It is provided with a single gas socket, into which either a large or small gas tube may be screwed. The larger tube is 5.5 inches long and 0.75 of an inch in diameter. The smaller tube is the same length, and half an inch in diameter. The axis of the larger tube is 3.5 inches above the table at the point of support, and is inclined to the horizontal at an angle of 12°. The axis of the smaller tube is 2.5 inches above the surface of the table, and is inclined to the horizontal at the same angle as the larger one.
The air jets are simply pieces of glass tube held in position by corks. The gas supply is regulated by a well-bored tap. The air supply is regulated by treading the bellows — no tap is requisite. The bellows employed are ordinary smiths' bellows, measuring 22 inches long by 13 inches wide in the widest part. They are weighted by lead weights, weighing 26 lbs. The treadle is connected to the bellows by a small steel chain, for the length requires to be invariable. As the treadle only acts in forcing air from the lower into the upper chamber of the bellows, a weight of 13 lbs. is hung on to the lower cover, so as to open the bellows automatically.
The air jets which have hitherto been found convenient are:
for the small gas tube
- a tube 0.12 inch diameter drawn down to a jet of 0.032 inch diameter for small work;
- plain tubes not drawn down of 0.14 inch, 0.127 inch, and –0.245 inch diameter, and for the large gas tube, plain tubes up to 0.3 inch in diameter.
The table is placed in such a position that the operator sits with his back to a window and has the black calico screen in front of him and to his right. The object of the screen is to protect the workman against draughts. The table is purposely left unscreened to the left of the workman, so that long tubes may be treated.
§ 17. Other appliances which will be required for GLASS-BLOWING are of the simplest character.
(1) Small corks for closing the ends of tubes.
(2) Soft wax — a mixture of bees' wax and resin softened by linseed oil to the proper consistency, easily found by trial, also used for temporarily closing tubes.
(3) A bottle of vaseline for lubricating.