Shellac is a natural resin made from the secretions of the lac beetle. It is primarily cultivated in India, where it is harvested from trees. It is a natural thermoplastic; a material that is soft and flows under pressure when heated but becomes rigid at room temperature. Shellac comes in various forms and colours including lemon, bleached, and unbleached. Shellac has been used traditionally in varnishes or coatings for furniture. Today, shellac is used in food preservation, perfumery and varnishes. It is sold as a solid, which can then dissolved in a solvent, such as alcohol prior to use.
Shellac is an important additive in the food industry, especially in the confectionery industry where it is commonly known as confectioner’s glaze; used as a natural glaze to add shine and texture. The resin also provides a barrier against moisture, humidity and high temperatures. It maintains colour stability and prolongs shelf life while preventing products from sticking together once packaged. It is used widely on food items such as chewing gum, sweets and even coffee beans.
It is used extensively in the perfume industry. Consisting of approximately 35% of α-Aleuritic acid, which is the starting material in the preparation of musk aroma. In order to obtain the acid, the resin needs to undergo an alkaline hydrolysis. Aleuritic acid is a critical component in the synthesis of macrocyclic fragrance chemicals such as ambrettolide.
In the varnish industry, shellac can be used as a wood finish. It adheres well when applied to clean, wax and oil free surfaces, producing a strong bond. Shellac is naturally UV-resistant and does not yellow or darken with age. It is a tough, durable finish that is less brittle than lacquer and more water resistant.
Shellac is a non-toxic organic compound. The Vegetarian Society considers it a vegetarian product, as the final product does not contain any of the lac beetles. The female beetle produces shellac to form a cocoon around her eggs. Once hatched, the insects leave the cocoon, at which point the resin is harvested. This relationship between farmers and the beetles, much like beekeeping, can be seen as conservation as it incentivises farmers to protect forests, which would otherwise be cut down for crop cultivation. This maintains biodiversity and stores carbon, whilst providing an income for local communities.
Although still used in traditional applications like varnishes, shellac has the potential to be used in high-tech applications. The University of Freiburg discovered that the resin can be used to produce low-cost and biodegradable microfluidic systems. Microfluidic technologies enable low-volume analysis of chemicals and reagents. They are a cost effective alternative to traditional analysis methods which often require larger samples.
Shellac has also been used to build biocompatible organic field-effect transistors (OFETs), which could pathe the way towards biodegradable electronics. OFETs are being heavily researched for their potential to produce light-weight solar-powered chargers, and many other applications.