Stained Glass Work: A text-book for students and workers in glass

How to know the Right and Wrong Sides of a Piece of "Antique" Glass.—Take up a sheet of one of these and look at it. You will notice that the two sides look different; one side has certain little depressions as if it had been pricked with a pin, sometimes also some wavy streaks. Turn it round, and, looking at the other side, you still see these things, but blurred, as if seen through water, while the surface itself on this side looks smooth; what inequalities there are being projections rather than depressions. Now the side you first looked at is the side to cut on, and the side to paint on, and it is the side placed inwards when the window is put up.

The reason is this. Glass is made into sheets by being blown into bubbles, just as a child blows soap-bubbles. If you blow a soap-bubble you will see streaks playing about in it, just like the wavy streaks you notice in the glass.

The bubble is blown, opened at the ends, and manipulated with tools while hot, until it is the shape of a drain-pipe; then cut down one side and opened out upon a flattening-stone until the round pipe is a flat sheet; and it is this stone which gives the glass the different texture, the dimpled surface which you notice.

Some glasses are "flashed"; that is to say, a bubble is blown which is mainly composed of white glass; but, before blowing, it is also dipped into another coloured glass—red, perhaps, or blue—and the two are then blown together, so that the red or blue glass spreads out into a thin film closely united to, in fact fused on to, and completely one with, the white glass which forms the base; most "Ruby" glasses are made in this way.

CHAPTER II

Cutting (elementary)—The Diamond—The Wheel—Sharpening—How to Cut—Amount of Force– The Beginner's Mistake—Tapping—Possible and Impossible Cuts—"Grozeing"—Defects of the Wheel—The Actual Nature of a "Cut" in Glass.

No written directions can teach the use of the diamond; it is as sensitive to the hand as the string of a violin, and a good workman feels with a most delicate touch exactly where the cutting edge is, and uses his tool accordingly. Every apprentice counts on spoiling a guinea diamond in the learning, which will take him from one to two years.

Most cutters now use the wheel, of which illustrations are given (figs. 1 and 2).

Figs. 1 and 2.

The wheels themselves are good things, and cut as well as the diamond, in some respects almost better; but many of the handles are very unsatisfactory. From some of them indeed one might suppose, if such a thing were conceivable, that the maker knew nothing of the use of the tool.

For it is held thus (fig. 5), the pressure of the forefinger both guiding the cut and supplying force for it: and they give you an edge to press on (fig. 1) instead of a surface! In some other patterns, indeed, they do give you the desired surface, but the tool is so thin that there is nothing to grip. What ought to be done is to reproduce the shape of the old wooden handle of the diamond proper (figs. 3 and 4).

Figs. 3 and 4.

The foregoing passage must, however, be amplified and modified, but this I will do further on, for you will understand the reasons better if I insert it after what I had written further with regard to the cutting of glass.

How to Sharpen the Wheel Cutter.—The right way to do this is difficult to describe in writing. You must, first of all, grind down the "shoulders" of the tool, through which the pivot of the wheel goes, for they are made so large that the wheel cannot reach the stone (fig. 6), and must be reduced (fig. 7). Then, after first oiling the pivot so that the wheel may run easily, you must hold the tool as shown in fig. 8, and rub it swiftly up and down the stone. The angle at which the wheel should rest on the stone is shown in fig. 9. You will see that the angle at which the wheel meets the stone is a little blunter than the angle of the side of the wheel itself. You do not want to make the tool too sharp, otherwise you will risk breaking down the edge, when the wheel will cease to be truly circular, and when that occurs it is absolutely useless. The same thing will happen if the wheel is checked in its revolution while sharpening, and therefore the pivot must be kept oiled both for cutting and sharpening.

Fig. 5.

It is a curious fact to notice that the tool, be it wheel or diamond, that is too sharp is not, in practice, found to make so good a cut as one that is less sharp; it scratches the glass and throws up a line of splinters.

Figs. 6 and 7.

Fig. 8.

