Shellac

Shellac is a natural resin secreted by female insects.

This substance is chemically similar to many synthetic polymers. Because of this, it can be considered a natural form of plastic. It is mainly composed of several organic acids. These include aleuritic acid, jalaric acid, and shellolic acid. It also contains natural waxes. Shellac is a versatile material used in many different industries. It serves as a wood finish, a food glaze, and even a component in medication.

The production of shellac begins with the female lac bug, known as Kerria lacca. These insects live in the forests of India and Thailand. They crawl along tree branches and suck the sap from the trees. As they move, they excrete a substance called sticklac. This material forms tunnel-like tubes on the bark. While these are sometimes called cocoons, they are not true cocoons in a biological sense.

To collect the resin, workers scrape the sticklac from the tree bark. This raw material contains bark shavings and insect remains.

Processing the raw material requires heat and filtration. The scraped material is placed into canvas tubes that resemble long socks. These tubes are heated over a fire. The heat causes the shellac to liquefy. As it melts, the liquid seeps through the canvas. This process leaves the bark and the bugs behind in the cloth. The resulting thick, sticky shellac is then dried into flat sheets or hard buttons. These are broken into flakes to be sold.

Users typically prepare shellac by dissolving it in alcohol. Most people use ethyl alcohol or denatured ethanol. The concentration of the liquid is measured in "pound cuts." This term refers to how many pounds of flakes are dissolved in one gallon of alcohol. For example, a 1-lb. cut contains one pound of shellac per gallon. Most commercial mixes are sold at a 3-lb. cut. Because liquid shellac has a limited shelf life of about one year, it is usually sold in dry flake form.

Shellac has a long and varied history of use. The ancient Indian epic poem, the Mahabharata, describes a palace coated in dried shellac. By the year 1220, artists in Spain used shellac as a binding agent for pigments. In the 17th century, it became popular in Europe as a sealing wax for letters. During the 20th century, it was a dominant wood finish in the Western world. It was often used as an "orange shellac" to stain and protect wood cabinetry.

In the past, shellac was essential for the music industry. Most 78 rpm gramophone records were made from shellac compounds. Between 1921 and 1928, tons of shellac were used to produce 260 million records in Europe. In the 1930s, it is estimated that half of all shellac production went toward making these records. Eventually, vinyl replaced shellac for record making. Shellac also has unique uses in the arts. For example, ballet dancers have used it to stiffen the toe boxes of their pointe shoes.

Shellac comes in many different colors. These range from a very light blonde called "platina" to a very dark brown called "garnet." The specific color depends on the type of tree the bugs live on and the time of harvest. Naturally, shellac contains between 3% and 5% wax by volume. Some manufacturers create "dewaxed shellac" by removing this wax. This allows other coatings, like paint, to stick to the surface more easily. Shellac is also highly UV-resistant, meaning it does not darken as it ages.

Today, shellac is used in specialized ways. While modern plastics like polyurethane have replaced it for floors, shellac is still used by luthiers. They use it for "French polishing" fine acoustic stringed instruments. It is also used as a confectioner's glaze on candy. It can even be used to preserve harvested citrus fruit. One of its best features is how it repairs itself. Unlike some synthetic coatings, a new layer of shellac will merge and bond with old layers. This makes touching up damaged areas very easy.