Canada balsam glass

Canada balsam is one of the oleoresms. It is obtained from the bark of Abies bciisamea, the common balsam fir of northern North America. Canada balsam, because its refractive index is so near that of glass, is much used in optical work and m preparing materials for examination with a microscope. 

If too much Canada balsam has been used, some of it usually spreads beyond the edge of the cover-glass, or on its surface. In this event wait until the balsam hardens, when it can be scratched off with a knife, and the surface of the glass cleaned with a rag moistened with turpentine oil or xylol. 

It consists of three pairs of cylindrical containers Ti and Ti, Tz and Tz, and Ts and Tz, which dip successively one into another. Each pair is narrower than the pair of cups beneath it. Ti and T are closed at the bottom, ground-glass plates being kept in place by screw-caps. The other pairs of cylinders likewise have glass plates cemented (preferably with Canada balsam) to the lower ends. The total height of the liquid column is determined by the distance from the bottom of the ground glass plates of Tz and Tz to the top of the plates which close cups... 

Canada balsam Ayellow-tintedresin used for mountiiig specimens in optical microscopy. It has similar optical properties to glass. 

The final step in specimen preparation is to mount the prepared thin section, replica, fibers, or particulate strew, usually on a standard 25 mm x 76 mm (lin. x3in.) glass slide, with a mounting material (mountant) (Canada balsam or its proprietary substitutes, glycerin, oils, aqueous liquids), and then to cover the preparation with a coverslip, a thin glass disk, or plate. 

Canada balsam n. Oleoresin, which exudes naturally from Pinus balsameUy the Canadian balsam pine. It is essentially a resin dissolved in an essential oil. When freshly exuded it is a viscous liquid, but it hardens on exposure. Its chief use is for cementing lenses and other glass objects, because its refractive index, 1.53, is near that for glass. It is also used in the manufacture of fine lacquers. 

Venice turpentine has been used in picture varnishes and as a tackifying resin in adhesives partly because it inaeases the flexibility of the film, though this effect will diminish as the monoterpenes evaporate. Canada balsam was widely used for mounting specimens on microscope shdes and as a glass adhesive, though again the evaporation leads to shrinkage and distortion. 

Others. Due to its ability to dry to a brittle, clear glass-like residue, Canada balsam (usually freed from volatile oil and dissolved in xylene) was extensively used as a cement for lenses and prepared microscopic slides. Its use in some balsam hair grooming products probably takes advantage of this property to stiffen hair and give it body. ... 

Figure 6. Polygonal texture in a cholesteric liquid (MBBA and Canada balsam) observed under natural light (a) coverslip level, (b) lower glass level, t. Translation defects (there are other unmarked translation defects in the micrographs). Scale bar 20 pm.

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