What is shellac?
Shellac is an organic resin secreted by a small insect, the Tachardia lacca, of the Cocciniglie family. This insect lives on a variety of indigenous plants from the Indian subcontinent and neighboring regions. To protect itself, the insect produces a resinous substance with which a kind of shield is created, of a dark purplish red color. This substance is deposited by insects on the branches of plants and is collected by man for later processing: at this time it is called sticklac and contains, in addition to the resin, also vegetable rests and impurity. The sticklacs are then washed, sieved, refined, dried, and resin sheets are obtained, which are then crumbled and marketed in the form of shellac flakes.
The flakes are dissolved in ethyl alcohol in a certain proportion. This is the ready-to-use shellac that can be applied directly to the wood.
There are various types, more or less pure, more or less ambered.
The history
Its collection was not initially made for the resin, but for the red dye that could be obtained from it. The use of the tincture is evidenced by Claudius Aelianus (about 170-235 AD) in his On the Nature of Animals, but it is supposed to have been known 5 centuries before him.
The dye remained on the market until the mid-1800s, when the introduction of aniline, the first artificial colorant in history, made it disappear from the market.
The first news of the use of shellac as a varnish for wood appears in 1590 in a work by an English writer, but its use did not become important until the beginning of the 1800s, when it became the standard for painting furniture . It remains the most common varnish until the 1920s, when it was replaced by lacquer with nitrocellulose.
Being a non-toxic natural resin, it is also used in pharmacies to coat pills and in the kitchen to make sweets and candies shiny.
Having characteristics similar to current synthetic resins, in the past it has also been used for the molding of objects such as the famous 78 rpm discs, which were composed of a mixture of shellac, inert substances and carbon black.
The “french polish”
Shellac can be applied practically with any method: by brush, buffer or spray. Usually in the painting of guitars the buffer method is used because it allows a uniform application of shellac and a mirror polish, this method is called the “french polish”.
The paint is spread with a buffer, a cotton wool pad covered with fabric. The passes are many, each hand is an imperceptible layer. This process takes a few days. When the paint is sufficient, the surface is leveled by sanding with very fine sandpaper. Then begins the polishing process, which lasts about 3 days and consists of continuously rubbing a buffer with a few drops of shellac on the surface.
Advantages
- It’s natural, it’s not toxic
- Highlights the wood grain
- It is applied in a very thin layer which is incorporated with the wood and does not stiffen it
- It is easily repairable; shellac dissolves in alcohol, small scratches and others imperfections can be repaired with small adjustments; the new shellac melts partially the old one, mixing completely.
- It is easy to remove; in the event of wanting to completely repaint a guitar, the old shellac can be removed with alcohol without the use of aggressive paint removers.