Part 4

The lime-cylinders are sold in air-tight tin canisters holding one dozen each. They are of two qualities--hard and soft. For work where large pictures are required--necessitating the use of the mixed jet with both gases under heavy pressure--the hard limes must invariably be used. But where only a small sheet has to be covered, and one gas only is subjected to the unusual pressure, the soft limes will afford perhaps a better light than the harder ones. Occasionally the lime, be it hard or soft, will split. In such a case it ought to be immediately replaced by a fresh one, otherwise the flame may possibly be diverted towards the condensing lenses, and will fracture that nearest to the light. It is advisable always to keep a spare lime within the lantern, lying on the tray to which the jet is attached. By this means it gets warmed, and ready for use if required. Lime is most absorbent of moisture, and will, if kept where air can get to it, swell to double its former size, and finally crumble to powder. For this reason the tin canister containing the cylinders should have stretched over it, when once opened, a broad indiarubber band which will cover the junction between lid and box. If this precaution be neglected, the limes will swell with a force sufficient to break the tin-containing vessel asunder. A compressed lime cartridge, to which water is applied by artificial means, has lately been successfully introduced to supersede explosives hitherto used for mining purposes. This will show the immense power of expansion of which the substance is capable.

THE SCREEN OR SHEET.

And now a word about the best form of screen or sheet for showing lantern pictures upon. The best possible form of surface is a smooth whitewashed wall; but as this is not commonly found among the appointments of a sitting-room, where the lantern will be wanted, we must find some substitute which will most nearly resemble it. A sheet of cartoon paper, which can be bought of any length, and measuring more than four feet across, will do well if only a small disc is desired. The paper can be rolled up out of the way at a minute’s notice. If a larger screen is wanted, it can be made of stout calico, faced with white paper, and can be made to roll up and down like a school map of large dimensions. A map-mounter, or even an upholsterer, would soon rig up such an arrangement.

There is a very effective way of showing small pictures and diagrams with an oil-lantern, which I have more than once adopted, where a room has been long in proportion to its breadth. This is to make a wooden frame just large enough to take the full width of a sheet of tracing-paper, and to put this screen between the lantern and the spectators. Tracing-cloth should be avoided, as it is so transparent that the light streaming from the lens makes a blotch in each picture when seen through it.

If the lantern is brought into regular use--in a schoolroom, for instance--it might be thought worth while to have a canvas sheet whitewashed, and hung in the same manner that a stage drop-scene is fixed. In making such a screen, the canvas should be tacked on a frame, and should have a coating of thin glue, which should be allowed to dry before two or more coats of whitewash are applied. It will be understood that a really opaque screen, such as this represents, is the more effective, because the light, instead of being partly lost--as it must be in penetrating an ordinary calico sheet--is reflected and utilized.

But for public exhibitions on a large scale, the calico sheet is the screen commonly in vogue, for it is conveniently put up and taken down, and can be rolled into a bundle for easy transport. A sheet properly hung should be as flat as a board and perfectly free from wrinkles of any kind, and this can be accomplished without much difficulty by adopting the following method, which is applicable to screens from twelve feet square upwards.

Showing method of hanging a sheet.]

The sheet should have at its top edge a strong cord sewn into its hem, which cord should terminate at each side with a loop. On its sides and bottom edges, the sheet should have brass curtain rings sewn on to it at intervals of two feet. Having chosen the position of the screen, a couple of screw-eyes are screwed into the roof, or cornice near the top of the hall, at such a distance apart that the sheet can easily go between them. Through each of these screw-eyes is passed a thin, strong line, having at its end a clip like that commonly attached to a dog’s chain. This clip is to clutch the loop of rope on each side of the sheet. The sheet can now be pulled up into position: the free ends of the cord being fastened to screw-eyes in the floor. It now merely remains to lace with string the curtain rings on the side of the sheet to the adjacent cord, and the arrangement is complete. The annexed diagram shows the upper corner of such a sheet, with its attachments, as just explained. Where the hall is of such a height that this plan is not available, or where the stern custodians faint with horror at the thought of their walls or ceilings being pierced with a screw-hole, the same method can be carried out by fastening the screw-eye to a timber upright on each side, supported by light struts.

