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CH. VIII] PREPARATION OF LANTERN SLIDES 215
3. Cardboard at 45 degrees, lighted by a 40 watt mazda lamp above the cardboard 30 seconds.
4. Cardboard at 45 degrees with a 16 candle-power frosted bulb above the cardboard 120 seconds.
For contact printing with the same negative, 30 cm. (12 in.) from the light, if artificial, the following times sufficed: Diffused daylight, 2 sec.; Mazda, 40 watt lamp, i sec.; Frosted bulb, 16 c.p. lamp, 10 sec.; Petroleum lamp, 10 sec.; Gas mantle, 5 sec.
§ 332. Rapid preparation of lantern slides. — It occasionally happens that one needs a lantern slide at very short notice. In such a case, the negative can be taken and fixed in the hypo, rinsed in water, and put into the camera and a lantern slide exposed (§ 329). Then the negative can be washed as usual. The lantern slide is then developed and fixed, and washed a few minutes in water. It is then placed a few moments in 95% alcohol or denatured alcohol for dehydration. After removal from the alcohol it is dried in a draught or in the current of an electric fan. Negatives can be quickly dried in the same way. One can then make contact prints.
§ 333. Type written lantern slides. — It frequently happens that one desires to project some statement or some table. This can be written as stated above (§ 316, 321), or the statement or table can be made neatly with a typewriter, using a black ribbon. Then this can be used just as any other printed matter and a photographic lantern slide made from it.
If in a great hurry one can use the negative form of lantern slide and dry quickly (§ 332). This will give white letters on a black ground (§ 329a). (For film slides see § 333a).
§ 333a. Film lantern slides. — There has been recently introduced by the Eastman Kodak Co., a method of producing lantern slides on celluloid films, comparable to film negatives. The celluloid film is quite thick. There must be a negative as for glass lantern slides. The film is used in place of a lantern-slide plate. The printing is like printing cyco, velox or other paper. When the lantern-slide film is dry, after being developed and washed like a film negative, it is varnished and placed between two pieces of paper with the proper opening for the picture.
Naturally, these film slides are very light and are not fragile. Unfortunately the substance of which the film is composed is inflammable, and therefore the