The Optical Magic Lantern Journal (June 1892)

68 comparatively soft, the other very hard. The marks of the soft pencil can be easily washed out with benzine, and it isto be used first. This “soft? pencil is far too hard for drawing on paper. It isa H H H H ofthe best quality; the hard pencil is a wood engraver’s six H, and this one, at any rate, must be a sixpenny pencil, for threepenny pencils will not make nearly so good an outline. 1 like Cohen's pencils the best, for the marks of Cohen’s H H H H are easily removed by benzine, leaving: the six H marks almost untouched. even better pencils than Cohen’s, but benzine will not remove the marks which they make. Rowney’s are not adapted for the purpose. It need hardly be said that the points of one’s pencils must always be kept as sharp as aneedle. ‘To do this requires practice, and the aid of a good pencil-sharpener is not to be despised. How will you copy your large picture on to the three-inch lantern slide? If you are drawing from nature, of course you will do it in the ordinary way. If you draw froma larger picture or from the microscope, exactness may be attained | by the old way of squares ruled over both the slide andthecopy. But instead of actually ruling the slide itself, make a little square of cardboard. On this draw a circle three inches across. this very exactly with three-sixteenths of an inch squares ; that is, divide it into such a number of squares that they count sixteen each way. (See figure). For drawing from the microscope, get an optician to make you what is known as an ““eyepiece micrometer,” only have it ruled in squares sixteen each way, like the figure. For drawing me] TTY CN LE PS S4e eR SRR Ree LATIN TTT TAT IN| tert tt Figure of card three-fourth inches square and ruled with three-sixteenth inches square on which to lay the lantern slide. Four matches at the sides to keep it in position. ‘Tracing papers of different sizes are to be ruled in the same manner. Winsor and Newton’s H H HH are} The Optioal Magio Lantera Journal and Photographio Enlarger. | from pictures, make a series of about a dozen tracing papers (ordinary transparent oiled tracing paper ) the smallest three and a-half inches across, the second, four inches; the third, four anda-half inches, and so on. Each tracing square and the ‘card for the slide should be inscriped with a circle, and also with two diagonal lines from corner to corner, Crossing at the centre as shown. Place a tracing paper on the picture to be copied ‘and the glass on the card—tour matches glued to ' the edges of the square on the card will keep it _in position. If you have a dozen of these tracing papers, as described above, you can easily choose one of such a size as to suit the picture exactly. The paper must be kept flat to the picture by a plate ot glass laid on it, and thenyou can make an outline with avery near approach to exactness. i The “first outline must be made with the 4-H pencil. Then remove the slide from the card and the tracing paper from the picture, and mend the outline with the same pencil. Any incorrect strokes may be erased by rubbing with a small hog-hair paint-brush moistened with benzine. Then go over the outline carefully and firmly with the 6-H pencil. Finally pour a little benzine on the slide, and rub it | gently with the finger until all the marks ot the Rule | 4-H pencil are removed, and a clear very thin , outline of 6-H pencil marks alone remains. It ; the benzine will not remove all the 4-H marks. in any place where the paint will be thin, or absent altogether, they may be quite removed by a point of “ink eraser” (artificial india-rubber) moistened with water. : ( To be continued, ) 0: Mounting Paste for Lantern Slides.* By M. V. PoRTMAN. For attaching lantern slide bindings to the glass nothing is better than bichromated paste, wnich is used for attaching paper to glass in the manufacture of electric instruments, and which is a most useful paste for many purposes in damp. climates. It is made as follows :— Flour ... 2 tea-spoonfuls Water,.. 7 wae 402s. Bicromate of Potash... 5 grains The flour must be rubbed to a smooth paste with the watet, then placed in a saucepan over the fire and kept stirred until it boils. Add the _ bichromate slowly, stirring all the time; then stand to cool. This paste must be kept in the dark and used as soon as possible. Soak the paper in it and attach to the glass, then place in direct sunlight foraday. This sets up a chemical change in the bichromate and renders the paste insoluble. * Journal of the Pnotographic Society of India,