Some persons prefer a sheet stretched on a frame, and such a frame of a very portable character can be easily devised. The frame itself is best made of lengths of pine, about the size of broom-handles. These can be joined together so as to make a frame of any reasonable dimensions, by six-inch lengths of brass tubing. The same tubing, mitred into L-pieces, will serve for the four corners. The sheet is furnished with tapes to secure it to the frame, and the woodwork is kept in an upright position by strong cords fastened by screw-eyes to the floor. The appearance of such a screen is much enhanced if the plain woodwork be hidden by a little drapery in the shape of narrow curtains at each side, and festoons of the same material above.

PICTURES FOR THE LANTERN.

Before the advent of the art of photography, pictures or slides for the lantern were traced on glass and painted by hand; and this art was carried to very great perfection. But no handiwork can equal the productions of the photographic camera; so that when it was found possible to produce transparent positives on glass, that could be magnified on the sheet to any extent without deterioration, the occupation of the artist on glass was almost gone. Photographs are now almost exclusively used, and form, when properly executed, the finest pictures for lantern use. The manner of their production is fully described in my little book ‘How to Photograph;’ but as there may be many would-be lanternists who do not care to dabble in photography, I will here give a few plain directions by which lantern slides can be extemporised.

The standard size for lantern pictures is 3¼ × 3¼ inches. The glass chosen should be as thin as possible, and quite free from scratches, bubbles, or flaws of any kind whatever. Remember that a piece of the finest hair which may well be overlooked upon the slide itself, will appear on the screen as a huge snake. In like manner a tiny bubble in the glass is magnified into a blemish the size of a soup-plate. Glass presents a very difficult surface to draw or paint upon, particularly if water-colours are employed, but by coating it with a transparent medium in the first instance the difficulty is much reduced. A film of plain collodion will, when dry, give a surface that can be easily sketched upon with a fine pen and Indian ink. The sketch so made can afterwards be filled in with water-colour, tempered with prepared ox-gall, and taking care that the colours used are those which are naturally transparent. Prussian blue, indigo, lake, the madders, gamboge, burnt and raw Sienna, Vandyke brown, are all transparent pigments, and will answer every purpose. Mixed with one another in the manner detailed in any manual of water-colour painting, greens, purples, and all secondary and tertiary tints are readily obtainable.

Another method, and an easier one, for producing lantern slides was introduced some years ago by the Rev. W. H. Dallinger; and although the author of the method intended it for drawings of microscopic subjects only, and with that idea brought it before the notice of the Royal Microscopical Society, it will be readily seen that it is adapted to all manner of lantern pictures. This method is best described in its inventor’s own words: ‘On finely ground glass drawing with a black-lead pencil is as easy as drawing upon cardboard. I get squares of glass to suit the size of my lantern carefully ground on one side like the focusing-glass of a camera.’ The author goes on to describe how, by sketching upon the finely ground surface with a well-pointed hard pencil--HH or HHH--and shading with a softer one, such as HB, capital effects can be obtained. ‘If it be necessary to put in colour it may be done, cleanly and carefully over the shading; thus one layer of colour suffices. Now, of course, although we have a perfect drawing of the object, with all the detail accurately given, it is not a transparency. But we can easily make it one. Thin some good pale Canada balsam with benzine to about the consistency of cream, and simply float it over the ground surface of your glass; pour off until the drop comes very sluggishly. Then reverse the glass so that the corner from which the balsam was flowing off be placed upwards. Let the return flow reach about the middle; then reverse it again, and move it in several directions to get the balsam level. This may be done with a very little practice, so that the surface shall be undistinguishable from glass. We have now a perfect transparency. All that is required is twenty-four hours for hardening (keeping the glass level), and then another square of glass fastened on to it by strips of paper at the edges, with small pieces of card at the corners to prevent contact, and it makes an admirable lantern transparency.’

A hint about giving a fine grain to glass will not be out of place. Upon a perfectly flat and firm table lay a piece of glass say six and a half inches square, for this size can afterwards be cut across into four lantern pictures. A sheet of wet blotting-paper under the glass will keep it steady. Now pour upon its surface a mixture of flour-emery and water. Place another piece of glass above, and work it round with a circular motion, constantly spooning up the mud formed by the emery and water, and which oozes out between the glasses, and replacing it between them. In a short time both glasses will be beautifully ground on the surfaces which have been rubbed together. A moment’s consideration will show that the ground effect is produced by the surface being broken up into innumerable tiny pits, each one of which scatters the light. By Mr. Dallinger’s method of filling up these pits with a glassy medium like Canada balsam, the glass is once more presented with a flat surface, and therefore becomes once more transparent.

