Shellac is a very useful tool in the decorative painter’s toolkit. It is one of the most versatile and yet under utilized medium. We have a small jar on every job because of it’s many uses (see below). Shellac is one of the oldest paint mediums, used in Ancient Egyptian and Roman times as a fixative and varnish. It has excellent durability and dries fast and hard.
Shellac’s origins begin with a female lac bug, who secretes a resin meant as a protective cocoon for their larvae. The resin is scraped off trees, placed in a straining mechanism and heated. The resin liquifies and drains (leaving impurities behind) onto a flat sheet. When dry, it is broken into flakes and sold in that form.
These resin flakes are used in many industries including culinary (yes it’s edible), cosmetic, textile, and the painting industry. The flakes are dissolved in alcohol (ethanol) to make liquid shellac.
There are three different types of shellac: amber (natural), clear (refined), and white (opaque).
The amber is faster drying, more potent and is most commonly used in our shop. Clear shellac is great as a varnish and surgical touch-ups. White is used as an opaque primer. The alcohol in the shellac evaporates very fast, forcing the mixture to thicken rapidly, and therefore making the shellac very difficult to brush. When applying a second coat, the first coat is reactivated – an additional challenge. These hurdles can be discouraging, but it’s worth mastering application techniques (confidence and speed are key). We always thin shellac from a can with 20% denatured alcohol – to give more open time.
Important qualities and uses for shellac (for the decorative painter):
* Reversible – once dry can be reactivated with alcohol to revert back to liquid
* Performance primer – it levels well (few brush marks), sands easily and provides a shiny surface, perfect for receiving paint
* Seals very porous surfaces – wood, raw plaster (see post: plaster repair)
* Isolation coat to prevent bleeding of resin (wood knots), pigments or odors from escaping
* Isolation coat to start fresh from impure or questionable surfaces – such as an unknown treatment or wax residue (if a waxed surface needs to be painted over/changed, clean the surface with Naptha to remove the wax, since there’s always a residue remaining, seal the surface with a coat of shellac to insure a strong bond to the paint)
* Used in French Polish technique
* Gilding: super smooth and isolate surface before using oil size in preparation for gilding
* Wood inlay and other paint techniques using Gouache (reversible medium with water) – seal the finished wood inlay “pieces” that are finished and wipe off areas with water that remain unfinished (this eliminates the need for tape)
* Furniture touch-up – mix shellac with powdered pigment
* Overall problem-solver – great with a wide variety of touch-ups (see post: plaster touch-up, and patch a hole)