Home › Contents › Preparing Slides for the Lantern

Preparing Slides for the Lantern

Those of my readers who wish to produce their own photographs for projection by the lantern can do so by studying the next chapter, which is devoted to photography. With perseverance they will be able to bring home photographic mementoes of their walks abroad, and transfer them to glass for use in the lantern. By this means they can show their friends large pictures of the places which they have visited, and so add to the pleasures of their wanderings by reproducing the objects seen again and again. Such transparencies can be easily taken from a negative picture by gas light. A sensitive dry plate is placed with the negative in a printing frame, and exposed to gas light for two or three seconds; it is then developed and finished in the way described for a negative. When dry, it must be mounted in the following manner, first taking care that the glass is cut to the proper size for the lantern. The standard size is 3 1/4 inches square. Procure some thick black paper, and cut it into a mask of one of the shapes shown. Having dusted the photograph, lay the mask upon it, and above it place a cover glass of the same size. With thin black paper, cut into strips half an inch broad, and brushed over with fresh starch paste; now bind the two glasses together by their edges, and the slide is finished.

Those who do not wish to dabble in the mysteries of photography must be content with far inferior results. Still there are two methods of preparing slides which are open to them by which fair effects can be obtained. Sheets of coloured designs made expressly for lantern slides can be purchased at most artists' colour dealers. These are printed in transparent tints, and can be transferred bodily to glass, the paper peeling off and leaving nothing but the coloured design behind it. Each picture is first brushed over with a preparation sold for the purpose and supplied with the sheet of designs. It is then left to dry for a day or two, then soaked in water, and pressed on to the glass. The back of the paper is now carefully rubbed and sponged, when it will with a little help come away from the glass. A wash in water, and a coat of varnish complete the operation. The designs are principally illustrations to fairy tales and like subjects suitable for juvenile audiences, and are effective as far as they go.

Those, however, who are possessed of any artistic skill will hardly be content with mere printed designs, but will wish to try to produce something of a more original nature. The surface of glass is so smooth that it is very difficult to draw a line upon it even with a finely pointed brush, and it requires a great deal of practice before a passable picture can be produced. But a method of obviating this difficulty has been found, and was, I believe, first adopted by the Rev. W. H. Dallinger. At any rate, this gentleman brought before the Royal Microscopical Society a paper upon the subject, which explains his method of working. From this paper I quote the following remarks:-- "Most working microscopists have felt the necessity, in reading papers on their work, of accurate illustration. Mere enlarged drawings fail in matter of detail, unless extravagant labour is expended and considerable time employed. Even then the light of an ordinary lecture hall is not enough to enable the most distant of the audience to clearly see them. It is only by means of the lime light and transparencies that really useful illustrations can be given. But here the difficulty is to prepare them accurately and inexpensively. Photography cannot be employed in all cases; and even where it can be, it involves more labour than most microscopists can afford. Drawing and painting on glass in the usual method is an art that it takes years thoroughly to learn; and to employ one who has learnt it to draw from nature a highly magnified object would be to introduce innumerable errors of interpretation, unless our artist be a microscopist himself. I obviate all these difficulties by the following method. "On finely ground glass drawing with a blacklead 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 focussing glass of a camera. Now, with the ground side up, the camera lucida may be used with this as well as with drawing board if a piece of white paper be placed beneath it, and the object drawn in the usual way; for outlining and delicate shading, I employ HHHH and HHH pencils; for deep shadows, I use HB. By a very delicate employment of the pencil, shadows softer than can be secured by lithography may be made. The camera lucida, of course, is not necessary; we may draw with the eye and hand alone. 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 stripes of paper at the edges, with small pieces of card at the corners to prevent contact, and it makes an admirable lantern transparency." Although, as will at once be seen, this method of preparing slides is intended for the reproduction of microscopic objects, it can be well made applicable to the more ordinary purposes of the lantern. I need hardly mention that only transparent colours must be used, but as such colours form the major part of an ordinary box of water colours, there will be no difficulty here. Gamboge, Prussian blue, lake, burnt and raw sienna, Vandyke brown, are all naturally transparent, and from them an unending variety of compound tints can be obtained. Flake white, which I may quote as an example of an opaque pigment, would appear black upon the screen.

