Glass Working Exercises 95 



piece, which is generally required in glass blowing. All such 

 ends may be used up in making the various junctions to be 

 described subsequently, and much glass will be saved by atten- 

 tion to this detail. 



EXERCISE i. To make a wash-bottle jet. 



Take a piece of 4-mm. bore tubing, hold between the thumb and 

 finger-tips of the right hand, and rotate evenly in the hottest portion 

 of the blowpipe flame, until signs of bending appear. Then lightly 

 support with the left hand, until evenly heated, and removing from 

 the flame, gently continue the rotation, but in addition pull the two 

 ends apart slowly, increasing the pull as the glass cools, until the 

 required shape is produced. Wash-bottle jets should not have too 

 pointed a tip, as they are liable to break, and so bits of glass find 

 their way into the beakers and precipitates during washing ; nor 



(2) 



(3) 



FIG. 83. 



should they be too short, or their shape will prevent an even stream 

 being ejected. 



If pulled apart too soon, No. i, Fig. 83, will result, thin walled, 

 weak, and very pointed. If allowed to cool too much before pulling, 

 No. 2 will be produced, from which an even stream will never be 

 ejected. The aim should be in the direction of producing one like 

 No. 3, stout walled, not too stunted, and not pointed enough to risk 

 breakage. 



The jet when made should have both ends heated in the flame 

 until the sharp cut edges fuse, and the ends become rounded, so 

 that they do not cut the rubber tubing forming the junction to the 

 bottle. The jet must be carefully rounded, as the diameter of the 

 orifice will be determined by the amount of heating, and may 

 therefore be arranged to give any desired size of stream. It should 

 be noted here that a common error in jet-making is to suppose that 

 any size of stream may be produced by closing up the tip of the 

 jet, see Fig. 84 (c). While this is to some extent true, it is only so 

 within fairly prescribed limits, as an uneven and jerky stream issues 



