Shellac is a resin that is scraped off the bark of trees where the female lac bug secretes it to form a tunnel like tube. The raw shellac, which will contain bark shavings and lac bugs, is placed in canvas tubes and heated over a fire. The shellac will start to liquify from the heat and seep out of the canvas tube. The thick, sticky shellac is left on large sheets to dry where it is broken into flakes and bagged.
To process the flakes, the resin is dissolved in ethanol to make liquid shellac. Liquid shellac has a limited shelf life(about a year), so always check the manufactures date or buy the flakes and mix yourself. Because shellac naturally contains small amounts of wax, dewaxed shellac can be purchased. Dewaxed shellac is used for applications where it will be top coated with another product.
Shellac acts as a natural primer, sanding sealant, tannin-blocker, odour blocker, stain, and a high gloss varnish. It appears milky in liquid form, but will dry clear. Shellac comes in many colors from very light blond to very dark brown, with many varieties of brown, yellow, orange, and red in between.
The finish of shellac scratches more easily than most lacquers and varnishes. As well its application process is more labour intensive. The upside to shellac is when its surface is damaged it can be easily touched up with another coat of shellac. Shellac is UV resistant, does not darken with age, and dries very quickly.
Advantages of Shellac:
- Non yellowing compared to varnish
- Quick drying
- Wide variety of colors
- Super adhesion
- Excellent sealer
- Excellent hardness
- Ease of repair
- Ease of removal
- Can be padded, brushed, and sprayed on
- Food safe
- No unpleasant or toxic fumes
Disadvantages of shellac
- Re-dissolves in alcohol
- Forms white rings on contact with water
- Shows scratches easily
- Liquid form has a shelf life
- Not resistant to alkaline compounds
- Sensitive to heat