The outline of the picture can be traced from any book by placing the ground glass just above it, and going over the lines with a hard pencil. This outline can afterwards be strengthened with Indian ink by means of a fine pen. Some of the best subjects can be chosen from those extremely comic caricatures of German origin which are published in sheets. The figures may be painted in bright colours, and the background either tinted or blocked out with black paint. The latter plan gives the design a very brilliant appearance upon the disc. In any case the slides should be mounted with a mask and protecting glass as already indicated.

ALTHOUGH the art of taking pictures by the aid of the sun has only been discovered for little more than forty years, it has made such rapid strides that many thousand people are dependent upon it for their daily bread. It gives employment not only to those who call themselves photographers, but to an immense number of persons who contribute to the photographer's requirements. Paper-makers, glass-makers, manufacturers of special chemicals required in the art, cabinet-makers, and hosts of others, may indeed thank the sun for his daily gift of light twice over, for they are indebted to him even more than others.

The standard photographic process up to very recent times is known as the wet collodion method. In this process, a glass plate is covered with a thin layer of collodion (made by dissolving gun-cotton in ether and alcohol). It is then placed in a bath of nitrate of silver. The silver combines with certain iodides and bromides contained in the collodion, forming an intensely sensitive film on the surface of the glass. This glass is now shut up in a slide, the slide is placed in the camera, a shutter is removed so as to expose the sensitive surface of the glass to the action of light, and the picture is taken. It is then developed and fixed, and forms what is called a negative, from which any number of positive prints on paper can be procured. Such is briefly an outline of the process in vogue until lately. It is sure and certain, as may be judged from the fact that it has for many years been practised by all professional photographers. There are many excellent handbooks published, giving details which will enable any one of ordinary intelligence to succeed in taking pictures by the wet collodion method, and I would strongly advise those commencing to practise the art to avail themselves of that way of gleaning information concerning it. The time thus spent in learning necessary manipulations connected with cleaning the glass, adjusting the apparatus, and compounding the chemicals--which cannot here be entered into--will be found most useful, if not indispensable to the would-be photographer.

There are many who prophesy that the wet collodion process must be considered a thing of the past; whether or not this sweeping assertion is correct, there is no doubt that the old process has in a great measure been relinquished in favour of one entirely new. This recent development of photography is known as the gelatino-bromide process, and as little is published concerning it, I think it advisable to give full details of it, instead of reiterating instructions for working the older method, which, as already stated, can be found in other books.

In the gelatino-bromide process the sensitive silver salt is mixed with an emulsion of gelatine and spread on a glass plate. The plate is afterwards dried, and in this state will keep indefinitely, so long as it is jealously guarded from light and damp. In the older process the plate had to be exposed in the camera directly it was sensitised, so that a photographer was obliged to be accompanied by a tent and a whole laboratory of chemicals if he wanted to take a picture away from home. In the new method the necessary impediments can be carried in one hand, and a tourist can pack enough apparatus and materials to take fifty views without any great addition to his luggage. The process is, moreover, so extremely rapid that moving objects can be easily secured.

The first operation is to make the sensitive emulsion which is afterwards applied to the glass plates. And the formula which I recommend is that adapted by Messrs. Wratten and Wainwright, of Great Queen Street, London, pictures on whose plates gained four prize medals, and other honours, at the last exhibition of the Photographic Society of Great Britain. The instructions which they give are as follows:-- To make five ounces of Gelatino-bromide Emulsion.

Formula.

Gelatine (Nelson's No. 1) 90 grains. Ammonium bromide 45 grains. Silver nitrate 75 grains. Water (distilled) 5 ounces.

