For a bellows for a half-plate camera we require a piece of leather or paper 26 in. by 22 in. We next proceed to mark it on the inside surface by drawing a number of lines A in. apart lengthwise. (See Fig. 64.) Then four lines across at distances of 4A 5, 7, 5, and 4 j4 in. respectively, representing the four corners. On either side of these four lines rule, at a distance of A in., dotted lines as a guide for the interlacing diagonal lines, as shown in the accompanying illustration. The spaces marked A B C represent the bottom sides and top respectively, the bottom side being divided, and an allowance made for the lap.
First fold all the 7 lines backward and forward until the whole has the appearance of a fan.
Care should be taken that every fold is neatly and carefully made, . _ _ otherwise your bellows when completed will assume a very unsightly appearance. Place, when folded, between the jaws of a carpenter's bench, and screw up tightly, If a carpenter's bench is not handy, apply pressure by any other means you can think of. When this is done lay it out fiat, and fold it across the four lines, they being inside. The laps are then glued together by securing one end of a long, flat piece of wood in a vise, and then sliding the bellows over it, allowing the lap to rest over the wood. Glue together, and a slight pressure will secure a permanent light tight joint. If the laps when placed together form too thick a joint, it is as well to thin them with a sharp penknife.
When the joint is perfectly dry, we have to form the bellows. This is accomplished by folding the diagonal lines inside in such a manner that the outer surfaces touch each other, con tinuing the manipulation of each corner of each separate fold singly ; as the folds are made they should be well rubbed down , with a piece of smooth wood or bone handle in order to give a sharp and permanent edge. If the previous operations have been carefully undertaken, it will be quite surprising to the operator to find how easily these folds can be made to harmonize.
The inside of the bellows should then be coated with a dead black, composed of either lampblack, French polish, or shellac, dissolved in water by the addition of borax or ammonia, and lampblack added thereto.
The form of bellows already described is a plain one—that is to say, the front and back are of the same size. The following is a description of the method of making a conical bellows*: Fig. 65 gives the plan of laying out the lines for the folds. It is similar to the first except that special compensation has to be made for the gradual tapering of the bellows, the width of one half of the folds being proportionately narrower than the other half. The size given is for a io x 8 camera. The size of the sheet of leather or paper required is 38 x 24 inches. In the accompanying
drawing the single black lines represent the lines to be folded on the outside and the double lines for the inside folds. Securing our material we cut it to the size required, i.e., 24 x 38 inches, and first draw a centre line in the direction of the length of the bellows.
Then our bellows is to measure io34 inches at the back and 6g inches in the front. We cal culate half this measurement on either side of the centre line, and then connect the ends of the two front and back cross lines, the oblique lines form ing the two upper radical corner lines of the bellows. The sides are to measure'8g inches at the back and 4 inches at the front. We again divide the distance at each end, and locate the side centre lines. From these we can easily determine the location by measurement of the two lower radial corner lines of the bellows. The bottom of the bellows is then divided, and one-half added to each side of the sides of the bellows, an extra half-an-inch being allowed for the lap or joint. The crease lines for the folds are next determined by first dividing off on the respective centre lines, in equal distances, the width of a double fold, which may be about inches. The measurement should commence from the wide end, and proceed toward the small end. Cross fold lines are then drawn between the four radial corner lines in each section at right angles to their respective centre lines, and will meet each other, producing a shape similar to a portion of octagon. The next step is to locate the position of the intermediate fold. This is done by laying the base of a draughtsman's triangle on the base line or back line, and drawing a line at 45 degrees inward from the intersection of the corner line with the back line nearly across the fold, then by reversing the position of the triangle, so that its base is coincident with the next fold line, and drawing another diagonal line at 45 degrees inward from the intersection of the fold line with the radial corner line to where it will cross the other diagonal line. Where they meet will be the proper location of the intermediate fold line. This will be the same for all the intermediate folds. The points for these should then be located on the centre line, and they should be drawn parallel with the other fold lines between the two centre corner lines. Each side of the bellows is measured off in this manner, the corner folds being located by drawing lines three-quarters of an inch distant from the corner lines parallel with the latter, and crossing the squares so formed by diagonal lines which represent the zigzag lines of the corner folds. In finding out the position of these various lines, dividers or any pointed instrument must not be used, as it is likely to make small holes in the material.