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The photographic news
- Bandzählung
- 27.1883
- Erscheinungsdatum
- 1883
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- Englisch
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- F 135
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- Hochschule für Grafik und Buchkunst Leipzig
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 1290, May 25, 1883
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Zeitschrift
The photographic news
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Band
Band 27.1883
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- Titelblatt Titelblatt I
- Register Index III
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Band
Band 27.1883
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- Titel
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May 25, 1883.] THE PHOTOGRAPHIC NEWS. 333 PAPER Over the gasket is laid a sheet of the thinnest grade of what is called pure rubber or elastic • Continued from page 285. STRAP IRON — RUBBER GASKET7 COTTON FLANNEL i etu STHINNEST PURE -eTARUBBER -THIN PAPER miserable plight, Messrs. Shadowcatcher and Fixedit des pairingly returned to town, the latter’s garments being pretty much of an Indian pattern, as far as symmetry of cut. Perhaps the worst part was the pantaloons ; all that was left of them hung leisurely down the back of his legs, and the greatest comfort to him was the knowledge that the first store on entering the town was for the sale of ready made clothing. flatten all cockles must be had at every part of the sensitized paper, and that, if the comparatively thin, inexpensive, light weight, commercial plate glass is to be used, it is desirable to have a pressure nowhere much greater than is nee led for that purpose, lest the fragile glass should be fractured by it. In each of my large frames I use the commercial plate glass; instead of the cushion of cotton flannel, or of flannel, I use a cushion filled which proved to be very slight. The wooden back-board, as constructed, is made in one piece containing no wide cracks. It has laid upon it some thick brown Manilla paper, the upper surface of which has been previously shellacked to make it en tirely air-tight. Upon this shellacked surface is laid a single thickness of thin paper of any kind; even newspaper will answer. Its object is simply to prevent the sheet rubber, which forms the APPARATUS FOR PRINTING BY THE BLUE PROCESS. BY CHANNING WHITAKER. * gum. Above this, and over the gasket, is placed a single thick ness of cotton cloth, of the same dimensions as the gasket, and yet above this are strips of ordinary strap iron, an inch and a half wide and nearly one-eighth of an inch thick. These strips are filed square at the ends and butt against each other at right angles. As the edges of the strips aie slightly rounded, they are filed .... e „ . „ . A . „ ,, . away sufficiently to form good joints wherever the others butt with air of sufficiently high pressure to flatten all cockles, and against them. The whole combination is bound together by to press all parts of the sensitized paper closely against thenega- ordinary stove bolls one-quarter of an inch in diameter placed tive ; and instead of the hinged back-board I use a back-board near the centre of the width of iron strips, and at a distance apart made in one piece and clamped to the frame of the glass at its of about two and one-half inches. Their heads are countersunk edges. Connected with the cushion is a pressure gauge, and into the strap iron. In making the holes for the stove bolts a tube with a cock, for charging the cushion with air from the through the thin rubber, care should be taken to make them suf- lungs. Experience shows what pressure is necessary with any ficiently large to enable the bolt to pass through without touch, given paper, and the gauge enables one to know that the pres- ing the rubber, otherwise the rubber may cling to the bolts, and, sure is neither deficient nor in excess of that which is safe for if they are turned in their holes, the rubber may be torn near the the glass. bolts, and made to leak. A rough washer, under each nut, pre- The Conslructwn of the Air-Cushion.—The expense of such | vents it from cutting into the back-board. For the purpose of introducing air to, or removing air from, the pad, a three-eighths of an inch lock nut nipple is introduced through the back board, and shellacked paper, and its thin paper covering. Without the back-board a T connects with the nipple. One of its branches leads, by a rubber tube, to the pressure gauge, which is a U-tube of glass containing mercury. The other branch has upon it an ordinary plug cock, and, beyond this, a rubber tube terminating in a glass mouth-piece. When it is desired to inflate the air-cushion, it is only necessary to blow into the mouth piece. A pressure of one inch of mercury is sufficient for any work that I have yet undertaken. With particularly I good paper, a lower pressure is sufficient. Upon the top of the pad is laid a piece of common cotton flannel with the nap out ward, and with its edges, tacked along the under-edge of the back-board. The cotton flannel is not drawn tight across the top of the pad. The reason for employing a cotton flannel covering is this; when the sheet rubber has been exposed for a few days to the strong sunlight, it loses its strength and becomes worthless. The cotton flannel is a protection against the destruction of the rubber by the sunlight. I first observed this destruction while experimenting with a cheap and convenient form of gauge. I used, as an inexpensive gauge, an ordinary t y balloon, and I could tell, with sufficient accuracy, how much pressure I had applied, by the swelling of the balloon. This balloon ruptured from some unknown cause, and I made a substitute for it out of I a round sheet of thin flat rubber, gathered all around the circum- -' PLAN . COTTON FLANNEL REMOYED I an air-cushion seemed at first likely to prevent its being used ; but a method of construction suggested itself, the expense of An Efficient 13lue Process Frame, for Printing from Large Negatives, or for Printing Simultaneously from many Small Ones. In order to be efficient, such a frame must be capable of keeping the sensitized paper everywhere tightly pressed against the negative. Again, such a frame, being large, is necessarily somewhat heavy. It should be so mounted that it can be I SECTION AT CO. handedwithcasei and,.inorderthat it.may printquickly,it top of the air-cushion, from sticking to the shellacked paper, should be arranged that it can be turned without delay at any The heat of the sun i‘ often sufficient to bring the shellac to a time, into a position that is square with the direction of the sun’s sticky state. It would probably answer as well to shellac the rays. , , ... , under side of the paper, and to use but one sheet, but I have not Undoubtedly, if a sufficiently thick plate of glass should be used, tried this plan. Around the periphery of the pad there is laid the ordinary photographic printing-frames would answer the pur- a piece of rubber gasket about, one and a-half inches wide, and pose, whatever the size ; but very thick plate glass is both heavy about one-eighth of an inch thick. In order that the gasket may and expensive. Commercial plate glass varies in thickness from not be too expensive, it is cut from two strips about three inches one-fourth to three-eighths of an inch and the thicker plates arc wide. One of them is as long as the outside length of the frame, rather rare. A large plate of it is easily broken by a slight uni- and the other is as long as the outside width of the frame. Each formly distributed pressure. But the pressure that is required for of these strips is cut into two L-shaped pieces, an inch and a-half the blue process printing, although slight, is much greater than is in width, with the shorter leg of each L three inches long. When used in the ordinary photographic process. For the sensitized the four pieces are put together, a scarf joint is made near each paper that is used in the blue process printing is, comparatively, corner, having an inch and one-half lap. It is somewhat difficult very thick and stiff, and it may cockle more or less ; while the to cut such a scarf joint as perfectly as one would wish, and it is paper that is used in ordinary photography is thin and does not best to use rubber cement at the joint. ~ cockle. Now, it is easy to see that a pressure severe enough to s - ■ - - - ■ •
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