Select a twenty-ounce bottle with a securely fitting stopper. First pour in four ounces of the water, dissolve therein the bromide of ammonium, then add the gelatine, and leave the mixture to soak for one hour. The advantage of a well-fitting stopper will be obvious; for if, in shaking up, any of the liquid were lost, some of the bromide salt would go therewith, and the balance would be disturbed. There is a manifest advantage in first dissolving the bromide salt in the water, for we thus succeed in evenly and equally distributing it throughout the whole body of the gelatine; and if precaution be taken in regard to the stopper of the bottle, there need be no loss of bromide. Next dissolve in a separate bottle seventy-five grains of nitrate of silver in the remaining ounce of water. Place the two bottles in a jar or jug of water of 100 degree temperature, and solution of the gelatine will quickly take place. Now carefully unite (in the dark room, of course) the contents of the two bottles. The nitrate of silver solution may be slowly stirred into the bromised gelatine, or it may be added in small quantities with a thorough shaking between each. Either method, if well done, is efficient. We have now a gelatino-bromide emulsion containing a slight excess of bromide, and this slight excess, while not in any marked degree detracting from its sensitiveness, will be found of eminent service when we arrive at the developing stage. By the addition of the nitrate of silver to the bromised gelatine, an action termed "double decomposition" is originated; in other words, an interchange of elements takes place between the two salts. If nitrate of silver were added to water containing bromide of ammonium in solution, an interchange of elements would instantly take place; insoluble bromide of silver would subside, and nitrate of ammonium would remain in solution. But gelatine, being a viscid medium, retards this chemical interchange, and therefore time must be given to bring it completely about. In order, therefore, to keep the gelatine in a liquid condition, we place the bottle in water of 100 degree temperature, and it is found in practice that a period of from four to six hours will complete the double decomposition. If water of a higher temperature than 100 degree be employed, the interchange will be completed in a shorter space of time, as the gelatine, being thereby rendered more limpid, presents less obstacle. But we must bear in mind that 100 is a safe temperature, and that a greater heat can only be employed at the risk of decomposing the gelatine, the results of which would be inconvenient at the final stage of development, these results being blisters and frilling. The necessary heat can conveniently be obtained from a gas-jet. This jet can be placed underneath a large tin saucepan containing the bottle of emulsion placed in water. The height of the flame, and its distance from the bottom of the saucepan to ensure the correct heat, can easily be determined previously by the aid of a thermometer. The greatest care must be taken against the accidental admission of any white light, which would infallibly spoil the entire operation by rendering the emulsion useless.

A period of six hours having been given for this digestion, take out the bottle of emulsion, and pour it into a flat dish to set, and when so set, the final operation may be performed.

It will be seen from the foregoing remarks that the gelatine holds in suspension two compounds, namely, bromide of silver, and nitrate of ammonium. The former is the sensitive salt, the latter is matter in the wrong place, and must be removed, or it will crystallise on the plates and spoil them. In order to remove the nitrate salt in the most effective manner, the following method is all that can be desired.

For this some simple apparatus will be required. First, a bag of that napless canvas which ladies employ as the basis for Berlin wool work. Second, a trough (see sketch), twelve inches by ten, or less, about ten inches deep, and fitted with a tap to draw off the water. It has a ledge round the inside, about two inches from the top, on which rests a tray. This tray has wooden sides, and a calico bottom. It is shown at the upper part of the drawing. Scrape the gelatine up from the dish with a strip of glass, and transfer it to the canvas bag; close the aperture of the bag, and by the pressure of the thumb and fingers force the gelatine through the meshes of the canvas into a basin of water. We now have gelatine in extremely fine division; but it is also mixed with a vast excess of water. Now we pour the whole on to the tray with the calico bottom, and the water will pass off, leaving the gelatine high and dry. In order that we may be sure that the proper amount of washing is done, it is as well to fill up the trough with a fresh supply of water, and let the tray float upon it for ten minutes.

When the water has been finally drained off, we transfer the gelatine to a bottle, stand it in hot water, and when dissolved and filtered, it is ready for coating the plates. This last operation is by no means an easy one, and is also impossible for those who have not a room devoted to the purpose which can be kept in darkness and free from dust. Many will therefore prefer to obtain their plates ready for use from the manufacturers--but for those who wish to produce their photographs from first to last by their own work, I append directions.

The light by which all the foregoing operations are conducted must be of a strictly non-actinic quality. Yellow glass such as is used to protect the plates in the old collodion process is useless here. The light must be of a deep orange colour. Messrs. Wratten and Wainwright sell a special form of paper prepared for the purpose, which is far cheaper and better than any glass which can be obtained. With a window or lantern furnished with this medium, the plates can be prepared without apprehension of their being fogged. It is as well to have in the coating-room a dry cupboard in which the plates can be placed soon after being coated; but failing this, shelves, carefully dusted previous to use, can be used for the purpose.

