I mix my own shellac for French polish. I’ve been told it deteriorates in storage, but not how. Care to fill me in?
Kevin Hancock: Esterification is a process of gum formation that begins when shellac is mixed with alcohol. The more esterification, the softer the film and the longer the drying time. Eventually, the shellac will fail to dry at all. It is best to mix only what you plan to use in the next few months. Interestingly, the newer mixes of shellac from Zinsser, such as SealCoat and French Polish, have a shelf life of three or more years thanks to a patented process that delays esterification.