Resins

David S. Seigler Department of Plant Biology University of Illinois Urbana, Illinois USA

OUTLINE: RESINS AND TURPENTINE Importance o Turpentine o Naval stores o Adhesives o Varnishes Incense Antiseptics o Amber Botanical

Properties o Lipid soluble Economics Isolation

Reading CHAPTER 10 IN THE TEXT, p. 257

Introduction Resins have played an important role in many cultures. They are part of paints, incense, and ship caulking. Most have been replaced by synthetic materials, whereas a few have not been. In the plant, resins are actively synthesized and secreted into specialized canals or ducts. Resins are involved in wound responses or in limiting herbivory to the plants.

In contrast to gums, resins are insoluble in water. Most gum plants came from the Old World; the same thing is true for resin plants, although a few important ones came from the New World as well. One of the most ancient uses of resins was as part of incense. Most resins are hydrocarbon-like and burn. Two classical resins used for this purpose were frankincense (Boswellia carteri, Burseraceae) and myrrh (Commiphora myrrha, Burseraceae).

Myrrh, Commiphora aff. Myrrha, Burseraceae Courtesy Dr. Dorothea Bedigian

Myrrh, Commiphora aff. myrrha, Burseraceae S. Colenette. An Illustrated Guide to the Flowers of Saudi Arabia. 1985

Boswellia carteri, Burseraceae National Geographic

Boswellia carteri, Burseraceae National Geographic

The value of these resins in the time of Christ is illustrated by the fact that the wise men brought them as gifts along with gold. Both plants are native to East Africa (Ethiopia). They were early products of trade. They are removed as drops from the trees. Neither is especially valuable today. Many of these resins were also used for embalming by the Egyptians.

Other important resins are mastic and lacquer (not to be confused with liquor) [(or shellac)]. Mastic comes from Pistachia lentiscus, Anacardiaceae. Sometimes used for chewing gum.

Lacquer (one kind) comes from Rhus verniciflua, Anacardiaceae. Both are used for sealing articles such as wood carvings. The Chinese and Japanese made an art form out of use of this type of finish. Many people are highly sensitive to the Japanese and Chinese ones as that type of lacquer contains compounds similar to those in poison ivy.

Copal and dammar Copal (from Copaifera or Hymenaea species and from Agathis, Araucariaceae) are used to coat art work, e.g., oil paintings. The resin from Copaifera is sometimes called copaiba balsam. Dammars from members of the family Dipterocarpaceae (especially Shorea species) are used in a similar manner.

Aceite, Copaifera sp., Fabaceae

Hymenaea coubaril, Fabaceae T. D. Pennington & J. Sarukhan, Arboles Tropicales de Mexico, 1968

Shorea robusta, Dipterocarpaceae Indian Subcontinent

Trees of Dipterocarpaceae in Bogor, Indonesia

Other natural resins are used in adhesives, soaps, sizing, floor coatings, pharmaceuticals, fireworks, incense, leather finishes, and lithography. Resins are used in varnishes, but have largely been replaced by better quality synthetic materials.

Balsam-of-Peru Balsam-of-Peru resin comes from a tree, Myroxylon balsamum, Fabaceae or Leguminosae that grows mostly in Central America. Most of the supply comes from El Salvador. This resin is used for medicinal purposes as an antiseptic, as a fixative for perfumes and in soaps.

Balsam-of-Peru, Myroxylon balsamum, Fabaceae or Leguminosae

In the old days, it was shipped through the port of Callao in Peru. The tree is about 100 feet tall. The collectors cut out a small panel from the tree and stuff it full of rags. Then, they burn and bruise the tree above the cut open area. Later, they collect these rags and remove the resin.

Turpentine and rosin Turpentine is tapped from a number of trees. In the U.S., the most important one was Pinus palustris, the long leaf pine. The material obtained is then distilled to remove the volatile essential oils that are called "spirits of turpentine". These are still used as a solvent, but have largely been replaced by petroleum- derived hydrocarbons.

Long leaf pine previously tapped for terpentine

Terpentine tapping in India from Pinus species Courtesy Dr. Ted Hymowitz

Tapping now often involves application of plant hormones, sulfuric acid or the herbicide paraquat to improve yields. The wood is used after the trees have been tapped extensively, but is not of as good quality. Much turpentine is derived from tall oil from the paper industry. The distillation is now carefully controlled and done in more sophisticated plants.

The remaining material (made up largely of diterpene acids) is called rosin. Rosin is used for violinist bows, for boxing gloves, and baseball pitchers. Rosin is also used in printer's inks, paper coatings, soaps, varnishes, sealants, tin can linings, and plywood manufacture.

Rosin used to be used to make linoleum. This material has almost completely been replaced by vinyl flooring. A number of adhesives contain rosin. Others are purely synthetic. The crude material sticks to everything, including the worker's heels and they used to be called "tar-heels". The name stuck in North Carolina.

Naval stores Resins from gymnospermous trees (especially Pinus species) have been used for millenia to caulk ships. This was done in Europe and later in the U.S. These materials were also used to waterproof containers of various types in the Old World, but also by the American Indians.

Amber Amber is fossilized rosin. The source in the temperate areas of the world tends to be gymnosperms whereas that in the tropics tends to be legumes. Amber is widely used for jewelry.

Lac used to make shellac is actually an insect product. The insects live on several trees of the Fabaceae (Butea, Cajanus, Acacia), Rhamnaceae (Zizyphus), Sapindaceae (Schleicheria). The insect (Laccifer lacca) is a scale insect. The reddish translucent material from the insect (called "seed lac") is treated with minerals and other resins to make "shellac". Shellac is used in high polish interior spirit varnishes and waxes. Most of it comes from India. Lac