Smoothness and exactness are the two things for which the beginner must constantly strive in glass-blowing, and they are only attained by a careful attention to the details of manipulation, with a steady hand and watchful eye. Every move must count, and the exercise must be finished with a minimum of reheating and retouching, for the best results.
CHAPTER III
ELEMENTARY EXERCISES
EXERCISE NO. 1
Joining Two Pieces of Tubing, End to End—First Method
This exercise is most easily learned on tubing with an exterior diameter of 1⁄4 inch, or a little less, having moderately heavy walls. A piece of such tubing is heated before the blow-pipe at a point ten or twelve inches from the end, and there drawn out to a capillary as previously described (page 9). The capillary is sealed off about two inches from the main tube, and the latter is cut near the middle. Care should be taken to get square ends where the cut is made (page 7). The flame is now so regulated that it is a little broader than the diameter of the tube, the sealed half of the tube taken in the left hand and the other half in the right. The open end of the sealed part and one of the ends of the other part are now held in opposite sides of the flame, inclined at a slight angle to one another as indicated in Fig. 5, and rotated and heated until the surfaces of both ends are just softened. The two ends are then carefully and quickly brought together (a, Fig. 6), removed from the flame and pulled apart a little, to reduce the lump formed at the joint as much as possible, as indicated in b. The joint is then tested by blowing into the open end of the tube to see if it is tight. If so, the flame is reduced to half or less than half of its former size, and the joint heated in it, holding the tube and continually rotating it as directed in the last chapter (page 13).
Fig. 5.—Softening ends of two pieces of tubing.