How to Cut Glass.—Hold the cutter as shown in the illustration (fig. 5), a little sloping towards you, but perfectly upright laterally; draw it towards you, hard enough to make it just bite the glass. If it leaves a mark you can hardly see it is a good cut (fig. 10b), but if it scratches a white line, throwing up glass-dust as it goes, either the tool is faulty, or you are pressing too hard, or you are applying the pressure to the wheel unevenly and at an angle to the direction of the cut (fig. 10a). Not that you can make the wheel move sideways in the cut actually; it will keep itself straight as a ploughshare keeps in its furrow, but it will press sideways, and so break down the edges of the furrow, while if you exaggerate this enough it will actually leave the furrow, and, ceasing to cut, will "skid" aside over the glass. As to pressure, all cutters begin by pressing much too hard; the tool having started biting, it should be kept only just biting while drawn along. The cut should be almost noiseless. You think you're not cutting because you don't hear it grate, but hold the glass sideways to the light and you will see the silver line quite continuous.

Having made your cut, take the glass up; hold it as in fig. 11, press downward with the thumbs and upward with the fingers, and the glass will come apart.

Fig. 9.

Fig. 10, a and b

Fig. 11.

But you want to cut shaped pieces as well as straight. You cannot break these directly the cut is made, but, holding the glass as in fig. 12, and pressing it firmly with the left thumb, jerk the tool up by little, sharp jerks of the fingers only, so as to tap along the underside of your cut. You will see a little silver line spring along the cut, showing that the glass is dividing; and when that silver line has sprung from end to end, a gentle pressure will bring the glass apart.

Fig. 12.

This upward jerk must be sharp and swift, but must be calculated so as only just to reach the glass, being checked just at the right point, as one hammers a nail when one does not want to stir the work into which the nail is driven. A pushing stroke, a blow that would go much further if the glass were not there, is no use; and for this reason neither the elbow nor the hand must move; the knuckles are the hinge upon which the stroke revolves.

But you can only cut certain shapes—for instance, you cannot cut a wedge-shaped gap out of a piece of glass (fig. 13); however tenderly you handle it, it will split at point A. The nearest you can go to it is a curve; and the deeper the curve the more difficult it is to get the piece out. In fig. 14 A is an average easy curve, B a difficult one, C impossible, except by "groseing" or "grozeing" as cutters call it; that is, after the cut is made, setting to work to patiently bite the piece out with pliers (fig. 15).

Fig. 15.

Now, further, you must understand that you must not cut round all the sides of a shaped piece of glass at once; indeed, you must only cut one side at a time, and draw your cut right up to the edge of the glass, and break away the whole piece which contains the side you are cutting before you go on to another.

Thus, in fig. 16, suppose the shaded portion to be the shape that you wish to cut out of the piece of glass, A, B, C, D. You must lay your gauge anglewise down upon the piece. Do not try to get the sides parallel to the shapes of your gauge, for that makes it much more difficult; angular pieces break off the easiest.

Fig. 16.

Now, then, cut the most difficult piece first. That marked 1. Perhaps you will not cut it quite true; but, if not, then shift the gauge slightly on to another part of the curve, and very likely it may fit that better and so come true.

Then follow with one of those marked 2 or 3. Probably it would be safest to cut the larger and more difficult piece first, and get both the curved cuts right by your gauge; then you can be quite sure of getting the very easy small bit off quite truly, to fit into its place with both of them. Go on with 4, and then with one of those marked 5 or 6. Probably it would still be best to cut the curved piece first, unless you think that shortening it by cutting off the small corner-piece first will make the curved cut easier by making it shorter.

In any case you must only cut one side at a time, and break it away before you make the cut for another side.

Take care that you do not go back in your cut. You must try and make it quite continuous onwards; for if you go back in the cut, where your tool has already thrown up splinters, it will spoil your tool and spoil your cut also.

