Mixing Shellac
2013.11.09
The long legacy of shellac includes an unusual unit of measure for the ratio of shellac to alcohol, called a “pound cut”. A one pound cut would be a pound of shellac flakes dissolved in a gallon of alcohol, a three pound cut would be three pounds of flakes per gallon. This combination of dry mass and wet volume measures, not to mention the absurdly large quantity for a typical furniture project, can really make you scratch your head. There are tables on the internet to work out smaller proportions, and fortunately it does not have to be particularly precise. Nonetheless, since I’ve never mixed it before, I used a measuring cup and postal scale.
I purchased dewaxed flakes from Shellac Shack in orange and platina, following the principle of “clear, color, clear”: a clear coat, then color coats to tint as desired, then a clear coat on top. After some research, I settled on brushes with synthetic Taklon bristles. They have a distinctive orange color and are available from various suppliers.
Most people use denatured alcohol from the home center, and are happy with the results. However, for two separate reasons I took a different course. (First an aside: the alcohol is denatured — made poisonous or at least unpalatable — so that people will not drink it, thus avoiding liquor taxes and licensing.) One of the potential problems with shellac is a milky, cloudy appearance caused by either too much humidity in the air or too much water in the alcohol. With humidity mostly under control due to running a dehumidifier in my shop (keeping it around 50%), I wanted to further avoid this problem by using a high-grade alcohol with very little water. The other issue is that denatured alcohol is usually almost half methanol, which is rather toxic. Formulations vary, but often also include isopropyl alcohol, acetone, methyl ethyl ketone, etc. To avoid these issues, I purchased a bottle of Everclear (190 proof), which is 95% ethanol.
To fill the little half-pint mason jars with a one-pound cut, I needed a half ounce of flakes to four ounces of alcohol. Based on various sources, I decided thinner coats would be easier to manage, even though it might require more of them.
To speed up the process, some people recommend pulverizing the flakes in a coffee grinder or some other method. I just used the flakes as they were for this first round. Periodically I opened the jars to stir the flakes with a craft stick. If you let it sit too long, the shellac will gum onto the bottom of the jar.
2013.11.10
By the end of the day, the two jars were mixed pretty well, but I let them sit overnight. I then poured each into a clean jar through a paint strainer to catch any undissolved solids.
Shellac