohol to make my shellac, almost always use dewaxed stuff, and store it in sealed dark bottles at room temperature (my shop is usually fairly cool, and rarely gets over about 70 degrees F)....

YMMV

-James (who also happens to be a scientist....)

[Steve]

I guess it time for me to let out one of my maniacal cackles! You'll have to imagine it, because I don't know how to spell it.

--Steve, whose job title was >>> Artificially short shelf life predictions are published to ensure that

[Limey Lurker]

I've got a couple bottles of shellac that are at least 25 years old. I don't often use it, but whenever I do I have no trouble with its finish or drying. These are quart bottles; perhaps the larger volume/exposed surface ratio helps preserve it?

[Bill Leonhardt]

toss the old stuff after that time. About 18 months ago I made up some 2# = cut of shellac from scratch. After I was done with it, I kept it in a seale= d plastic bottle.

he bottle on a small test project just to see what happens.

WRT the 6 month life, does the clock start at manufacture or at the first time the factory can is opened?

Thanks,

Bill L.

[Larry Blanchard]

At date of manufacture. But Zinsser puts some sort of preservative in their shellac that they claim keeps it usable for 3 years. I get nervous after two and toss it.

BTW, use the Sealcoat, not the stuff with wax in it. Sealcoat is marketed as sealer, but it's just a two pound cut of dewaxed shellac.

I've been told that the preservative keeps the shellac from ever drying quite as hard as the non-preserved stuff, but I can't tell any difference. If that possibility bothers you, mix your own from dewaxed flakes.