Fig. 93. first steps in blowing a glass bulb
A. Drawing out the tube.
B. Forming glass rings on the tube.
Then heat a small part of the tube in a large, or brush flame, turn the glass in the flame all the time until it is soft and then press on both ends to make the glass thicker at this point. Do the same thing above the ring thus formed, and so on until you have several rings of glass as shown at [B], which are thick enough to make the sized bulb you want.
Fig. 93c. making a thick ring of glass
Next heat the narrower parts marked a a a a and blow gently and press gradually on the ends to make the thick rings melt and flow together into one large ring of thick glass as shown at [C]; and in doing so be mighty careful that the walls do not cave in.
Now melt and seal off the tail and heat the whole bulb in as large a flame as you can get and at the same time turn the tube till the rings run together. At this instant take it from the flame and, still turning it, blow into it with a few little quick blasts until you get the size and shape you want as shown at [D].
Fig. 93d. last step in blowing a glass bulb