A Thousand Year Old Coating: The Historical Origin of Biobased Coatings

In 1977, the Yuyao Hemudu Site began the second round of excavation under the auspices of the Zhejiang Provincial Cultural Administration Commission and Zhejiang Provincial Museum. During the excavation work, archaeologists discovered an unusual vessel. Gently wipe away the soil on the surface of the vessel, revealing its true nature: it was a slightly shiny, vermilion red wooden bowl. After careful observation, all archaeologists showed an excited expression: the vermilion color on the outer wall of the vessel was not the color of the wooden material itself, but was formed by a layer of paint applied to the outer wall. This discovery proves that at least five to six thousand years ago, our ancestors used coatings to decorate the surfaces of household utensils. After chemical methods and spectral analysis, it was found that the coating on the surface of the wooden bowl is a natural lacquer known as "national lacquer".

 

                                                           

 

The vermilion lacquer wooden bowl has a history of at least 5000-7000 years, but it is not the oldest lacquer ware discovered. The lacquer bow unearthed at the site of the cross lake bridge has a history of at least 8000 years after carbon-14 measurement.

 

Raw lacquer, also known as "national lacquer" or "large lacquer", is a pure natural liquid coating made in a very complex way: lacquer cutters choose to go out in hot and humid weather to cut lacquer. They climb up tall lacquer trees, use sharp objects such as shells and knives to cut open the bark of the tree, and pour milky gray, sticky tree sap emitting a light acidic aroma into small barrels. After coming into contact with air, this gray white liquid gradually turns golden yellow, blood red, and finally turns brown, becoming a viscous liquid used in the manufacture of various lacquerware.

 

Lacquer plays an indispensable role in Chinese lacquer art. The painting process originated in the Neolithic Age and was mainly used to make daily necessities and sacrificial offerings. After thousands of years of exploration, the painting process has become increasingly mature. During the Han and Wei dynasties, exquisite wooden objects coated with lacquer, along with silk, accompanied by the sunset and yellow sand for countless days and nights, were exported to the Eurasian continent and were one of the most important trade items on the Silk Road at that time. Chinese lacquer painting reached a very high level in the Tang Dynasty, and was given and rewarded to other countries as a national gift. This kind of lacquerware with a simple and natural appearance but exceptionally exquisite interior has had a profound impact on Japan and Southeast Asian countries, and in the future, it has contributed to the formation of Japanese lacquer art, becoming the most important component of Japanese lacquer culture.

 

                                        

The Southern Song Dynasty carved red double dragon peony pattern rectangular plate, measuring 27.1 cm in length and 13.2 cm in width, is currently in the collection of the Kamakura National Treasure Museum in Kanagawa, Japan. A large number of lacquerware have been collected by other countries due to poor preservation and war, which is regrettable.

 

However, since modern times, with the gradual popularization of the modern paint industry, the disadvantages of raw lacquer have gradually become apparent: a lacquer tree that can be used for cutting lacquer takes nearly ten years to become mature, and a lacquer tree can only produce a few kilograms of raw lacquer in its lifetime; When cutting paint, there are high requirements for personnel (the vast majority of people will experience allergic reactions when exposed to partially dried natural lacquer, so it is necessary to screen personnel who are not allergic to lacquer when cutting paint); Incorrect paint cutting process can lead to the death of lacquer trees, resulting in significant economic losses. But the most important thing is that the use of wood in architecture is also decreasing year by year. This ancient paint, which is more suitable for use on wood materials and has painted thousands of years of Chinese civilization, has gradually lost its luster in the past, and has become an inconspicuous supporting role in a wide range of paints.

 

 

                                      A lacquer cutter with white temples in the deep mountains of Bijie, Guizhou

Until recent years, decoration styles such as "silent wind" have gradually entered people's vision. This decoration style advocates simplicity and quietness, aiming to present a pure aesthetic feeling. In its design elements, a large number of furniture and decorations made of logs are used, giving people a sense of returning to the basics. At this point, people realized that although wood is not suitable as an industrial material due to its complex organizational structure, uneven material, porous, hydrophilic swelling and contraction characteristics, its natural beauty is incomparable to other building materials. Wooden homes have once again gained people's love and become a popular choice for decoration in recent years, and the use of wood coatings has also shown a gradual growth trend. More environmentally friendly "bio based" coatings have also become a research hotspot. As the ancestor of "bio based" coatings, lacquer has regained its place in the manufacturing of high-end furniture and artworks.

 

 

The decoration style of 'silent wind' embodies the philosophical conception of nirvana and impermanence in Buddhism.

 

In addition to solid wood, the wood products currently used also include man-made boards (plywood, medium density fiberboard and particle board). In order to save on the use of wood and improve its utilization rate, we usually make plywood from wood and use it for testing wood coatings. In the testing of wood coatings, the following standards should be met: meeting the latest standard GB/T 15104-2006 for inspection substrates, the panel surface should be flat, smooth, free of oil stains, joint marks, etc., with a moisture content of less than 12%, and have been polished. The corresponding testing items and substrate are as follows:

Substrate

Testing items

standard

150x70mm light colored veneer plywood

Constructability, dryness, appearance, polishing, adhesion, water resistance, alkali resistance, alcohol resistance, and pollution resistance

GB/T 23995 Solvent based Alkyd Wood Coatings, GB/T 23997 Solvent based Polyurethane Wood Coatings, GB/T 23998 Solvent based Nitro Wood Coatings, GB/T 23999 Waterborne Wood Coatings

HG/T 3655 UV Curing Wood Coatings, etc

150x150mm light colored veneer plywood

Resistance to dry heat

one hundred and fifty × one hundred × 10mm beech (Shuiqinggang) solid wood flooring

Impact resistance

 

The foundation of China's bio based coatings is laid by the standard of T/CSTM00447-2021 Bio based lotion Interior Wall Coatings organized by CSTM Coatings and Pigments Standardization Technical Committee in 2020, which stipulates the requirement of bio based carbon content ≥ 20%.

 

At present, more and more coating companies are using bio based technology to develop high environmental performance bio based coatings. However, bio based coatings have not yet been widely used in industry and are still in their early stages. However, they are still an important step towards sustainable development of coating processes. The development of bio based coatings is not only conducive to improving the market competitiveness of enterprises themselves, but also makes due contributions to environmental protection and resource conservation, thereby establishing a good social image for the coating industry.