The Methods of Glass Blowing and of Working Silica in the Oxy-Gas Flame (Paperback)

Excerpt: ...simultaneously blow and draw it into its final shape as seen at III. The side tube F should not be too near the end E. If, however, it is necessary to have them close together, the joint F must be very carefully annealed when it is made; it must also be very cautiously warmed up before the construction of the joint at H is begun, and must be kept warm by letting the flame play over it from time to time during the process of making the latter joint. A good joint may be recognised by its freedom from lumps of glass, its regularity of curve, and by a sensibly circular line at H, where the two tubes are united. 47 When the joint after annealing has become quite cold, the pin-hole at C on the inner tube may be closed, after removing the paper support, by warming the outer tube, and then directing a fine pointed flame through D on to C. And the end D of the outer tube may be closed in the ordinary manner, or a narrow tube may be sealed to it. As the end of glass at D will be too short to be held by the fingers when hot, another piece of tube of similar diameter must be attached to it to serve as a handle (see p. 35, Fig. 9 ). Blowing a Bulb or Globe of Glass.