Page:Popular Science Monthly Volume 91.djvu/162

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��Popular Science Monthly

��A Coating Which Gives the Appearance of Stone to Wood

TO make imitation stone for outdoor furniture, sun-dials, flower pots, etc., the following can be used:

10 parts lime 12 parts rosin I part linseed oil

Dissolve ingredients thoroughly and ap- ply the mixture while hot to the wood as a coating. The result will be an attrac- tive stone-like appearance that will last indefinitely. — L. E. Fetter.

A Special Ladder for Use in Boiler Shops

THE type of ladder illustrated is especially made for use in boiler and car shops where it is necessary to climb up to moderate heights for doing work. Being of the A-type it can be used like a painter's ladder and a plank can be put between two of them to form a trestle which will ac- commodate more than one workman. This method of construction makes the best pos- sible ladder — strong, safe and economical. It is built of short pieces of i3^-in. pipe, each about 21 ]/% in. long, which may be picked up about any shop where con- siderable pipe is used, such short pieces being useless for general work.

��% XI BRAS5 TEES

���V&BOLT THROUGH, £ RUNGS RIVETED %VER AT NUT

���An A-shaped ladder made of short lengths of gas pipe and fittings for a boiler shop

The pipes forming the rungs are 1 in. in diameter. In the making of the ladders illustrated, sixteen 1% in. by 1 in., brass tees and eight %-in. bolts, one for each rung,

��were used in each ladder. The parts were hinged at the top and pointed irons were fitted in the lower ends as shown. A chain is used between the parts to keep them from spreading.

While this ladder is very heavy, yet for the usage to which it will be subjected the construction is most desirable and at the same time inexpensive. — Joseph K. Long.

��Three Plates and Three Color Screens Used in New Color Photography

IN a recent patent on color photography there is brought out a process whereby three sensitive plates are placed together in such a way that the color screens in in them produce the desired effect on the plate.

Tn nhtain OPAQUE BACK SCREEN.

10 o Drain carrier class

these results it red-sensitive coatin&| is necessary to have all plates red color-screen- that are used ^-se nsitive coati in sets, sensi- tized at the

same time so yellow color-screen bame urae, bo blue-sensitive coating that they will age the same and have the same emulsion.

��carrier GLASS -

���Arrangement of plates in pack to record natural colors

��The ordinary dry plate is sensitive to the blue rays. In making up the sets green- sensitive plates must be used, which are sensitized with a chemical dye. A batch of these plates is divided into two parts, the first portion being coated on the back with opaque substance and allowed to dry, after which they are treated for rendering them red-sensitive. In the meantime, the second portion of the plates, which are already green-sensitive, are superficially coated with a temporary green. Then they are assembled to form a plate pack, and if desired, a blue-sensitive is combined with them. By securing these together they make a unit which may be exposed in any desired manner. After exposure the plates are separated, developed and fixed.

The chemical dye which gives a plate sensitiveness for a given color may be termed a color-sensitized agent and the plate a dye-sensitized plate. The green- sensitizing agent is preferably included in the original emulsion. The illustration shows the sensitive plates and their arrange- ment in a pack to record the natural colors as the rays fall, upon them successively from the camera-lens.

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