The Optical Magic Lantern Journal (March 1902)

144 The Optical Magic Lantern Journal and Photographic Enlarger. When employing the wet collodion process, unless steps be taken to make the film adhere to the glass, it is not unusual for the film during the washing process to suddenly leave the glass and disappear down the sink. To obviate this inconvenience, before coating the plates they should be albumenised as follows :— Beat the white of an egg to a froth, and add a pint of water; insert a piece of cotton woolin a funnel, then pour in some of the albumen solution. Take the plates one by one, after having been thoroughly cleaned, and whilst wet run the lower end of the funnel along one of the edges, and incline so that the albumen will run over the plate, driving the water before it. Place in a rack till dry, then coat with collodion as required. The film will never part from the glass during the various manipulations. Bells, knocks, ‘‘ next slide, please,’ coloured light at desk, and various other devices have been used aS a means of communication between the lecturer and operator when it was | reguired to change a slide; but perhaps the neatest device which we have witnessed was some years ago, when the operator had a small ! electric lamp placed close to the box containing the slides. By means of a small accumulator and some wire provided with a push, the lecturer simply brought the latter into play, and kept the light on for a few seconds. As soon as the light appeared the operator Should it at any time be found that it is impossible to make sufficient connection between the fittings and a cylinder of compressed gas, owing to the abrasions at the metallic connecting surfaces, the intervention of a thin washer of lead will remedy matters. It may not be generally known that gas cylinders are slightly larger when fully charged with gas than when empty. If one has a metal ring, which will only just go on the cylinder when empty, it cannot be placed on when full. The lenses of a condenser should always be so mounted in their cells that when shaken they will rattle. If they be secured tightly in their cells or cell bound, the heat from the illuminant will cause the glass to expand and the condenser to crack. In many American lanterns the glasses are merely held in position by three spring clips secured to the brass mount. All rubber tubing in connection with lanterns should be of the very best; the cheap kind soon comes to grief and costs more in the end. : Some years ago it was the rule to use tubing changed the slide, and was also enabled to scan | the next slide from the box to make sure that all was right. Announcement slides may be made by means of the typewriter, using transparent gelatine paper. with an inside spiral wire, but experience has taught that this wire soon rusts and breaks, thereby causing damage to the rubber. From time to time experiments have been made with lime obtained both at home and ' abroad, in order to ascertain which gave the ' best results with the oxyhydrogen flame, but it : is generally admitted that lime obtained from certain parts of Ireland is as good if not better . than that obtainable elsewhere, and it is from The ink will be found to be somewhat ; translucent, but this may be obviated if, whilst | the writing is fresh, it is dusted over with ; powdered chalk. It would appear at first sight that if house this source that most lime cylinder makers in Great Britain get their supplies. It is important that all dissolving taps should , occasionally be cleaned to ensure good results. gas be compressed in a cylinder, it could be | used in conjunction with an incandescent gas | mantle; but the mantle only gives off a respect| able light for a short time, after which it rapidly darkens, and its light-giving properties fail, leaving little more than a redness. Pops when using ether saturators generally be traced to too low a pressure of gas. | When a saturator is rather tightly stuffed, the spring in the regulator at cylinder may require to be seen to, or a stronger one substituted. Yet how seldom does the lanternist think of attending to this. The plug should be removed once a season, well cleaned and lubricated with a mere touch of vaseline. Brilliant diagrammatic slides may be quickly | prepared if the lanternist will keep a few cover | glasses, prepared as follows, in his outfit. may | Make a weak solution of Canada balsam in benzine, then pour it over the glasses and allow to dry. Ordinary ink and pen can be used on this surface for making either diagrams or announce ; ments.