PREPARATION of LANTERN SLIDES without a CAMERA' L. A. GOLDBLATTZAND JAMES E. BATES Erie Center, University of Pittsburgh, Erie, Pennsylvania
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N this paper, emphasis has been placed upon the
more convenient methods of preparing homemade slides, using the materials and equipment most commonly available. Probably the simplest slide to make is the ground glass slide. Ground glass can be inscribed with ordinary lead pencil or c ~ a y o n ,may ~ be erased or washed with soap and water and used repeatedly if desired. A very coarse form of ground glass can be purchased from almost any glazier. Such glass is sold by the square foot, and as the price is usually the same whether bought in large or small pieces, it is advantageous to purchase glass plates the size of the standard American slide, 3l/4" X 4". Use of a finer grade of ground glass, the so-called satin finish ground glass which is usually obtainable at the larger window glass supply houses or dealers in photographic supplies, permits finer lines and shading. The edges of such cut glass plates should be smoothed off or taped, for comfortable handling. Plain glass can be written on with India ink but the ink tends to crack or check with age. A homemade ink that writes reasonably well on glass can be prepared by dissolving three per cent of celluloid (or nitrate base photographic film) in methyl cellosolve and adding a suitable dye, e. g., malachite green. Plain glass can be colored very nicely with such lacquers. The suggestion has been made that plain glass can be coated with gelatin or lacquer and that such a coating will take ink better than plain glass itself, but there would seem to be easier ways of making glass slides. One is the use of old photographic slides from which the silver has been bleached out with dichromate leaving a clear, gelatin coated, glass slide. Commercial glass-marking inks are available and can be used to write directly on clear glass with an ordinary steel pen. Such writing is quite permanent and can be washed off only with considerable difficulty. The suggestion has also been made that for temporary use glass can be smoked over with a smoky flame and inscribed by means of a pencil or match stick. Such
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1 Based upon a paper presented before the Division of Chemical Education a t the ninety-seventh meeting of the A. C. S., Baltimore. Maryland. April 6 , 1939. 2 Present address: Bureau of Agricultural Chemistry and Eneineerin~.United States Denartment of Anriculture. Washington. D.-C. Dr. H. F. Halenz of Emmanuel Missionary College, Barium Springs, Michigan, suggests that the brilliancy and sharpness of such slides may be materially enhanced by coating the slide with a clear Lacquer.
a slide can be used repeatedly, as when projecting election returns. Thin sheets of transparent celluloid, cellulose acetate, ethofoil, etc., can be used instead of glass and can be inscribed with suitable inks.4 Such transparent sheeting can be inserted in a typewriter and typed directly or through carbon papers. Sharp impressions can be obtained by placing the piece of transparent sheeting inside a piece of carbon paper folded with the coated surfaces inside and typing with a displaced ribbon, as when cutting a stencil. Sheeting about 0.012" in thickness is usually stiff enough to remain upright unsupported in a projector, yet thin enough so that it can be typed conveniently. Such sheeting can be obtained directly from the manufacturers or from many stationery, hardware, or automobile supply stores and can easily be cut into 31/4"X 4" (slide size) piecess Inscriptions can be wiped off quite easily with a dry rag and the same blank plate can be used repeatedly. Of course this means that such slides will smudge rather easily also. If a permanent slide is desired, such writing should be protected by cover glasses. However, in that case it is probably preferable to use a thinner transparent sheeting such as cellophane or pliofilm. Such thin foil can be inscribed with ink or typed between carbon papers exactly like the heavier ~heeting.~One can cut one's own 5; and 10-cent store cellophane to lantern slide size, or cellophane sheets already cut to size may be purchased for as little as 500 sheets for a dollar. Commercial forms of such cellophane blanks previously fitted with mask and carbons and ready for typing can be purchased for from two to three cents each. Several shades are
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Mr. G. A. Dawson of the du Pont Film Mfg. Corp., Parlin, New Jersey, suggests the use of dyes such a s Iuduline base. Auramine base, Nigrosine, Pontalin Green B, etc., dissolved in methyl cellosolve. He states: "This is slow in drying but the drying can be speeded up by diluting with benzene or toluene or with ethylacetate, alcohol, or acetone. The last three solvents will increase the bite of the ink, but the first two will not affect the bite very much. The ink can be given more body, if that is desired, by dissolving in i t 2-3 per cent of film base (nitrate)." Several persons have inquired whether a celluloid slide will not become overheated if i t is allowed to remain in the projector too long. Pyralin slides have been allowed to remain exposed in a projector (Delineascope Model D, 500 watts, manufactured by the Spencer Lens Company of Buffalo, N. Y.) for a s long as half a n hour without any detectable change except, perhaps, for a slight discoloration. 6 Dr. Rufus D. Reed of Montclair State Teachers College, Upper Montclair. New Jersey, suggests that cellophaneroughened somewhat by rubbing with talcum powder may be inscribed readily with ordmary writing ink.
