Canada Balsam - Versatile Natural Resin for Artists and Opticians

Canada Balsam is the pale yellow oleoresin with a faint greenish cast of the balsam fir tree. It 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.

Origin

The name “balsam fir gum” is mainly used in North America. In Europe, the product is called “Canada Balsam.” It is also 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 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.

The most common adulterant of Canada balsam is either colophony (rosin) or crude turpentine. The best method of detecting colophony is to drive off the essential oil by prolonged heating on a water bath, leaving the dry resin to be examined. In the case of pure Canada balsam, this dry resin will be found to have an acid value of about 120 to 125, while colophony has an acid value of about 165. Hence, an acid value of over 130 indicates the presence of added colophony or crude turpentine. The presence of these adulterants can, according to E. Dietrich, be confirmed by the Storch-Morawski reaction, but, in the author’s opinion, this is incorrect and cannot be relied on.

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. There is also a true Oregon balsam, which is the oleoresinous exudation from the trunk of Pseudotsuga mucronata. This balsam yields a considerable quantity of essential oil, which can be characterized by its mainly consisting of laevopinene. The factitious Oregon balsam of the above description contains the same proportion of solid resin as pure Canada balsam, and the physical characteristics of the two substances are as nearly as possible the same. However, detecting such adulteration is possible by separating the essential oil and the resin and examining each separately.

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 is 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 also used as an ingredient in oil varnishes, sometimes to dissolve more insoluble resins such as amber.

Storage

To retain its essential properties, containers of balsam fir gum must be kept closed and stored in a cool, dark place. Canada balsam can easily be kept for several years in this manner.

Cleaning

To remove fir gum from clothing, apply strong cleaners, such as Pinesol, Lestoil, or WD-40 spray lubricant, then wash the article as usual.

To clean fir gum from tools, containers, and hands, apply a small amount of vegetable oil, margarine, or butter to the article or hands. These will quickly dissolve the fir gum. Then wash with warm water and soap.

Uses

Canada balsam is a plasticizer for varnish and paint. It can be used as varnish when diluted with a small quantity of denatured alcohol, lavender spike oil, or spirits of gum turpentine. The resin can also be mixed with drying oils (linseed and walnut oil) and other resins (copal and damar) dissolved incompatible solvents.

Canada balsam is used to prepare microscope slides and high-precision optical lens assemblies. Balsam fir gum is used for optical lenses because, when dissolved in an equal volume of xylene, its refractive index is almost the same as that of glass.

Packaging

2 fl oz, 4 fl oz, and 8 fl oz glass bottles
Former packaging, which may still be available in some locations: 250 mL and 100 mL glass bottles

*Standard deviation of three samples.