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Lantern Slides

gas, time, plates, exposure, negative, contact and negatives

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LANTERN SLIDES.

slides by the dry-plate process are made either by contact printing or by reduction in a reducing camera. In the latter case the slides can be made direct from any larger ative, provided that the negative is not too large to be used in the reducing camera. In making lantern slides by contact, the most convenient size for the negative is a quarter size, although slides can be made by contact from larger negatives in those cases where only a portion of the negative is required to be copied. As the simplest method of making slides is by contact, we will confine our present observations to a description of that process. Lantern slides are made on plates specially prepared on thin glass 3Yi. x 4 inches in size. They are usually made in the ing by lamp or gas-light, and in the ordinary printing-frames. They can be printed by daylight, but, as that light is so much stronger than artificial light the slides print in a much quicker time, and consequently the danger of over or under-exposing is very much increased. Where gas-light is available we much fer that, but in places or towns where there is no gas, what is known as a No. 2 kerosene burner will take its place. In using gas-light care should be taken to maintain as even a sure in the gas, and consequently as even a brilliancy in the light, as possible. To do this the gas burner should be unscrewed and a little wad of fine cotton wool inserted, which will somewhat check the flow of gas and allow it to burn with a more even flame. Should we not do this the gas is liable to flare up at times, from too great pressure in the main, and give more light than we should expect, thereby tending to over-expose the plates. In printing the slides the negative is placed in the printing frame as in ordinary paper printing, and the thin plate placed upon it, with the two film sides in contact. Care should be taken to see that there is no dust on either of the two plates when they are thus placed in contact. It is well also to place back of the slide a piece of black cloth, cut to the proper size. The frame being filled, (and it is perfectly safe to fill the frames with these plates while the gas is turned down to a blue flame) it is held in the hand on a level with the gas jet, and about eighteen or twenty inches from it, and the gas quickly turned up. The time required for the exposure will depend upon the

quality of the negative. This time may vary from two seconds to twenty seconds. In practice we have found the general time to be about seven seconds. In making slides with a kerosene lamp,the printing-frame should be covered with the focusing cloth, which can be removed at the moment of exposure and replaced immediately at the close. After making a few dozen slides it will be found that the appearance of the negative, while being ex posed to the gas-light, will indicate the proper time. Experience will teach this accurately, as well as the exposure of plates in ordinary landscape photography. Very intense negatives, will, of course, require longer exposure, and can be held a little nearer the light; very thin negatives should have a sheet of white tissue paper on the printing frame which will considerably increase the time of exposure. A very thin negative will also make a good slide if the frame, in exposing to the gas, is covered with a sheet of yellow or orange glass. In this case the exposure will need to be six to eight times as long as usual. It has been our expe rience that negatives developed with hy-drochinon are the most even printers in regard to time. Negatives developed with pyro are extremely uneven, varying from very quick to very slow printers, while negatives developed with ferrous-oxalate are usually quick printers.

After the exposure has been made, the exposed plates can be immediately developed, or can be placed in a box, and a number of other plates can be similarly exposed. For the development we have a choice of several different developers, all of which are good. We can use either hydrochinou, pyro, ferrous-oxalate or eikonogen. As we think the hydrochinon developer is the safest for the beginner to use, we will use that for our first slides. The following formula we have found always to work well on lantern slides.

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