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Shellac

by Jordan Ficklin

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Unless you are a watchmaker, when you think of shellac you probably picture a finely finished piece of furniture, or maybe a fine guitar or violin. As a watchmaker I use it too, but in a different form.

Shellac is a resin secreted by insects of the lac family. Two common members of that family are Tachardia lacca and Kerria lacca. The resin is a secretion from the female deposited on the bark of trees. Most of the shellac harvested in the world comes from Thailand and Southeast Asia. Once harvested the shellac is purified into clean flakes known as seedlac.

One of the great properties of shellac is that it can be dissolved in some alkaline solutions as well as some organic compounds like alcohol. When dissolved in alcohol shellac can be applied to woods and forms a hard surface (lacquer). Shellac is a natural polymer considered a plastic. It softens when heated but returns to a very hard substance when cooled. Over time and after repeated heating and cooling the shellac breaks down and ceases to from strong bonds.

In watchmaking we take advantage of shellac’s bonding capabilities as well as its ability to be softened and re-hardened. Shellac is commonly used to hold pallet stones in place as well as roller jewels. In this application the stones are adjusted in their slots to provide the proper depth when interacting with the escape wheel teeth and then a small amount of shellac is melted to hold them in their position. If the pallet fork needs to be further adjusted the pallet fork can be heated and the stones can be moved, the shellac will then re-harden holding the stones securely in place. Since shellac dissolves in alcohol care should be taken when cleaning a watch not to use alcohol on the pallet fork or balance assembly.

3 Comments

  1. Tony
    Posted November 24, 2008 at 6:48 pm | Permalink

    It funny that you blogged about this because we had our shellac lecture on Friday! Today, I used shellac for the first time by turning a square into a circle. It’s neat stuff and definitely takes some practice to get good at it.

  2. Posted November 25, 2008 at 9:27 pm | Permalink

    Great background J.Peter. I met a watchmaker once, who grew up in and learned the trade in China, who said that he uses straight furniture shellac (seedlac). Judging by the darker coloration and brittle quality of the shellac on the pallet fork he showed me, I’m led to believe that what we use is a much more purified form of the resin. I knew another watchmaker who would “purify” the shellac himself by dissolving it in alcohol and allowing the liquid to evaporate off, leaving a gradation of shellac behind on the walls of the container it had been left in. Seemed like an awful lot of effort to try and process what was left behind, and I have no idea how successful the technique is. I use a small vial of watchmaking shellac that only cost me a few dollars.

  3. Vince
    Posted November 28, 2008 at 8:53 am | Permalink

    Shellac is sold in several grades. The more refined it is, the lighter the color. The shellac in the photo you posted looks like orange shellac, which is fairly refined. Blonde shellac is lighter and super-blonde is almost clear.

2 Trackbacks/Pingbacks

  1. [...] bark of trees. Most of the shellac harvested in the world comes from Thailand and Southeast Asia. Read More|||The varnish may contain secretions of Kerria lacca which is an insect of a most revolting [...]

  2. [...] KERRIA LACCA http://pohazo.sytes.net/ KERRIA LACCA KERRIA LACCA. Read More|||Shellac is a resinous compound secreted by the female lac bug (also known as: kerria lacca, laccifer lacca, carteria lacca and tachardia lacca) to form its cocoon. Shellac is used as a coating on medicines and candies. Read More|||Shellac—which is used to make that shiny coating on jelly beans and to give fresh fruits and vegetables that perfect, glossy finish—is made from the excretions of Kerria lacca insects that are native to Thailand.%26quot; Read More|||glossy finish—is made from the excretions of Kerria lacca insects that are native to Thailand. Again, vegetarian lobbyists have urged the FDA to require that labeling indicate if fruits and vegetables are coated with an Read More|||Shellac (shiny coating on fruits, hard coating on jelly-beans) this is made from the excretions of Kerria lacca insects. FYI excretion means leaving the body…urine, feces, or sweat. The kicker in this to me is vegetarian lobbyists are Read More|||What it is: Shellac is ground Kerria Lacca Insects native in Thailand. * Gelatin – This is often used as a thickening agent in many packages. Is in icecream, gummy bears and worms. What it is: There have been many rumours about Gelatin; Read More|||Whenever you eat jelly beans.. you%26#39;re actually eating bugs. They put in this ingredient called, Shellac, which makes the jelly bean shiny and shit. Shellac is made from excretions from Kerria lacca insects that are native to Thailand. Read More|||La gomme laque est la seule résine naturelle produite par un animal, la cochenille femelle du genre Kerria (lacciferidé). La principale espèce productrice de gomme laque est Kerria Lacca aussi connue sous le nom de cochenille à laque ou Read More|||Two common members of that family are Tachardia lacca and Kerria lacca. The resin is a secretion from the female deposited on the bark of trees. Most of the shellac harvested in the world comes from Thailand and Southeast Asia. Read More [...]

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