By whatever means the picture is produced the operator should have a glass transparent easel to work upon placed at an angle of forty-five degrees, with a sheet of paper underneath it to throw the light up through the glass he is drawing upon. A good easel can be made of a small frame--that belonging to a twopenny slate will do--attached to a base-board, and supported on each side by struts. A ledge of wood screwed across the frame makes a convenient support for the picture. The annexed cut will sufficiently explain the arrangements described.

Glass easel.]

And now a word or two about mounting the picture. As Mr. Dallinger points out, a cover-glass should be provided, but it should be prevented from actually touching the painted surface. This is best brought about by using the masks cut out of black paper, and sold for the purpose. A mask is inserted between the glasses, after which the whole is fastened together by pasting a slip of paper round the edges of the double glass, and turning it over on either side. Gum arabic with twenty-five per cent. loaf-sugar added, is a good medium by which to attach paper to glass.

ON THE COLOURING OF PHOTOGRAPHIC TRANSPARENCIES.

There are many amateur photographers nowadays who can produce fair transparencies for the lantern, but at the same time there are many possessors of a lantern who know nothing about the ‘black art.’ Luckily for these, first-class pictures can be bought cheaply, their average price ranging from eighteenpence to two shillings each. Any optician’s catalogue will show what an immense variety of subjects there is to chose from; not only can we obtain landscapes of nearly every part of the world, but we can purchase figure studies, copies of various pictures from books, maps, diagrams of scientific matters--micro-photographs and statuary. These slides if coloured are double the price of plain ones, and if very well coloured their price is quadrupled.

It would therefore be serviceable to many if they could learn how to colour such pictures for their own use, and I give simple directions how this can be accomplished. At the same time it is only fair to state that the work is really difficult, and anyone to attain even slight proficiency in slide-painting must devote a great deal of time and patience to the subject.

The photographic slide as sold consists of two glasses, one of which bears the photograph. This is separated from the cover-glass by a paper mask, the whole being bound round by a fillet of gummed paper. After carefully cutting round this fillet the two glasses may be separated, and the one bearing the picture is placed, varnished side upwards, upon the glass easel, ready for colouring. Some colourists speak in favour of water-colours for glass-painting, others prefer oil-colours, while some, I understand, employ both on the same picture. I have tried each system, and most certainly recommend oil-colours as being both easier to work with, and doing more satisfactory work into the bargain than water-colours.

The materials required comprise ordinary oil-colours in tubes, of which the following are perhaps the most useful that can be employed for the purpose:

Italian Pink. Raw Sienna. Yellow Lake. Chinese Orange. Brown Pink. Prussian Blue. Indigo. Neutral Tint. McGilp. Brown Madder. Rose Madder. Purple Madder. Crimson Lake. Burnt Sienna. Ivory Black.

It is curious to observe that the suitability of these colours for the particular purpose of glass-painting varies with the method of manufacture. I find by experience that one maker’s Prussian blue is better than another’s, while for a suitable crimson lake I have to go to quite a different shop, and so on.

The brushes used must be of the best, the majority of them being camel-hair, a few fine sables being kept for special touches. It is also necessary to provide some good large bushy camel-hair brushes to be used as softeners.

A flat porcelain palette is better than one of any other material, for the strength of the tints is seen well, and the surface can easily be cleaned with a little turpentine. A flexible palette knife must also be provided.

Dabbers to soften down skies and other flat masses of colour can be made by wrapping a ball of cotton wool in fine wash-leather. The leather should be first thoroughly washed with soap and water, and it will be better if a little of the soap be left in it as it dries, for this renders it soft and pliant. Both dabbers and brushes should be kept in a dust-tight box, for dust is the greatest enemy of the slide-painter.

It will be noticed that the list of colours given includes those only which are transparent, many others used in ordinary oil-painting being omitted. It is obvious that opaque colours like Naples yellow or chrome yellow would simply appear black on the sheet. The tyro who is used to other methods of painting, and has some idea of the harmony of colours, will, of course, have an immense advantage over anyone without artistic knowledge or feeling; and when he has once mastered the technicalities of the new work, will soon be able to produce passable pictures. The list of colours given is necessarily limited for the reason already given, but their number can be increased indefinitely by judicious blending one with the other. Let me give a few instances.