About Shellac
Shellac was used from the 1800s century to produce small moulded goods like picture frames, boxes, toilet articles, jewelry, inkwells and even dentures. Although advancement in plastics have rendered shellac obsolete as a moulding compound, it remains popular for a number of other uses. In dental technology, it is still occasionally used in the production of custom impression trays and (partial) denture production.
Shellac is used by many cyclists as a protective and decorative coating for their handlebar tape. Shellac is used as a hard-drying adhesive for tubular cycle tires, particularly for track racing.
Orange shellac is also the preferred adhesive for reattaching ink sacs when restoring vintage fountain pens. It has always been the preferred hot-melt adhesive for fixing leather saxophone pads into their metal key-cups.
Until the advent of vinyl around the 1940s, most gramophone records were pressed from shellac compounds. This use was common until the 1950s, and continued into the 1970s in some non-Western countries.
Sheets of Braille were coated with shellac to help protect them from wear due to being read by hand.
Shellac is used as a binder in India ink.
Shellac was historically used as a protective coating on paintings.
Shellac is edible and it is used as a glazing agent on pills (see excipients) and candies in the form of pharmaceutical glaze (alternatively, confectioner’s glaze). Because of its alkaline properties, shellac-coated pills may be used for a timed enteric or colonic release. It is also used to replace the natural wax of the apple, which is removed during the cleaning process. When used for this purpose, it has the food additive E number E904. This coating is not vegan and most likely not vegetarian either as it may, and probably does, contain crushed insects.
Because it is compatible with most other finishes, shellac is also used as a barrier or primer coat on wood to prevent the bleeding of resin or pigments into the final finish, or to prevent wood stain from blotching.
Shellac is an odour and stain blocker and so is often used as the base of “solves all problems” primers. Although its durability against abrasives and many common solvents is not very good, shellac provides an excellent barrier against water vapour penetration. Shellac based primers are an effective sealant to control odours associated with fire damage.
Shellac was once used for fixing inductor, motor, generator and transformer windings, where it was applied directly to single layer windings as an alcoholic solution in much the same manner as it is applied to timber. For multilayer windings, the whole coil was submerged in the shellac solution and then removed, drained and placed in a warm place to allow the alcohol to evaporate. The shellac then holds the turns in place, provides extra insulation and prevents movement and vibration, reducing buzz and hum. In motors and generators it also provides a medium for transfer of forces generated by magnetic attraction and repulsion from the windings to the rotor or armature. In more recent times synthetic resins, such as Glyptol, (Glyptal), have been substituted for the shellac. Some applications use shellac mixed with other natural or synthetic resins, such as pine resin or Phenol-Formaldehyde Resin, of which Bakelite is the best known, for electrical use. Mixed with other resins, Barium sulfate, Calcium Carbonate, Zinc Sulfide, Aluminum Oxide and/or Cuprous Carbonate, (Malachite), shellac forms a component of Heat Cured Capping Cement used to fasten the caps or bases to the bulbs of electric lamps.
As a natural resin, shellac has similarities to other natural resins such as Myrrh and Frankincense.
Shellac finds a use in pyrotechnic compositions as a low temperature fuel where it allows the creation of pure ‘greens’ and ‘blues’, colours difficult to achieve with other fuel systems in fireworks formulae.
Further info:
- It takes about 100,000 lac bugs to make 500 g of shellac flakes.[5]
- Shellac is UV-resistant, and does not darken as it ages (though the wood under it may do so on its own, as in the case of pine).[5]
- Shellac scratches less easily than most usual lacquers, and damaged areas can easily be touched-up with another coat of shellac (unlike with polyurethane) because the new coat merges with and bonds to the existing coat(s), but shellac is much softer than Urushi lacquer for instance, which is far superior in regards to both chemical and mechanical resistance.