Firstly the warm emulsion must be filtered, or the coated plates will be covered with little specks and other blemishes, which will render them quite unfit for artistic purposes. This is best done by twisting a piece of writing paper into a funnel (see cut), and pushing a little plug of cotton wool half through the orifice at its lower part. This will fit comfortably into a wide-mouthed phial, and, if the emulsion be carefully poured into it, will rapidly run through, and the wool will withhold any floating particles. In very cold weather the glass plates, previously carefully cleaned, should be heated by being placed upon a flat tin box, or other receptacle, half full of boiling water, but in warm weather this is not necessary. Taking a plate upon a pneumatic holder, it is held horizontally in the left hand, while the right hand, holding the emulsion bottle, is carefully brought above It. A little pool of the gelatine is poured on to the centre of the glass, and is carefully guided all over it with the help of a glass rod. The excess of gelatine is then drained into the filter--which should now be placed in a clean phial standing near. On no account should the excess be poured back into the coating bottle, or spots will inevitably result.

The first plate, being coated, is placed upon a slab of marble or plate-glass, which has previously been accurately levelled by means of a spirit-level. The second plate can then be dealt with, and so on with the next five or six, the glass guiding-rod being placed in a jug of hot water when not in use. When the levelled slab is covered with plates (it should be large enough to hold about ten), the first two or three will be found to be set, when they can be removed to the shelf or drying cupboard to make room for more. When the coating bottle is exhausted--that which has been placed aside for the excess from the plates can now be used, but it will probably require heating in warm water first. When the plates are dry (an operation which will take from six to twenty-four hours according to the state of the weather), they are ready for the camera. These plates require but half the exposure usually given to a wet collodion plate. In bright weather a landscape can be easily taken in three seconds, but quality of light and subject vary so much that no precise directions can be given. The matter must be decided altogether by experience. Messrs. Wratten and Wainwright thus deal with this portion of the subject:-- "The time of exposure may in the first instance be readily ascertained by the following method. Place the camera in position, focus the picture, and insert the slide. Cap the lens, and draw out the shutter, so as to expose one quarter of the plate. Give this five seconds, and in like manner give three other exposures on the same plate of five seconds each. Develop them, as though only one exposure had been given, and when finished, one of the four exposures will generally be right, and the time may be easily computed." The development can be conducted either by the alkaline method or by the ferrous-oxalate process. The former method gives greater latitude in exposure, as under or over exposure can in a measure be remedied during development. The latter is far easier and more cleanly; indeed, the modern photographer need never be known by the blackness of his fingers, as in the old days of the art. Supposing that we are about to develop a quarter plate (4 1/4 X 3 1/4) by the alkaline method, we shall require one stock solution compounded thus:-- Ammonia liquor, fort 1 ounce. Bromide of potassium 60 grains. Water 2 ounces. Place the exposed plate in an ebonite dish or porcelain tray a little larger than itself, covered with water. While it is soaking, fill a two-ounce measure with water, and add to it as much pyrogallic acid as will cover the tip of the blade of a penknife (about two grains). This will immediately dissolve, and should have added to it five drops of the ammonia solution. Now pour off the water from the plate, pour on the developer instead, and watch the result. The high lights of the picture will soon appear, and will gradually acquire force. As soon as the details are pretty generally visible, drop eight or ten minims more of the ammonia solution into the developing cup, pour the contents of the tray into it, and immediately return to the plate. The picture will now rapidly gain vigour, but will most likely require a few more drops of ammonia solution applied as just directed. It must now be thoroughly washed under a tap, and then placed in the fixing bath.

Hyposulphate of soda 2 ounces. Water Half a pint.

This bath will gradually clear the picture, and the glass should not be removed from it until it appears uniformly so. It must now be washed most thoroughly and left in a dish of water for at least half an hour. It is then rinsed once more under the tap, and can be put in a rack to dry. A coat of varnish completes the negative.

A most convenient modification of the ferrous-oxalate developer has lately been brought under my notice by M. Wernerke, who has invented many valuable contrivances for the use of photographers.

First procure, at some chemical glass warehouse, a bottle of the form here shown. You will see that it has two openings; one in the usual place, and another on a level with the bottom. This last must be fitted with a good cork, with a hole through its centre. Into this hole is fitted a bent glass tube (glass tubing can easily be bent in the flame of a spirit-lamp), so that it will turn round in the cork, and can be bent down when required. The bottle must now be half filled with a saturated solution of sulphate of iron--made by pouring a pint of boiling water on to a pound of sulphate of iron. This must be done in a jug or earthenware vessel, for glass would not stand the sudden heat. When cool, the solution can be transferred to the bottle, into which is afterwards poured four ounces of paraffine oil. The paraffine floats on the top of the iron solution, and prevents any access of air which would spoil it. Hence the use of the little glass tube, by which small quantities can be drawn off as required.

