Glass Tubing and Rod

Crude glass rods were originally drawn directly from melts by simply dipping the end of a metal rod into the melt and pulling upward. These rods were of poor quality, with variable diameters and cross-sectional shapes. The rods were often reworked by hand to improve their quality and stretched to form the desired diameter. Tubing was formed by using a blowpipe and forcing a bubble to travel down the rod as it was pulled from the melt. 

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Cutting. — Glass tubes and rods are cut as follows Determine the length needed, lay the glass on the table, and with a forward stroke of a triangular file make a short but deep scratch where the glass is to be cut. Grasp the tube in both hands, one on each side of the mark, and hold... 

The former suppliers, however, make substantial additional charges for glass tubing and rod kept in their stores. It is always worthwhile to inquire about costs and delivery dates before placing orders of any size with laboratory furnishers, and to compare them with similar estimates made by the tubing and rod makers or distributors. 

FIG. 6.8. Alternative methods of making a knife mark on glass tubing and rod. 

The glass tubing and rod required for an elementary glassblowing course will depend on the personal choice of the instructor. The following list is set out as a guide. 

Glass tubing and rod test-tube brushes, cloth, matches, labels... 

Phoenix, also, is a borosilicate glass made by the British Heat Resisting Glass Co. The linear expansion coefficient (50-450°Q is 3-24 X 10" . Tubing and rod are supplied in a wide range of sizes. The tubing is made with either standard wall or heavy wall. 

I il a soda-lime-silica glass, containing magnesia and boric oxide 1 than 1 per cent), made by the General Electric Co. It is often ibed as GEC X.8. or simply as X.8. The linear coefficient of Jial expansion between 20 and 350°C is 9-65 0-10 x 10-. This I il available as tubing and rod in a wide range of sizes. 

This change is best observed by sealing a small quantity of the compound in a thin-walled glass tube and slowly heating it in a water bath, using a thermometer as a stirring rod. 

Obtain the salt in small crystals and carefully dry them. Seal a small sample in a thin-walled glass tube and determine the transition point by using the tube as a stirring rod in a beaker of water that is being heated. When approaching the transition point, regulate the flame so as to raise the temperature of the water very slowly. 

A reasonably dust-free cabinet stocked with a variety of standard wall tubing, heavy-walled capillary tubing, and rod A ring stand and clamps with woven-glass-covered fingers Surface-mix bench burner for large items... 

The above figures refer to the best quality machine-drawn tubing and rod. Special glasses are often made in relatively small quantities the tubing will then be hand drawn and the dimensional tolerances will be greater. 

Precision bore tubing is normally made from borosilicate glass, but is also obtainable in other glasses including silica. Tubing and rod can also be obtained with the outside diameter ground to a specific size accurate to +0.0005 in. (+0.013 ram), and concentric with the axis. 

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