Canada Balsam is the pale yellow oleoresin from the the balsam fir tree. It is dries to a clear transparent film. It is used as a plasticizing resin for varnishes and paints. Canada balsam is amorphous when dried. Since it does not crystallize with age, its optical properties do not deteriorate. Although it needs to be stored in a cool, dark place.
The name "balsam fir gum" is mainly used in North America. In Europe, the product is called "Canada Balsam." It is also variously identified as turpentine, fir resin and fir gum.
Of all the species of fir in North America, the balsam fir (Abies balsamea) growing in Québec and New Brunswick, Canada, is the source of balsam fir gum or Canada balsam. It is a syrupy, greenish-yellow liquid that is drawn from small blisters on the trunk of the fir tree. Balsam fir gum is harvested between April and November, however, it is typical to harvest in warm weather, as the gum is more fluid during warmer temperatures.
There is a product sometimes to be found on the market under the name of “Oregon balsam,” which is not a natural product at all, but is a mixture of rosin and turpentine, closely resembling Canada balsam in appearance, and which is used to adulterate it frequently.
Canada balsam closely resembles Strasbourg turpentine in physical properties and composition. Strasbourg turpentine is obtained from the Abies alba, silver fir or European silver fir, and named after the trading center in Vosges. The Italians called it “Trementina di Strasburgo” or “di Alsazia.” It is a less viscous balsam used historically as a varnish (dissolved in spirits of gum turpentine) to provide special protection to easily decomposed pigments such as verdigris. It was used also as an ingredient in oil varnishes, sometimes to dissolve more insoluble resins such as amber.