crowding in the center or the legend will not be legible. If pica type is used, not more than fifteen lines of thirty spaces each should be used on a single slide; if elite type is used, as many as sixteen lines of thirty-eight spaces each may be used. There is little danger of overcrowding a typed slide because even if 4ite type is used, the projected image should be legible if on a fairly large screen. A good working rule is this: No character on the screen should be smaller than one five-hundredth of the distance to the most distant spectator. Material which is already available in black and white, as in a book or typed page, can be very readily copied photographically. Two classes of such material may be distinguished: first, that in which the copy is not as large as a standard slide and, second, that in which the copy is larger than a slide. In the first case, two situations may be treated separately; lirst, if the material is printed on only one side of the page, and, second, if both sides are printed. In the 6rst case, where the material to be copied is not as large as a standard slide and is printed on only one side, the extremely simple method of transmission can be used. In this case, a paper negative is made by passing light through the printed page onto a piece of photographic paper. This is developed and then printed onto a film or photographic slide to make a positive transparency. Thus, in one specific case, a paper negative was made using Velox F-5 paper. The sensitized paper was placed emulsion side up and the material to be copied placed in contact with the emnlFIGURE 1.-REPLECTIONMETHOD OR PHOTOGRAPHIC REPRODUCTION sion. These were pressed together tightly with a heavily weighted piece of plate glass. Intimate contact available. Amber is said to be easier on the eyes of between the @per and the material to be copied is essential. the spectator. Such thin films will not remain upright The upper blank surface of the page to be copied was unsupported in a projector, but may be sandwiched then illuminated with a type A Photoflood bulb held between two plain cover glasses, hinged with adhesive in a desk lamp a t a distance of two feet. (The light paper or scotch tape. therefore passed through the glass plate, then through A finished binding may be obt'ained by using ad- the blank side of the page, then through the printed hesive paper or scotch tape. To make such a per- side of the page, finally striking the sensitized emulsion manent binding, cut off a 15-inch length, place this flat on a table, and holding the two cover glasses firmly together, place one edge in the middle of the binder and rotate the slide along the tape, keeping the edges in the middle of the tape. Crease the tape down over the edges of the glasses, reserving the comers until the last. A simpler binding, sufficient for all ordinary circumstances, is made by simply fixing two short pieces of tape to a slide, one on either end. It is customary to place a tab on the front, upper right comer of the slide as it will be placed in the projector. Such a marker (suitably a punching from a piece of gummed paper) should be placed on the lower left corner of the slide when it is held in a position to b e read normally. There exists an apparently almost uncontrollable tendency on the part of exhibitors to attempt to put too much material on a single slide. The whole area of a slide cannot be projected and ample margins FIGURE 2.-DIRECT CONTACT COPY(REFLECTION METROD) should be allowed. Nor should there be too much A N D ITS POSITIVE ON PAPER
of the Velox paper.) After exposure of 45 seconds, the paper was developed,' fixed, dried, and printed on Eastman Process Film. (Unfortunately Process Film is not sold in slide size, but the 31/r" X 4'/&" size may be purchased and cut to size, or the 8" X 10' sheets may be cut into six pieces and the trimmings used as test strips to determine proper exposures.) The positive transparency is made exactly as in printing a paper positive, i. e., the emulsion side of the lilm is placed in intimate contact with the emulsion side of
(The legend indicates the length of exposure of negative and positive. Thus N100P15 means that the negative was exposed for 100 seconds and the positive printed for 15seconds.)
the negative and light is passed through first the negative (in this case a paper negative) onto the positive (in this case a film positiv$). A 15-second exposure to the light from a 7l/~-wattbulb a t a distance of two feet was adequate. The fdm was processed in the normal fashion to produce the finished film positive. This was then sandwiched between glass plates to produce the completed slide. If the material to be copied is printed on both sides the transmission method cannot be used. However, a reflection method can be used in this case (Figure 1). A piece of black paper is placed beneath the under side of the page to be copied. Velox paper is placed emulsion side down, directly in contact with the material to be copied, and pressed down firmly with a weighted glass. This is then illuminated with a Photoflood. Here the light passes through the glass plate, strikes the rear of the Velox paper; some passes through The developer used in all cases, both for paper and film, was Eastman D-72. This may be obtained in package form ready for solution or may be compounded from the published formula. Developingwascontinuedfor the timesuggested by the Eastman Company for the particular film or paper used.
