I presume you're mixing your own shellac recipes fresh. It's a little different with products right out of a can now, because proprietary solvents are now being used in certain shellac formulations to greatly extended shelf life. And due to both shellac expense and tightening screws of air quality regulation in key markets (CA and NY), there are also new hybrid products using other film-forming ingredients than pure shellac. And the MSDS won't tell you what's in it. You might think a major competitor would try to unravel this, but the key chemist/CEO actually controls both mfg doing this kind of thing, and deliberately keeps one side blind to what the other is doing. It's fun just walking into the R&D vaults of some of these big companies - hundreds and hundreds of jars of experimental resins with numbers on them, maybe 2% of which will actually be commercially used. But no, they're not about to tell anyone specifically what's in those little jars.