In another bottle--this time an ordinary one--is placed a saturated solution of oxalate of potash. When we wish to develop a picture, we must take one part of the iron solution to five of the oxalate. This is poured on to the plate after its preliminary soaking in water, and the image will gradually grow out, and will acquire density without any further aid. It is fixed, as before, in the hyposulphite solution. Should a white sediment appear on the film, it is oxalate of lime from the hard water used. This can be easily dissolved by letting the plate remain for a few moments in a weak acid bath composed thus:-- Hydrochloric acid . . . . . . 1 drachm. Water. . . . . . . . . . . . .8 ounces.

I advise my readers to try both the methods of development here given and to adopt the one which they like best. In either case the picture must be varnished, as the gelatine film, although hard to the touch, is easily stained by contact with the printing paper, or by moisture of any kind. A good and cheap varnish can be made by adding to ordinary white hard varnish twice its bulk of methylated spirits of wine. This should be filtered through cotton wool in the way already recommended for the emulsion. The great advantage in using a paper funnel for such purposes is that, when done with it can be thrown away and easily replaced. The trouble of cleaning a glass funnel is thus avoided. Before being varnished, the plate should be warmed in front of a fire; it is then put on the pneumatic holder, and the varnish is flowed over it. The surplus is returned to the bottle, and the plate heated at the fire, and in a few seconds it is dry.

So far, I have described the method of producing a negative on glass. It now remains to explain how that negative can be utilised in producing any number of positive prints on paper. The lights in the negative are all dark, whilst the shadows are clear. If therefore we place this over a sheet of sensitive paper, the light will shine through the shadows, so as to make them dark as they should be, and the lights will be more or less protected by the denser parts of the film.

A frame will be necessary in which to place the negative backed by the sensitive paper. This frame can be bought, or can easily be made at home by any one who can handle a saw and hammer. Even a common wooden picture frame can be adapted to the purpose, but it is better, if possible, to make one out and out which will be really serviceable. First, make an ordinary wooden frame with a rabbet into which the glass fits. The best plan is to make the frame of the same size as the negatives we are in the habit of producing, so that they can at once be put within it. If it is made larger, a thick glass will be required on which the negative must be laid. The back of the frame is hinged, so that either half can be turned back and the print examined without removal. Upon the back rest two springs made of hard rolled brass, the end of which tuck under wire bridges.

Albumenised paper ready for printing can now be bought so cheaply that it is not advisable to sensitise it at home; an operation which is not only dirty, but expensive and unsatisfactory. The sheet, as supplied by the makers, is cut into convenient sizes and put away in yellow paper, when it will keep for several weeks.

Having placed the negative in the printing frame, glass side outwards, a piece of sensitised paper is laid upon it, then comes the cloth-covered back shut in with its brass springs, and the frame can be exposed to light, not direct sunlight, but upturned towards the sky on the shady side of the house. In from ten minutes to one hour, according to the weather, the paper will be printed sufficiently for further operation. It must be noted that the image must appear more dense than is actually required, for it loses much of its vigour in the subsequent processes. With two or three printing frames and sufficient negatives, an immense number of prints can be struck off in a few hours, provided the weather is suitable. In any case, it is better to print all that are required before proceeding to the next stages, which can be best carried out with the whole bulk.

First, then, immerse the pictures in water for ten minutes, change the water, and give them a second bath for the same time. They must now be transferred, two or three at a time, to the toning bath, where the red brick hue which they exhibit will be changed to a purple black. The toning bath is made thus:-- Chloride of gold . . . . 4 grains. Acetate of soda. . . . . 2 drachms. Water (distilled). . . . 1 pint.

