Use Pre-Mixed Zinsser Shellac Products

Shellac that has gone beyond its shelf life will not come to a cure on your project, leaving you with a tacky mess. So how can you tell if your Zinsser product is good to use?

If you are purchasing Zinsser shellac from your local paint or hardware store, Zinsser literature states that their product has a three year shelf life.

Before you purchase your next can of Zinsser shellac, take a look at the top lid of the can and check the code.

You will see the word LOT. Followed by a letter which identifies where that shellac was packaged.
The first number after the first letter is the last digit of the year it was packaged. This is the first thing I look for on all the cans on the shelf! So if the number is 7, that means it was packaged in 2017. Vendors sometimes do not rotate their stock.
The second number is the month it was packaged.
The third and fourth numbers relate to the date within the month it was packaged.
The fifth number or letter refers to which batch of the day the shellac was packaged. Meaning, there may have been five different batches of shellac packaged that particular day. So that can would have a 5 at the end.

Tips for Mixing Your Own

For those of us who prefer to mix our own shellac from flakes or buttons, shelf has the same concerns. A rule of thumb is to mix as much shellac that you are going to use in the next six months. I have made shellac that has lasted much longer than six months, but I always test it on some scrap wood (that I have sanded) to make sure it is functional.

I prefer not to use store bought denatured alcohol for my shellac. Reason being that most denatured alcohols contain methanol, which is used to "denature" ethanol. Ethanol can be denatured with other solvents that are much less toxic. Behlan sells a product called Behkol Solvent and Mohawk Finishing Products sells Shellac Reducer which are both methanol free. If you're near a liquor store that sells 180 proof Everclear, it makes a very excellent and safe way to dissolve your flaked shellac (though I am not responsible for what you do with any leftover Everclear once the shellac is made).

Finally, I use a coffee bean grinder to first pulverize my shellac flakes. It really expedites the process of dissolving the shellac.

I hope these tips will help you explore shellac finishes with greater success!
Mitch
mitch@woodfinishing.org