Resins

The term natural resins usually refers to plant products consisting of amorphous mixtures of carboxylic acids, essential oils, and isoprene-based hydrocarbons; these materials occur as tacky residues on the bark of many varieties of trees and shrubs. In addition, natural resins have also come to describe shellac, which is a natural, alcohol-soluble, flammable material made from deposits on tree twigs left by the lac insect in India; amber, which is a fossilized polymeric material derived from a coniferous tree; and natural liquid substances such as linseed and similar drying oils.

Vegetable-derived natural resins generally fall in one of four categories:

1. Rosins, which are resinous products obtained from the pitch of pine trees. Rosins are used in varnishes, adhesives, and various compounds.
2. Oleoresins, which are natural resins containing essential oils of plants.
3. Gum resins, which are natural mixtures of true gums and resins including natural rubber, gutta percha, gamboge, myrrh, and olibanum.
4. Fossil resins, which are natural resins from ancient trees that have been chemically altered by long exposure. Examples of fossil resins include amber and copal.