This should be kept in a stone-ware bottle, or the light will cause the gold to precipitate in a metallic form. When in use, it is placed in a porcelain tray, and the prints should be moved about so that they may tone equally. Their progress may be ascertained by looking through them, when it is at once seen whether the change of colour has been thoroughly effected. Removed from the toning bath, the prints are once more placed in plain water, and finally into a fixing bath of hyposulphite of soda (four ounces to one pint of water). Complete fixation will be effected in about fifteen minutes, when the prints must be washed in several changes of water--indeed they are none the worse for remaining in the water all night--with a tap dripping upon them. The least trace of soda left in the prints will cause them rapidly to fade, and to want of care in this respect is the non-permanence of silver prints generally attributed. But fading is, I am certain, as often due to the composition of the paste or other material used for mounting, and also to the state of the cardboard itself on which the print is finally supported. I lately saw a beautiful photograph which was taken some years ago in Russia. It was mounted, and exhibited generally a yellow sickly hue. Another print from the same negative taken at the same time, but unmounted, was as clear and beautiful in colour as if it had just left the toning bath. I believe that, if due care be taken, silver prints will keep their tone, but unfortunately some of the conditions are beyond the control of the operator, and such prints have a bad name for want of permanence. These objections cannot be applied to the carbon printing process, a brief outline of which I will now endeavour to give. A certain class of chemical salts, of which bichromate of potassium may be taken as the type, has the property of making gelatine insoluble after exposure to light. Upon this property is based the carbon process now to be described. Carbon tissue as prepared and sold by the Autotype Company consists of thick paper faced with a coating of gelatine mixed with fine pigment of different colour according to the subject for which it is intended. The tissue must first be cut into convenient sizes, after which it is sensitised by floating in a bath of-- Bichromate of potassium . . . 15 grains. Water . . . . . . 1 ounce. Liquor ammonia . . . . 2 drops.

Enough of this bath should be made to completely cover the tissue, and it should be immersed until it lies perfectly flat, which it will do in about one minute. It is then removed and hung up to dry in a warm room, which must be dark or protected by yellow blinds. In about twelve hours it will be dry and ready for the printing frames, but it is in all cases advisable to dust the negative with a little French chalk in case the tissue should adhere to it. An opaque border of black paper should be pasted round the negative, so that the extreme edge of the tissue is not acted upon by the light. This precaution is a great help to the subsequent operations. The tissue being almost black, we cannot watch the process of printing; it is therefore usual to expose a silver print at the same time, by which we can judge as to the action of the light upon it.

While the print is proceeding, a glass plate must be prepared for its reception by being rubbed over with beeswax. Yellow beeswax . . . . . 1 grain. Methylated ether . . . . . 1 ounce.

This should be applied with a piece of flannel, and rubbed until there is no perceptible trace of it left; still, enough remains to serve the intended purpose. The plate is now coated with enamelling collodion, and when this is set, it is left in a basin of water. The exposed tissue is now soaked in the same water until it becomes limp, when its face is applied to the collodionised surface of the glass, and both are removed from the basin. It is now placed on a board and covered with a piece of American cloth, which can conveniently be nailed to the edge of the wood, so that it falls over its surface as a flap. The upper side of the cloth is now carefully rubbed with a squeegee--an indiarubber contrivance made for the purpose, and which on a larger scale is used for removing slush from the pavements of our streets. This rubbing causes the two surfaces of the collodion and tissue to adhere very closely. The plate is now put away for ten minutes with a weight above it, or if many plates are in course of development, they can be placed one above the other as they reach this stage. The actual development now begins. For this no chemicals are required, but simply hot water, that is to say, water just so hot that the hand can be immersed in it without inconvenience. Taking the first plate treated, it is placed in the warm water, and gently laved with the hand. Presently the pigment, unaltered by light and therefore still soluble, is seen oozing out beneath the paper, and in a few seconds the latter will come bodily away, leaving the picture in all its details upon the glass. In this state it can be mounted as a transparency for window decoration, or, if of suitable size, it can be finished as a lantern slide. But for preservation in an album or as an ordinary picture, it must be mounted upon paper.

For this purpose transfer paper is sold, which must be soaked in tepid water until it becomes tacky. It is then applied to the picture on the glass, with a little help from the squeegee, and the whole is left to dry. When dry, the picture will, if the beeswax operation has been properly performed, almost leave the glass of itself. If not, a knife edge applied to one corner will generally cause it to separate. The print must now be trimmed and mounted in the usual way. I may here mention that Glenfield starch freshly made is a far better mounting material than either flour-paste or gum. The first is liable to turn sour, and the second is messy and difficult to deal with. Starch, on the other hand, is clean and easy to use.

