How long does Shellac last (I mixed flakes and isopropyl alcohol)

[Luis Reyes]

I mixed some garnet Shellac wax last May with isopropyl alcohol. Would it still be ok to use? Should I try it on some scrap wood?

Thanks

Luis

[roger wiegand]

Put some on a scrap board. If it is good it will dry within 30 minutes such that it powders when sanded, at least when dissolved in denatured alcohol, ethanol. or a proprietary solvent like Mohawk shellac reducer.

Never tried isopropanol, it might be slower to evaporate. Isopropyl is an azeotrope (picks up water from the atmosphere) and will contain 10% water after it has been sitting around for a while, about double what ethanol picks up. I can't believe that's good for the shellac or for its drying speed. For the gallon or two a year that I use I stick with the shellac reducer for consistency (cans labeled "denatured alcohol" can be very inconsistent in what they contain), and find that the shellac stays good for as long as two years. I've never actually had shellac prepped from flakes last long enough in the shop to go bad on me, not so for the pre-made canned stuff.

[Jim McCue]

I've used shellac that old before.

The technique I read was to test on glass, but I guess you could test on a plate or even wood scrap. If it's not good anymore it will stay gummy.