Indications for pembrolizumab
8 10 月, 2020Introduction of Polyhexamethylene
6 11 月, 2020What is the use of shellac
The most common form of shellac is varnish (shellac) mixed with an alcohol base. However, shellac, a viscous light yellow resin, has to undergo many strange evolutionary processes in parasites before it is used to cover oak rocking chairs. This resin is mainly obtained from a South Asian insect called "Laccifera lacca", which is the only way to harvest this useful substance.
In fact, the history of dyeing old phonograph records or oriental carpets all began with this little insect. Hundreds of small insects crawled out of the eggs and scattered on a succulent plant or tree. They immediately stick their mouths to leaves or rhizomes to suck food and water, and their subsequent lives are parasitic on plants.
After this insect develops from a pupa to an adult, it will gradually excrete a viscous or waxy liquid and wrap itself into a cocoon. Because they are easy targets for predators, these insects separate and harden their skin to avoid attacks by birds or spiders. In India and Thailand, farmers let thousands of these insects inhabit trees such as long trees, butea and rain trees.
This unusual "crop" can last for a season until the male leaves the cocoon and the female lays new eggs. To harvest these crops, the shellac and other impurities on the raw materials of shellac must be washed away. After cleaning, filtering and processing, they become granular shellac, which is then refined and processed into shellac varnish and other products.
Raw shellac is yellow or orange, which is the color formed by the dye in the female ovaries. Some woodworkers prefer amber, and some products bleach shellac into a transparent sealant. In the past, shellac was used to tan leather, make records (before vinyl replaced it), and polish wooden floors. As early as the 3rd century, people also used shellac to dye fabrics. Since the 16th century, people began to develop this pigment into a sealant layer for wood.
Nowadays, shellac is also used to produce sustained-release capsules for oral drugs, yellow and orange food colors. Because it is non-toxic and edible, other artificial substances cannot replace shellac. Many carpenters still like to use shellac varnish because it protects the wood from UV damage. Despite the strong smell, shellac varnish dries quickly and is not dangerous after processing. It can be used for objects in contact with pets and babies, without worrying about poisoning.
