A HANDBOOK OF LABORATORY GLASS-BLOWING

To my Friends
Eric Reid
and
Sidney Wilkinson

A Handbook of Laboratory Glass-Blowing

BY

BERNARD D. BOLAS

WITH NUMEROUS DIAGRAMS IN THE TEXT

BY NAOMI BOLAS

LONDON
GEORGE ROUTLEDGE & SONS, LTD
New York: E. P. DUTTON & CO.
1921

CONTENTS

CHAP. PAGE
I. Introduction and Preliminary Remarks—General Principles to be observed in Glass Working—Choice of Apparatus—Tools and Appliances—Glass 1

II. Easy Examples of Laboratory Glass-Blowing—Cutting and Sealing Tubes, Tubes for High Temperature Experiments—Thermometer-Bulbs, Bulbs of Special Glass, Pipettes, Absorption-Bulbs or Washing Bulbs—Joining Tubes, Branches, Exhaustion-Branches, Branches of Dissimilar Glass, Blowing Bulbs, A Thistle Funnel, Cracking and Breaking Glass, Leading and Direction of Cracks—Use of Glass Rod or Strips of Window-Glass, Joining Rod, Feet and Supports—Gripping Devices for use in Corrosive Solutions—The Building up of Special Forms from Solid Glass 10

III. Internal Seals, Air-Traps, Spray Arresters, Filter-Pumps—Sprays, Condensers; plain, double surface, and spherical—Soxhlet Tubes and Fat Extraction Apparatus—Vacuum Tubes, Electrode Work, Enclosed Thermometers, Alarm Thermometers ... Recording Thermometers, "Spinning" Glass 32

IV. Glass, its Composition and Characteristics—Annealing—Drilling, Grinding, and Shaping Glass by methods other than Fusion—Stopcocks—Marking Glass—Calibration and Graduation of Apparatus—Thermometers—Exhaustion of Apparatus—Joining Glass and Metal—Silvering Glass 55

V. Extemporised Glass-Blowing Apparatus—The use of Oil or other Fuels—Making Small Rods and Tubes from Glass Scraps—The Examination of Manufactured Apparatus with a view to Discovering the Methods used in Manufacture—Summary of Conditions necessary for Successful Glass-Blowing 80

Index 105

PREFACE

To cover the whole field of glass-blowing in a small handbook would be impossible. To attempt even a complete outline of the methods used in making commercial apparatus would involve more than could be undertaken without omitting the 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.

The method of treatment and somewhat disjointed style of writing have 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

Glass-blowing is neither very easy nor very difficult; there are operations so easy that the youngest laboratory boy should be able to repeat them successfully after once having been shown the way, there are operations so difficult that years are needed to train eye and hand and judgment to carry them out; but the greater number of scientific needs lie between these two extremes. Yet a surprisingly large number of scientific workers fail even to join a glass 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 necessary manipulation.

In following the 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 as may be, to memorise it. Once having mastered the underlying reason, he can evolve schemes of manipulation to suit his own particular needs, although, 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 flame to a power-driven blower and a multiple-jet heating device. All are useful, and all have their special applications, but, for the present, we will 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 may be blown. Such a blowpipe is shown in section by Fig. 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 flame, but these screws are sometimes omitted. Fig. 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 flame.

Fig 1

For many purposes, it is an advantage to have what is sometimes known as a "quick-change" blowpipe; that is one in which jets of varying size may be brought into position without stopping the 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 small bye-pass ignites the gas, and adjustment of gas 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 mass of glass, a multiple blowpipe jet of the pattern invented by my father, Thomas Bolas, as the result of a suggestion derived from a study of the jet used in Griffin's gas furnace, is of