Part 1 (1/2)

A Handbook of Laboratory Glass-Blowing

by Bernard D Bolas

PREFACE

To cover the whole field of glass-blowing in a small handbook would be impossible To atte commercial apparatus would involvethe essential details of manipulation that a novice needs I have, therefore, confined myself as far as possible to such work as will find practical application in the laboratory and will, I hope, prove of value to those whose interests lie therein

Thehave been chosen solely with the view to economy of space without the undue sacrifice of clearness

BERNARD D BOLAS

Handbook of Laboratory Glass-Blowing

CHAPTER I

Introduction and Preliminary Re--Choice of Apparatus--Tools and Appliances--Glass

Glass-blowing is neither very easy nor very difficult; there are operations so easy that the youngest laboratory boy should be able to repeat the been shown the way, there are operations so difficult that years are needed to train eye and hand and judgreater number of scientific needs lie between these two extree nulass tube or make a T piece that will not crack spontaneously, and the fault is rather one of understanding than of lack of ability to carry out the necessarythe scheme of instruction adopted in this handbook, it will be well for the student to pay particular attention to the reason given for each detail of the desirable procedure, and, as far asreason, he can evolve scheh, as a rule, those given in the following pages will be found to embody the result of many years' experience

There is a wide choice of apparatus, from a simple mouth-blowpipe and a candle fla device

All are useful, and all have their special applications, but, for the present, ill consider the ordinary types of bellows and blowpipes, such as one usually finds in a chemical or physical laboratory

The usual, or Herepath, type of gas blowpipe consists of an outer tube through which coal gas can be passed and an inner tube through which a stream of air

1 It is desirable to have the three centring screws as shown, in order to adjust the position of the air jet and obtain a well-shaped fla 1, _a_ and _b_ show the effects of defective centring of the air jet, _c_ shows the effect of dirt or roughness in the inside of the air jet, _d_ shows a satisfactory fla 1]

For e to have what is soe” blowpipe; that is one in which jets of varying sizethe work for more than a fraction of a second Such a device is made by Messrs Letcher, and is shown by _e_, and in section by _f_ Fig 1 It is only necessary to rotate the desired jet into position in order to connect it with both gas and air supplies A sas and air may be made by a partial rotation of the cylinder which carries the jets

For specially heavy work, where it is needed to heat a large lass, a multiple blowpipe jet of the pattern invented by estion derived froas furnace, is of considerable value This jet consists of a block ofcentral and the other six arranged in a close circle around the central hole To each of these holes is a coas supply, and an air jet is arranged centrally in each Each hole has also an extension tube fitted into it, the whole effect being that of seven blowpipes In order to provide a final adjust seven holes which correspond in size and position to the outer tubes is arranged to slide on parallel guides in front of these outer tubes

[Illustration: Fig 2]

The next piece of apparatus for consideration is the bellows, of which there are three or h all consist of two essential parts, the blower or bellows proper and the wind cha 2; _a_, is the form which is commonly used by jewellers andsmall furnaces Such a bellows may be obtained at almost any jewellers' supply dealer in Clerkenwell, but it not infrequently happens that the spring in the wind cha, and hence the air supply tends to vary in pressure

This can be i, but an easier way and one that usually gives fairly satisfactory results, is to place an ordinary screw-clip on the rubber tube leading frohten this until an even blast is obtained

Another form of bellows, made by Messrs Fletcher and Co, and common in most laboratories, is shown by _b_; the wind chamber consists of a disc of india-rubber clamped under a circular fra 2, _b_

The third form, and one which my own experience has caused me to prefer to any other, is cylindrical, and stands inside the pedestal of the blowpipe-table A blowpipe-table of this description is made by Enfer of Paris