Europe Discovers the Wonders of Shellac
Following the historical journey of Marco Polo to the Orient in the late 13th century, shellac and its by-products began to make their way into European commerce and industry. Accounts dating as far back as 1534 describe the cultivation, harvesting, processing and use of lac in extraordinary detail.
By the mid-17th century shellac resin, shellac dye and shellac wax were used with increasing frequency by painters not only to create their masterpieces, but also to provide them with a protective finish.
Shellac became the preferred finish for craftsmen and artisans; it was the coating of choice for fine furniture, woodcarvings, and turnings. To this day some of the finest museum pieces still have their original shellac finish.
The Golden Age of Shellac
Ironically, it wasn’t until the mid-19th century that shellac was commonly used as a clear finish. Until that time it was processed mainly for the dye that was extracted from the lac after it was harvested. This rich, reddish-purple colorant was highly prized and much sought after by the textile trade in both Europe and America because it was an excellent substitute for Cochineal, a dye imported from Spanish colonies in Mexico.
In 1856 an English chemist named Henry Perkin succeeded in synthesizing a mauve-colored dye from an aniline derivative of coal tar. His discovery forever changed the future course of the shellac industry. As the demand for natural lac dye declined, the demand for shellac varnish began to increase. Production plants began springing up throughout Europe, most notably in Germany, which soon developed a reputation for manufacturing the finest shellac in the world. Efforts were also being concentrated on producing colorless shellac. As far back as the 1830’s shellac chemists discovered that by chlorinating an alkaline solution of shellac they could remove almost all of the color and then precipitate the resin. The result was a pale, straw-colored varnish that excelled any oil-base varnish for clarity.
Machine Made Shellac is produced in two different ways-Heat processes and Solvent process. Separation of pure lac is achieved by melting seedlac by steam heat and squeezing the soft molten lac through a filter by means of hydraulic presses.
Almost everyone has heard of Shellac, but very few truly understand it’s origin and common uses. Shellac is perhaps the father of the modern plastics industry; the fact is that the original goal of this industry was to replicate the characteristics of shellac with various additional qualities. These attempts lead to forks and turns in the road to a vast array of industries and products.
The original cultivation of shellac was not for the resin as a furniture finish, but rather, for the dye that gives the resin its characteristic color. Shellac is remained an important export commodity for India and Western Europe throughout its history. The use of lac dye can be traced back to 250 AD when it was mentioned by Claudius Aelianus, a Roman writer in a volume on natural history.
The first use of shellac as a protective coating appears as early as 1590 in a work by an English writer while visiting India and documenting local cultures, an extract from his text provides one of the earliest known observations of shellac application.
Shellac manufactured by modern mechanical methods is called machine-made shellac, mainly to distinguish it from shellac made by the indigenous – and, frankly, more fascinating – hand technique. There are two processes – one based on melting (heat process) and the other on solvent extraction.
In the heat process, seedlac is melted on steam-heated grids. The molten lac is forced by hydraulic pressure through a fine wire screen. The filtered shellac, still molten, is collected and transferred to a steam-heated kettle from which it is dropped onto rollers. It is squeezed out on the rollers, coming off as a thin sheet to be broken into flakes. The thickness of the flake is controlled by adjusting the roller pressure. All flake shellac produced by this process contains wax.
The solvent process produces three types of shellac:
- For the wax-containing grade, raw seedlac and alcohol solvent are charged into a dissolving tank. The solution is refluxed for an hour or so and then filtered to remove insolubles. The filtered shellac is fed to a series of evaporators where it is concentrated into a viscous melt, which is then dropped onto rollers that sheet it out for removal in flake form. Darker, wax-containing flake shellacs such as Garnet are made this way.
- Dewaxed shellacs are made by dissolving seedlac in either cooled alcohol of a very high proof or heated alcohol of a lower proof. The resulting solution is then passed through a filter press to remove the wax, after which the filtered shellac is then concentrated in evaporator tanks. The viscous shellac is then rendered into flakes. Dewaxed Lemon and Dewaxed Garnet shellacs are manufactured using this process.
- Dewaxed/Decolorized shellacs are made by the same process as dewaxed grade, except that after dewaxing the solutions are forced through activated carbon filters to remove the darker coloring constituents from the shellac. By varying the amount of carbon, contact time and quality of the seedlac, one can obtain grades of shellac ranging in color from light amber to extremely pale straw. Examples of these shellacs include Blonde, Super Blonde and Ultra Blonde.