| Most traditional makers concoct their own formulas, but it's generally some type of alcohol-based varnish with various combinations of resins like pure shellac, sandarac, copal, benzoe etc., and colors such as hibiscus extract or dragon's blood. Generally the white (unfinished) instrument is hung in a sunny window for a few months until the wood gets a nice golden glow, and then the varnish is applied water-thin with a brush, often 50-100 coats, and french-polished. It's a very soft, thin finish, easily damaged.
Probably most mass-produced student type instruments are sprayed with lacquer or something, but I'm not sure about that.
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