_Blowing a Bulb or Expanding a Join._--Prolonged heating is necessary in order that the thick parts may be heated completely through. Blowing should take place by stages, in order that the thin parts, which tend to expand first, have time to cool. The thick parts can then be expanded by further blowing and thus a bulb or expansion of even thickness can be obtained. _Cutting Glass._--The most useful method for general use is by means of the file or glass-blowers' knife. Either file or knife must be kept sharp by grinding. Neither file nor knife should be used on hot glass. The diamond and wheel cutter are useful for cutting sheet-glass, and when the diamond is employed a singing noise is an indication of a satisfactory cut. _Leading a Crack._--A crack may be led in any desired direction by means of a bead of hot glass or a small gas flame. The glass which it is desired to crack should be heated at a point slightly in advance of the crack, which will extend in the direction of the source of the heat. _Turning Out the End of a Tube._--This is done by heating the end of the tube and rotating it against an iron rod. The rod must be kept polished and free from rust, and it must not be allowed to become too hot while in use, otherwise the glass will stick to it. _Joining Unlike Glasses._--Joints between unlike glasses are often unstable. When such joints are made it is desirable to blow them as thin as possible, and to avoid the junction of unlike glasses in any complex joint, such as an internal seal. A transitional portion of tubing may be built up by the successive addition and interfusion of beads of one of the glasses to the end of a sealed tube consisting of the other glass. _Joining a Tube to a Very Thin Bulb._--The bulb may be thickened at the point of union by fusing on a bead of glass and expanding this slightly. A small central portion of the expanded part may then be perforated by bursting and the tube joined on. _Insertion of One Bulb Within Another._--A bulb may be divided into two halves by leading a crack round it and the inner bulb is then introduced. The two halves of the outer bulb may be fitted together (care being taken to avoid any damage to the edges), and the bulb may be completed by rotating the contacting edges before the blowpipe until they are soft, and then expanding slightly by means of air-pressure. _Annealing._--For most purposes, in the case of thin, blowpipe-made or lamp-blown glass apparatus, it is sufficient to cool slowly by rotating the finished article over a smoky flame and setting it aside in a place free from draughts, and where the hot glass will not come in contact with anything. Simple bulbs and joints do not even need this smoking; but thick articles, and especially those that are to be subjected to the stress of grinding, need more prolonged annealing in a special oven.