Another printing process which I have lately adopted, and which I think the most suitable for amateur hands, is that lately introduced by the Platinotype Company, of Bromley Road, Lee, London, S.E. The merits claimed for it are absolute permanence, the prints resisting all chemical agents with the one exception of hot "aqua regia"; its simplicity, rapidity of printing, and the extreme quickness of after operations. The paper, ready sensitised, is supplied only by the company, and it can be kept for any reasonable time in a tin case made for the purpose containing chloride of calcium. This acts as a drying agent in protecting the paper from the moisture of the atmosphere. The company give the following particulars relating to exposure and development:-- "The sensitised paper before exposure to light is of a lemon yellow colour. During exposure the parts affected by light become of a pale greyish-brown colour, and finally of an orange tint (sometimes very dingy). When the last change has occurred, it indicates that the iron salt has been completely deoxidised, so that further action of the light produces no more effect upon it. When printing from a negative having strong contrasts, it is frequently found that the deepest shadows of the print are of this orange tint, and are lighter in colour than the parts rather less exposed to light. "The correct exposure is ascertained by inspection of the paper in a very weak light in the usual manner. A little experience will enable the exposure to be determined very accurately. As soon as the exposure of each print is complete, it should be placed in a tin can or other suitable receptacle, containing a little dry chloride of calcium to preserve it from moisture until it is developed. Development should be conducted in a feeble white light, and may be proceeded with immediately after the print is exposed, or more conveniently at the end of the day's printing. The developer is made by dissolving 130 grains of oxalate of potash in each ounce of water. A large quantity of this solution may be made up, as it will keep indefinitely. The development is effected by floating the printed surface of the paper on this developing solution, which is conveniently contained in a flat-bottomed dish of enamelled iron, or of porcelain, supported on an iron tripod. A Bunsen lamp with rose burner to spread the flame forms the best means of supplying the heat, or a spirit lamp may be used. If a porcelain dish be adopted, care should be taken to prevent the flame from impinging directly upon it. "A temperature varying between 170deg. and 180deg. Fahr. may be considered the standard heat for the developer. The bottom of the dish should be covered with the developing solution to the depth of at least one-fourth of an inch. After the batch of prints has been developed, the solution should be put into a bottle for future use. Before again using this solution for developing, it should be decanted from any green crystals (of no value) which may have formed, and then enough fresh oxalate of potash solution should be added to it to bring it up to its original bulk. Large prints may be developed without any difficulty on a narrow dish or trough (having a length equal to the breadth of the print) by being slowly pulled over the solution contained therein. "The developed prints must now be washed in two baths of a weak solution of hydrochloric acid to clear them (1 part acid to 80 parts water). As soon as they have been removed from the developing dish, they should be immersed face downwards in the first bath of this acid, in which they should remain ten minutes, or rather less; they should then be removed to the second bath, in which they should remain for a like period. While the prints remain in these acid baths, they should be moved so that the solution has free access to their surfaces. On no account should the prints be placed in plain water on leaving the developer. "After the prints have passed through the two changes of acid, they must be rapidly rinsed, and then well washed in two or three changes of water during about half an hour. They are then finished. The object of this washing in acid and water is to remove the iron salt with which the paper is sensitised. These prints being on plain paper are better dried across glass rods or tubes. If wood rods or strings are used for the purpose, they should be kept very clean, otherwise stains are likely to occur. "There is very great latitude (from 100deg. to 180deg. Fahr. and upwards) allowable in the temperature of the developing solution. Over-exposed prints may frequently be saved by using a low temperature, and those under-exposed by using a high one. It is, however, advisable to give such exposures as will result in good prints when developed at a temperature of 170deg. Fahr., or thereabout; developing solutions at a low temperature frequently give granular results."

Such is the latest method of printing a photographic picture. Combined with the gelatino-bromide process as the means for taking a negative, it represents a wonderfully simple and easy manner of practising a most fascinating art. I feel quite sure that, if my readers will diligently follow the instructions here given, they will be able to produce pictures of which they need not be ashamed. As some sort of encouragement to them in their labours, I may remind them that the wonderful progress which the art of photography has seen within the last few years is mainly due to amateur workers. The gelatine process is no exception to the rule. It has in one form or other been practised by amateurs for many months. The professional photographer has, until lately, been prejudiced against it, and has stuck to the collodion process. At last, however, the productions of the new method have taken him by surprise, and gelatine plates at last find their way into the studio of every photographer who moves with the times. By their aid he is able to attempt subjects which in bygone days he would have deemed impossible. In the near future it will no doubt be possible to secure the image of the swiftest bird while on the wing, if not the picture of a moving cannon ball. This may seem like exaggeration, but from my experience of the gelatine process I feel confident that the only obstacle to such a result will be the mechanical difficulty of exposing the plate in the camera with the requisite rapidity.