Shellac - natural varnish used for hundreds of years to protect wood

The first material used to protect wooden furniture and musical instruments was shellac. As well as protecting furniture, it gave it that warm sheen that we now only see on old objects. The application was laborious and took a long time and many successive coats applied, but a beautiful surface with a deep gloss was obtained. However, despite the beauty, the strength of the film was not very good, which over time led to it being replaced by new, modern materials, preferred for their increased strength and speed of working. As a result, the old application techniques have been lost, with fewer and fewer people knowing how to protect wood in the past. But I think shellac is an important part of wood finishing and that's why I want to tell you more about it.

Shellac was the first material used to coat furniture and stringed musical instruments. It is thought that the Venetians were the first to use it in the 16th century. At that time, a new profession emerged, that of furniture painter. The painter was neither a painter nor a furniture maker. He only varnished furniture with shellac using a technique known today as French polish.

In the 18th century shellac finishing was much used in Victorian England to coat furniture made from expensive wood brought from the colonies. The heyday lasted until the 19th century, when oil and wax finishes appeared. However, expensive furniture continued to be made with shellac. In the early 20th century (1920s-1930s), however, it was almost completely replaced by nitrocellulose lacquer, which was very similar in appearance but could be sprayed on and easily polished.

Shellac is a resin secreted by the female of a beetle called lac (Keria lacca) that lives on trees in the forests of India and Thailand. The beetle feeds on tree sap and deposits the resin on its branches, making a tunnel.

The colour of the resin is different depending on the type of tree and the time of year it is secreted. It can vary from straw yellow to dark brown, orange, red or light brown. As a curiosity, it is said that it takes 100,000 to 300,000 insects to make one kilo of varnish.

When the resin is gathered from the branches, pieces of bark and even insects are taken. Everything is put into a sock-like cloth tube and heated. The resin melts and drains off, leaving the remains in the sock. The liquid is then poured into the thin film and left to harden. At the end the thin layer is broken up to obtain shellac flakes.

There is also the shellac "button" version, but it's all about how the resin was poured.

The varnish is obtained by dissolving the resin in industrial alcohol (denatured spirit). The varnish prepared does not last very long, which is why shellac is sold in solid form. If it is prepared it is best to keep it cold because high temperatures accelerate its deterioration. If the prepared varnish has been sitting for a long time, it should be checked before use. Pour a few drops and if it hardens immediately the varnish is good. If they remain sticky it can no longer be used. When you decide to buy ready-made varnish always check the date of manufacture and the guarantee. These must be written on the label. If they are not, do not buy the product.

The varnish naturally contains 3-5% insect wax. There is also a wax-free, purified (dewaxed) version for finishes that involve covering the shellac with another coat of varnish of a different nature or when the coats applied are thicker. If finishing with shellac only, unpurified shellac can be used. The waxed version turns whitish when dissolved in alcohol, but becomes transparent when dry.

The resin secreted by Keria Lacca is not only used to make furniture varnish. In the food industry it is used to give a shine to sweets and other foods, and in combination with wax to protect fruit transported over long distances (citrus fruit). In the past it was used to insulate electrical wires against damp or to make gramophone and patephone plates, but it was replaced with the advent of vinyl.

Shellac protects wood, blocks tannins and odour inside, is UV resistant and does not fade over time like other varnishes. When it dries it has a natural high gloss and silica is added to smooth it out. The lacquered surface is sensitive to water and alcohol, turning whitish, and is not very resistant to high temperatures, softening if a cup of hot liquid is placed on it. However, defects are easily repaired by simply applying varnish to the damaged area. The added varnish blends in perfectly and the defect disappears.

The method of applying shellac is called French polish. It consists of the successive application of many thin coats of polish in continuous, circular movements. As there is much to say about the method I will continue with a detailed description of howhow to get that unique shine.