Cork up one end of the tube, heat the point, see [A in Fig. 90], where you want the hole and then stick the other end in your mouth and blow gentle puffs in it until a little bulb is formed. When the bulb is cold take a file and gently crack the thin glass and trim it away; now heat the tube around the edge of the hole again until the glass begins to run when a round smooth hole will be produced as shown at [B].
Fig. 91a. welding two tubes together. b. making a T tube
To Join Two Tubes of the Same Size.
—Put a cork into one end of one of the tubes and hold the other end in the flame as well as one end of the other tube as shown at A in [Fig. 91].
Let the ends of the tubes get hot enough to melt but not thicken; now press the melted ends together hard enough to make them stick together but not hard enough to make them form a thick ring.
Fig. 92a. a regular blow-pipe
To make a good job you should now use a pointed flame and heat the juncture all around red hot and blow into the open end of the tube to spread the glass a trifle. While you are blowing keep turning the glass in the flame to make the joint nice and smooth.