Difficult curves, that it is only just possible to get out by groseing, ought never to be resorted to, except for some very sufficient reason. A cartoonist who knows the craft will avoid setting such tasks to the cutter; but, unfortunately, many cartoonists do not know the craft. If people were taught the complete craft as they should be, this book would not have been written.

Here let me say that we cannot possibly within the narrow limits of it go thoroughly into all the very wide range of subjects connected with glass—the chemistry, the permanence, the purity of materials. With the exception of the practice of the craft, probably we shall not be able to go thoroughly into any one of them; but I shall endeavour to mention them all, and to do so sufficiently to indicate the directions in which work and research and experiment may be made, for they are all three much needed in several directions.

It becomes, for instance, now my task, in modifying the passage some pages back as I promised, to go into one of these subjects in the light of inquiries made since the passage in question was written; and I let it for the time being stand just as it was, without the additional information, because it gives a picture of how such things crop up and of the way in which such investigations may be made, and of how useful and pleasant they may be.

Here then let us have—

A LITTLE DISSERTATION UPON CUTTING

Through the agent for the wheel-cutter in England I communicated with the maker and inventor in America, and told him of our difficulties and perplexities over here, and chiefly with regard to two points. First, the awkwardness of the handle, which causes the glaziers here to use the tool bound round with wadding, or enclosed in a bit of india-rubber pipe; and, secondly, the bluntness of the "jaws" which hold the wheel, and which must be ground down (and are in universal practice ground down), before the tool can be sharpened.

His reply called attention to a number of different patterns of handle, the existence of which, I think, is not generally known, in England at any rate, and some of which seem to more or less meet the difficulties we experience, most of them also being made with malleable iron handles, so that fresh cutting-wheels can be inserted in the same handle. His letter also entered into the question of the actual dynamics of "cutting," maintaining, I think rightly, that a "cut" is made by the edge of the wheel (this not being very sharp) forcing the particles of the glass down into the mass of it by pressure.

With regard to the old-fashioned pattern of tool which we chiefly use in this country, the very sufficient explanation is that they continue to make it because we continue to demand it, a circumstance which, as he declares, is a mystery to the inventor himself! Nevertheless, as we do so, and, in spite of the variety of newer tools on the market, still go on grinding down the jaws of our favourite, and wrapping round the handle with cotton-wool, let us try and put this matter straight, and compare our requirements with the advantages offered us.

There are three chief points to be cleared up. (1) The actual nature of a "cut" in glass; (2) the question of sharpening the tool and grinding down of the jaws to do so; and (3) the "mystery" of our preference for a particular tool, although we all confess its awkwardness by the means we take to modify it.

(1) With regard, then, to the nature of a "cut" in glass I am disposed entirely to agree with the theory put forward by the inventor of the wheel, which an examination of the cuts under the microscope, or even a 6 diameter lens, certainly also tends to confirm.

What happens appears to my non-scientific eyes to be this.

Glass is one of the most fissile or "splittable" of all materials; but it is so just in the same way that ice is, and just in the opposite way to that in which slate or talc is.

Slate or talc splits easily into thin layers or laminæ, because it already lies in such layers, and these will come apart when the force is applied between them: but it will only split into the laminæ of which it already is composed, and along the line of the fissures which already exist between them.

Glass, on the contrary (and the same is true of ice, or for that matter of currant-jelly and such like things), appears to be a substance which is the same in all directions, or nearly so, and therefore as liable to split in one direction as in another, and is so loosely held together that, once a splitting force is applied, the crack spreads very rapidly and easily, and therefore smoothly and in straight lines and in even planes.

The diamond, or the wheel-cutter, is such a force. Being pressed on to the surface, it forces down the particles, and these start a series of small vertical splits, sometimes nearly through the whole thickness of the glass, though invisibly so until the glass is separated. And mark, that it is the starting of the splits that is the important thing; there is no object in making them deep, it is only wasted force; they will continue to split of themselves if encouraged in the proper way (see Plates IX. (#x8_x_8_i45) and X. (#x8_x_8_i51)). Try this as follows.