The usual method of making photo-lithographic transfers is upon gelatine made sensitive with potassium bichromate. This is quite sensitive enough to daylight, or to electric light; but if transfers are required when neither day nor electric light is available, then bichromated gelatine is useless, and some other method is wanted. Try this: - Make a print upon any of the ordinary bromide papers of commerce, using a good negative from a subject in line, by artificial light; develop the image with alkaline pyro, then wash and place it upon the inking-board; next, blot off the water with a soft cloth, and dab all over with a sponge saturated with transfer ink thinned with turpentine: let the turpentine evaporate, then take a glue roller - i. e. a type-printer's roller, and roll until the whites are quite clear of ink. Now soak the print in the pyro again for a few seconds, and expose it to the light. Finally, wash free from pyro and hang the print up to dry. When the print is dry it is ready for the transferrer, who treats it the same as he would any other photo-lithographic transfer.

The only way to fail with this method is to over or under expose the print, or to use a bad negative. The negative must show perfectly clear lines. Some of the newer papers of commerce contain too little gelatine to succeed perfectly, therefore it is best to make th,e paper at home. It is not a very complicated process, as the colour of the image under the developer is not all-important. A good formula is Gelatine .. ... 800 gr Water ........... 30 oz.

When the gelatine is quite soft, melt it at 120° F., and add 320 gr. ammonium bromide; stir it until it is dissolved, then add 10 m. hydrochloric acid and stir well.

In 10 oz. water dissolve 450 gr. stiver nitrate, bringing this solution to the sime temperature as the gelatine solution; now proceed to pour the silver solution into the gelatine in a very thin stream, stirring it vigorously all the time. Strain it into a warm dish, and tilt the solution so that it is only along one end of the dish. Having made a small roll of the paper, lay one edge of the roll,upon the liquid, and as it curls take hold of it and lift it slowly up, when the paper will' unroll itself, and receive a nice even-coat of emulsion. Hang it up to dry, and repeat until all the emulsion is. used.

For half-tone transfers, use calcium bromide and chloride, with 200 gr. extra gelatine, drying the paper at as high a temperature as possible without melting the gelatine. Paper with this emulsion upon it. will be very hygroscopic, and must be kept very dry. Before use always dry the paper, and warm again before developing, so as to encourage the reticulation of the gelatine.

This paper is to be exposed under a half-tone negative, developed and washed, then inked up as directed-for the line transfers, followed by immersion in the developer, and subsequent exposure to light, washing, and drying. To transfer to stone, trim with a pair of long shears, then put it into the damping-book until quite limp; then sponge the back of the transfer with a ablution of oxalic acid 1 part, water 100. Take great care that none of this solution pets on the front of the transfer. Lay the sheet in position upon a cold, dry stone, and pull it through the press, with plenty of pressure, 5 or 6 times without lifting the tympan. The paper can be lifted off, leaving the image in ink on the stone. Gum it in, and leave it for 5-6 hours before rolling up. - • (W. T. Wilkinson.)

Albert Photolithographic Transfer Paper

Following is a detailed description of the photo-lithographic process in practical use in the most eminent printing establishments in Austria and Germany.

The bichromate bath consists of 1000 cc. water and 50 grm. potash bichromate. To this solution caustic ammonia is added until the reddish colour of the bath turns to a light-yellow colour; an excess of ammonia does no harm. The temperature of the bichromate bath should be about 66° F. It is filtered into a flat dish of sufficient size, and the paper, with the prepared surface up, is entirely immersed, and allowed to remain in the bath until it is quite soft. This is of importance, for if it is not soaked long enough, also if the temperature of the bath is below 66° F., the bichromate solution will not enter sufficiently into the prepared film, and consequently, at the subsequent inking up of the copies, the colour will adhere but badly to the exposed parts, especially to the broader lines and surfaces of the picture.

If sufficiently soaked, the paper is removed, held over the dish so that the fluid flows off only at one of the lower corners, and allowed to drain until the liquid only drops. Then the two corners of the paper, which have been held, are given to a second person, who now holds the sheet over a plate glass a little larger than the paper. This plate glass must previously be well cleaned, then rubbed in with talc powder, and the surplus of the latter dusted off with a broad soft brush. On this glass plate the sheet is placed with its lower edge on the prepared surface, and smoothed down by means of a soft cloth. During this operation, the person assisting holds fast the corners of the paper, until the mounting is finished, and only gives slowly way to the pressure of the smoothing down.

If too much of the talc powder has been dusted off the plate glass, it may happen that the paper, after drying, partly adheres to the glass, and even tears here and there; it is therefore necessary that a certain amount of talc powder remains on the plate, and better too much than too little. Should the paper, after entirely drying, still adhere to some parts of the glass, then the latter has been badly cleaned.

Care should also be taken that in smoothing down the paper no air-bubbles arise between the glass and the paper, since they will appear on the dry paper in the form of matt spots, which will interfere in the case of fine work. As soon as the sheet lies quite flat on the glass, the back of it is well rubbed with a soft cloth, applying thereby a certain degree of pressure to suck up the fluid on the hack of the paper, and also to squeeze out the bichromate bath between the paper and the glass, and by this means to accelerate the drying process.