the paper to the emulsion, continues on to the printed page beneath, and is reflected back from the white portions of the printed page. This reinforces the effect produced on the sensitized emulsion on the f i s t passage. This method seems to owe its success primarily to the induction period which characterizes photographic emulsions. When this exposed paper is developed, a mirror-image paper negative is obtained. (See Figure 2.) This may then be printed to produce a positive transparency or slide. In a tmical case a Velox F-5 oaoer negative made bv , an 11-second exposure to a Photoflood in a desk lamp a t a distance of two feet was processed and printed on Eastman Process Film by a 15-second exposure to a 71/%-wattlamp held a t a distance of three feet. The reflection method can also be used if the material to be copied is printed on only one side and has one advantage over the transmission method. The length of exposure in making the negative by the reflection method is quite uniform, depending primarily upon the type of sensitized paper used. For Velox F-5, this is about ten seconds, but the exposure time is not very critical and may safely be varied by about 20 per cent. In the case of the transmission method, the length of exposure varies with the opacity of the page to be copied and may vary from ten to sixty seconds. A moderate amount of over- or underexposure of the negative can be corrected in printing the positive but this requires some experimentation. If the material to be copied is larger than a slide some method of reduction is necessary, but the projector itself may be used as a copying-camera. A previously prepared slide is focused on.the material to be copied and the projector lens is stopped down with a pierced cork. The light from the projector is turned off, the slide replaced by a piece of photographic paper or film held between cover glasses or an unexposed lantern slide, emulsion side toward the.object to be copied. This is then illuminated with a Photoflood in a desk lamp held as level with the projector lens and copy as possible. If the copy is printed on very glossy paper or is badly wrinkled, it may be necessary to use two lamps a t an angle of 45 degrees. A glossy or highly reflective surface requires a shorter exposure. In a typical case, the projector lens was stopped down with a cork bored with a No. 7 cork borer and masked with a piece of black paper pierced with a No. 5 cork borer. This produced a sharp hole nine millimeters in diameter and, effectively, a lens opening nine millimeters in diameter. News Bromide paper was used for the negative and given an exposure of 150 seconds to a Photoflood held in a desk lamp a t a distance of three feet. This was then processed and printed on Process Film by a 12-second exposure to a 71/2-watt lamp a t a distance of three feet. Bromide paper and Process Film have about the Same emulsfoi speed but Process Film is about Z1/2 times as fastas Eastman Contrast Slides. That is, requires about times as long exposure. Exposure time is not at all critical and poor
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timing can often be corrected in printing. However, some experimentation will be necessary to familiarize oneself with the effect of various exposures. For this, Bromide paper may well be used as i t is considerably cheaper than film. With a recommended procedure for testing, a wide latitude of exposures is permissible. In one case, Process Film was used, two-thirds of the copy was covered with black paper and illuminated for 50 seconds, then another third was uncovered and the whole again illuminated for 25 seconds and finally the remaining third was uncovered and the whole illuminated for another 25 seconds. This resulted in an exposure of three vertical strips on Process Film for 100. 50, and 25 seconds. This was then processed and printed on Process Film, but the printing was varied by using horizontal blocking strips and allowing 15, 30, and 60 seconds for printing exposures. (In testing, successive exposures should in all cases be a t least doubled as smaller variations are not significant.) That exposure time is not a t all critical, may be seen from the fact that in Figure 3 either the lower left portion or the upper middle portion would produce acceptable slides, yet in the, one case the negative received an exposure of 100 seconds and the positive 60 seconds, whereas in the other case the negative was exposed for 50 seconds and the positive for 15 seconds. Film or slides can, of course, be used for making the negative and the negative can itself be used fairly satisfactorily for projection to small groups if the negative is somewhat underexposed. Typically, an Eastman Contrast Slide, exposed for 20 seconds to a Photoflood a t a distance of three feet, produced a light negative which could be used directly as a lantern slide. The advantage is that the time and cost of the second step of converting the negative to a positive are eliminated; the disadvantage is that the image is rather dark and not too clearly legible when projected for long distances.
FIGUKE 5.-CLOSEUP TOR IVHEN
STOPPED DOWNLENSO N THE PROJECUSED A S A COPYING CAMERA
OF
Direct positives can be made by reversal also-that is, by exposure, developing (as in D-72), bleaching in a chromate bath, clearing with bisulfite, re-exposing, redeveloping, and fixing. This will produce a fairly satisfactory positive image directly. If material is to be typed and then transferred to a slide, it is convenient to use the impression from white "carbon" paper on black paper, photograph that and develop and fix in the normal fashion to produce a black-on-white positive transparency directly. Film slides can be prepared by using a projector as a camera (Figure 4), either by masking out all but a 2" X 2" portion gf the slide area of a standard projector (Figure 5) or by using the regulation 2" X 2" projector itself as a camera. Surprisingly enough, a somewhat shorter exposure time is required in making the smaller slides (even when using the large projector and mask as a camera) than in making the larger slides. The film strips obtainable from Bibliofilm Service, Washington, D. C., can be mounted separately and make satisfactory slides. Dufay color pictures may also be taken, using a projector as a camera. The particular advantage of this method (over Kodachrome, for example) is that pictures may be taken in convenient slide size and processed immediately. Such color slides are not entirely satisfactory and much of the color obtained on projection depends upon the nature of the screen and the projector used. BIBLIOGRAPHY
FIGURE 4.-SETUPSHOWING PROJECTOR USED CAMERA
AS A
COPYING
ALYEA,"Lantern slide technics," J. CHEM.Eouc.. 16,308-12 (1939). ASTELL, "Significant aspects of visual aids in chemical education," ibid.. 16, 129-33 (1939). This contains an extensive bibliography including about a dozen references to methods for preparing slides. B o ~ n s r o"Simple ~, and important photographic method of copying at nominal cost." RN. Sci. Imtr.. 9,328 (1938). "Lantern slides from typewritten material," CARPENTER, Science, 89, 372 (1939). HAMILTON, "HOWto make lantern slides," Keystone View Company. Meadville. Pa., 1938.
