Pine Trees Are Not Just for Squirrels

When writing about the case study of this scientific journal that talks about the varnishes on post-Byzantine religious icons and the recipes of the varnishes, I discovered there was an interesting story behind these varnishes and pine trees. These varnishes that was used as a clear “cover paint” to preserve these religious painting were mainly made of vegetable oil and resins that came from pines trees and cypresses, or the conifer family in botanical terms. This painting technique was used predominantly in the post-Byzantine periods (sixteenth to nineteenth centuries). One of the ways to produce these varnishes is to dissolve heated conifer resin in hot oil and Viola! Those were the clear “stuff” we see, I guess on multiple art works we encounter in numerous museums?

            That was when I realize how useful pine trees can be, other than making varnishes for conservation of ancient artworks. Generally, the pine trees and cypresses and all the look-alikes, all come from the coniferae family. There were other related species with way too complicate Latin names; I’ll skip those. So in China and our ancient botanical books, the pine resins were made out of boiling the oil in the barks of pine trees. If the trees were very old, the resin can be naturally obtained from the old barks. To ancient Chinese people, pine resins, also called colophony, had significant medical values.  They were the “fat” of the tree. The drugs made out if colophony can treat skin radishes, all kinds of insect bites and many skin problems if applied on skin. If eaten, they could be pain killers, or “put down the fire in your body”. The “fire” was a pretty exclusive concept that only Chinese people understood, but basically the symptoms were feeling burned inside, dry skin, easy to nose-bleed and always feeling like you ate tons of spicy chili.

            Main chemical compounds responsible for the therapeutic values of pine resins were abietic acids and abietic anhydride. Abietic acids, an organic compound present primarily in pine resins, could be an enzyme inhibitor. They were insoluble in ethers, acetones and alcohols. They could oxidize over time to produce dehydroabietic acids, then the ultimate degradation product retenes. The stability was increased by heating, like the “varnishes”. Moreover, some people are allergic to abietic acid (contact), hence all the resin products. Traditionally, abietic acids were used on instruments to increase the friction of bows.

            So these pine trees aren’t just for squirrels to play around with… and those pretty pine nut for Christmas… Pine trees actually mean a lot and super useful in industrial and medical uses!

abietic acid

Resources:

http://www.jstor.org/stable/25487716?seq=2

http://dict.youdao.com/search?q=bk%3A%E6%9D%BE%E9%A6%99&keyfrom=wiki.related&le=eng#q%3Dbk%253A%25E6%259D%25BE%25E9%25A6%2599%26keyfrom%3Dwiki.related%26le%3Deng