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HOW TO BLOW, ETCH, BORE AND GRIND GLASS
DESCRIPTION: THIS REPRINT OF AN EARLY 1900'S BOOK
CONTAINS INFORMATION ON WORKING GLASS BY HEAT AND
AUTHOR: PAUL N. HASLUCK
MANIPULATING GLASS TUBING.
THE materials used for glass-blowing are neither many nor expensive, all that are requisite being glass tubing in the diameters shown by Fig. 27, glass rod (Fig. 28), a sharp triangular file, a triangular too] of sheet copper mounted in a wooden handle (Fig. 29), pieces of charcoal sharpened to the shape shown in Fig. 30, and a small piece of beeswax.
There are several kinds of glass tubing made- soft soda glass , lead glass, and hard glass, the first-named being the best fitted for ordinary work. Good glass tubing should be free from bubbles, knots, and parallel lines ; when scratched with a file and broken, it should leave a straight end ; when brought into the flame it should not crack, nor become opaque, nor become covered with a fine powder.
In using the blowpipe if the gas be turned on only slightly, so that a small flame is given on blowing gently, a long, fine-pointed, very hot flame will be obtained ; with this, only local heating of an object is
possible (Fig. 31). This flame may be called the small flame. On admitting more gas and air, a large non- luminous flame results, which, though not so hot as the last, heats more gradually, and over a much greater area. This flame is the one most often used, and may be called the large flame (Fig. 32).
By ceasing to blow, a large, luminous, smoky flame is obtained, which is very useful for annealing hot glass; it cools objects gradually, and covers them with a non-conducting coating of carbon or soot, which protects them from currents of cold air. This flame may conveniently be styled the smoky flame (Fig. 33).
In cutting the smaller sizes of tubing make a clean file mark partly round the tube at the point to be severed, take the tube in both hands, place a thumb upon each side of the mark (Fig. 34), and bend slightly in a downward direction; the tube should sever cleanly. Large sizes, about 1/2 in. up to 3/4 in., may be cut by making a file mark as before, and bringing this part down on the edge of the bench sharply. For tubes over 3/4 in., it is necessary to place a piece of red hot glass rod on the file mark. Treated once or twice in this way they generally sever; if not, a drop of water will produce a crack which may carried around by judicious use of the hot rod.
In bending tubes with an ordinary gas jet, have a flame about 1 1/2 in. wide; hold the tube on each side of the flame at the tip of the bright portion (Fig.35), turning it round all the time, so that it may be equally heated. When the glass commences to soften, apply a very gentle bending force in the direction to produce a curve like that at Fig. 36, and not as at Fig. 37, which is badly made, and very liable to crack. During the heating, the tube will have become coated with a deposit of soot. This is a bad conductor of heat, and, if not removed, will allow the glass to cool slowly. Place the tube resting against a block of wood, so that the bend may not come in contact with any cold surface. When cold, proceed to bend the other end slightly. The end which is being heated in the flame cannot be held, so when the glass is soft enough, give it a touch with a piece of charcoal to bring it to the required shape allow to cool again...
TABLE OF CONTENTS:
1. Apliances used in glass blowing
2. Manupulating glass tubing
3. Blowing bulbs and flasks
4. Jointing tubes to bulbs, etc; forming thistle funnels
5. Blowing and etching fancy glass articles; gilding and
embossing sheet glass
6. Utilising broken glass apparatus; boring and riveting
7. Hand-working of telescope specula
8. Turning, chipping, and grinding glass
9. The manufacture of glass