Along
the Susquehanna River Trail
By John Capwell, Resident Biochemist and Former Botanist
Wood acoustic instrument manufacturers are awaiting the beginning of the spring harvest season of Toxicodendron radicans along the Susquehanna River. Manufacturers of guitars, autoharps and dulcimers eagerly await this harvest and hope that it will be a good one this year. The late spring end of April and May produce large quantities of the resin, otherwise known as urushiol. The quality of the urushiol is also affected by humidity; and the higher the humidity the better. Obviously those months are higher humidity months than later months. High humidity increases the water content of the urushiol, which means that it mixes better with the other ingredients in the lacquer and more rain produces larger volumes of the urushiol. The process of collecting the resin, developed centuries ago in Southeast Asia, is not unlike collecting maple sap for maple syrup since the urushiol is stored in the roots of the dormant plant. The vine is lanced and the sap is collected over a series of days and then sold to the lacquer manufacturer.
The resin accounts for approximately 20% of lacquer contents; water is the largest ingredient in the lacquer; and, some of those other materials are used to provide the desired color. The sap represents the key ingredient of the lacquer since it polymerizes, forming a plastic-like shield on the wood. This resin contains a ligase enzyme, laccase. The urushiol will undergo oxidation by oxygen; and, the oxidized components link up to form polymer chains. These polymer chains create a smooth finish that protects the wood.
This finish not only is beautiful but is also functional. It will protect the wood from acids as well as moisture. Since moisture changes the tonal quality of the wood, preventing moisture penetration is essential. This lacquer is also a surface finish and does not penetrate the wood, which means it maintains the integrity of the surface. Manufacturers not only want to protect the wood, they also want something that will be aesthetically appealing and the urushiol lacquer can take on a wide variety of pigments to meet that need.
The only downfall to the urushiol lacquer is its inability to withstand any alkaline substance. And that inability is the key to working with this substance. Spraying your clothing and exposed skin with a 50/50 mix of water and ammonia, never mind the smell, will prevent you from acquiring the infamous rash. Oh, I did forget to mention the common name for this plant? Well suffice it to say “leaves of three, let it be” should not stand in your way of making some extra pocket change on weekends.
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