LANTERN SLIDE PRINTING FRAMES.
8 1/2 X 6 1/2. It consists of a flat board covered with cloth, against which the surface of the negative is held by two rubber-covered brass springs. A hole in the centre of the board which holds the lantern plate allows of any desired portion of the negative being adjusted in position, after which the lantern plate is inserted with its film in contact with the negative, and a solid back is dropped into the opening and held with a spring. The exposure is then made by holding the frame at the distance selected for the requisite time.
For our own use we like warm-toned slides, and these are generally in favour at the present day. When we suggest making up 4 bottles of solution, we shall doubtless frighten some of our readers who fancy their shelves are already overburdened, but we would point out the solutions are concentrated, and will keep good for a long time. For those who want the best results the making up, perhaps once a year, of these four simple solutions is not a very serious matter. The favoured formula is one used by Mr. F. P. Cembrano, the quality of whose slides has never been surpassed. No. 1. Label bottle 10% Pyro.
A LANTERN SLIDE DEVELOPER.
Pyrogallic acid ............
Sulphite of soda............
Citric acid ..............
Water to ..............
No. 2. Label bottle 10% Bromide.
Potassium bromide ..........
No. 3. Label bottle Ammonium Carbonate 10%.
Ammonium carbonate (clear crystals)
No. 4. Label bottle Potash Hydrate 10%.
Water to ..............
Once made up these solutions will keep good for a year, and very little is used for each plate.
The exposure when using such plates as Paget Slow Lantern will be about 30 seconds with the frame at a distance of 12 inches from a 16 c.p. electric glow lamp. An initial trial may be made to test the light and to form a standard for future comparison, and for this
purpose we make trial exposures by uncovering the plate in strips. A piece of card over the surface of the printing frame will suffice and this should be successively withdrawn, so that a quarter of the negative is first exposed for 40 seconds, then, withdrawing the card another quarter, an exposure is given for 20 seconds, a third quarter has an exposure of 10 seconds, and now removing the card altogether a final exposure is given also of 10 seconds. Our lantern plate will now be exposed in four strips which have had exposures of 10, 20, 40 and 80 seconds respectively, and this when developed will show which exposure gives the best result.
The time taken to develop gives an excellent clue as to whether the exposure is correct, and we recommend that the exposure should be so arranged that the development always takes about the same time.
Before proceeding to develop compound the developer as follows : To each ounce of water add DEVELOPMENT.
The image should appear in 20 seconds and development should be completed in 80 or 90 seconds. These times are important, for if the slide is not ready in the time mentioned the result will be hard and unsatisfactory, and will show exposure has been insufficient. On the other hand, if the image appears before the time mentioned, the result will probably show over-exposure and the time must be reduced.
After rinsing quickly we fix in a bath of - Hyposulphite of Soda, 5 ozs., Metabisulphite of Soda or Potash, 1 oz., Water to 20 ounces.
Some makers object to the Metabisulphite because it has perhaps a tendency to make the colour somewhat cooler, but we have never found any disadvantage from its use, while it decidedly hardens the film and stops development.
The plate after fixing should be washed for 20 or 30 minutes in running water - preferably in a tank in which the water is syphoned out from the bottom. It should then be carefully wiped over the surface with a moist plug of cotton wool, or failing this the ball of the finger,
the water playing on the surface at the same time. This is to remove lime salts or other deposits frequently found in tap water.
We strongly suggest hardening the film with a solution of formalin before drying, if only to preserve the slide, for very often slides are ruined in the lantern the first time of using should the film be not thoroughly hard and dry. For this purpose formalin will be found most useful, for it not only preserves the film, but enables the plate to be dried quickly by heat, thus lessening the chance of it being spoilt by dust. The plate is, therefore, after washing placed for 10 minutes in a solution of after which it is washed again for five minutes and then dried.