Laboratory manual of glass-blowing by Frary Francis C. (Francis Cowles) b. 1884

Author:Frary, Francis C. (Francis Cowles), b. 1884
Language: eng
Format: epub
Tags: Glass blowing and working
Publisher: New York [etc.] McGraw-Hill book company, inc.
Published: 1914-03-25T05:00:00+00:00

FIG. 10 —Blowing a bulb on the end of a tube.

30 LABORATORY MANUAL OF GLASS-BLOWING

Fig. 10, separated by thickened ridges which will be almost impossible of removal later and will disfigure the final bulb. This operation of heating, blowing and pushing together is repeated several times, until the cylinder becomes as long as can be conveniently handled (about 1 1/4 inches to 1 1/2 inches). If more glass is needed than is then contained in the cylinder, the latter may now be heated as a whole, and blown and pushed gently into a shorter cylinder of a slightly greater diameter, and more glass then added as before.

When enough glass has been collected for the bulb, it is all well heated and blown gently a couple of times, pushing the mass together as required, until a thick bulb like d, Fig. 10, is obtained. The tail must now be removed at the point indicated by the dotted line. To do this, a very fine flame is directed on the point where the tail joins the bulb, and the tube well rotated as the glass softens at that point. When sufficiently soft, the work is raised a little, so that the flame instead of striking the glass squarely at the point indicated passes below and tangential to it. The tail is now drawn off slowly, continuing the rotation, raising the work just out of the flame whenever the thread of glass drawn off becomes too thin, and lowering it again to the point where the flame just touches it when the glass stiffens a little. By this means the tail may be drawn off without leaving an appreciable lump behind, as indicated in e and/, Fig. 10. When as much of the extra glass has been removed as is practicable, the flame is brought to play squarely upon the little lump left, the last of the tail removed, and the lump heated and gently blown to a small excrescence on the main bulb. The whole end of the latter is now heated until it begins to shrink a little, and gently blown to make it uniform in thickness. The whole bulb is then heated in a flame of the proper size, so that it all may

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