Part 10

Second. From the sand settlers the stock runs on to a screen, through which it is drawn by means of suction. This process prevents fibres which are lumpy and too long from getting on to the machine, and allows only those of a certain size and length to go forward to be made into paper. An endless and very fine wire cloth, which is continually moving at the same rate of speed as the rest of the paper machine, takes the stock after it has been screened. This is the first step toward making the material into actual paper. Thick rubber straps on each side of the wire determine the width of the paper. This wire shakes a little in order to weave the fibres together while in a state of suspension. At this period the stock looks like thick cream, but soon changes its appearance to the form of a sheet more or less solid on coming to the end of the wire, where there is what is called a "dandy,"--a roll covered with similar wire cloth pressing lightly on the paper as it runs along the wire. Designs in relief on the surface of this roll produce the well-known marks called "water marks." Just beyond the "dandy," underneath the wire, is a suction box which draws enough of the water out so that the paper can go through the "couch" roll at the end of the wire without being crumbled.

Third. The couch roll is a small hard roll covered with a thick felt called a "jacket," and is used on the paper machine to prevent the paper from being crushed, for it presses out much of the water and flattens the paper so that it will pass from the wire to the felts without breaking and through the press rolls without crushing. From this couch roll the paper leaves the wire and is carried along on an endless woollen felt to the press rolls, which are made of hard rubber, steel, or brass. These rolls press the fibres together well, squeezing out more of the water and flattening the sheet.

Fourth. From the press felts the paper is carried to the "dryer felts," which in turn carry the paper to the "dryers," which revolve and by means of the felt carry the paper along to the next dryer, and so on. The dryers are hollow iron or steel cylinders, heated by means of the exhaust steam from the engines which run the machine. More or less steam is allowed to run into the dryers, according to the quality of paper being made.

Fifth. As soon as the paper has been carried over all the dryers, during which time it becomes, perfectly dry, it is run through a set of so-called steel "chilled rolls," at the end of the machine, which are under pressure and which give the paper a fairly smooth surface for ordinary type printing. If a rough surface is desired, the paper is simply wound on reels from the dryers.

Super-calendered papers are those which have a high finish and smooth surface, and are used for cuts, lithographic work, magazine papers, and ordinary illustrations. To calender paper, it is run through a series of alternate "chilled" and "paper" rolls. The chilled rolls are made of steel and have a very smooth and even surface. The "paper" roll is made of circular discs of thin, but strong manila paper, clamped together on an iron shaft, and then put under hydraulic pressure, this pressure being increased constantly until it reaches one hundred tons of pressure to the inch. The rolls are sometimes kept under this pressure for five or six weeks, and then are turned on a lathe into a true and smooth cylinder, and finally burnished by being revolved against each other.

A "cotton" roll, used at times in place of the "paper" roll, is made in the same manner, except it is made of pieces of cotton cloth instead of thin manila paper. There is a heavy pressure on these rolls, and the paper goes through at a high rate of speed. When an especially smooth surface is wanted, steam is run on the paper as it unwinds, dampening it and giving the web a surface like that on ironed linen.

"Coated" paper is treated differently, being covered with a fine coating, which, after super-calendering, gives the paper a glazed and smooth surface for fine half-tone illustrations. Clay, mixed with casein, the product of skimmed milk, or glue, is the chief material used for coating. It is put on the paper by means of large brushes. Then it is dried by fans and passed through a long passageway heated by steam to a high temperature. After being reeled, it is allowed to stand for a while to harden; then is run several times through the calenders to get the smooth surface. If a high, glazed finish is necessary, steam is put on while running through the calenders. This gives a very bright surface for fine lithographic work. For the best coated papers, instead of clay, sulphate of lime and sometimes sulphate of barium is used, with glue or casein. Formaldehyde, a chemical compound, is used to prevent decomposition in the coating materials; and soda or borax is used to "cut" or dissolve the casein or glue.

If the paper is to be printed "from the web," that is, from the roll, it first has to be trimmed to the correct width, then wound tightly under a high pressure to a certain thickness, then the rolls are packed up in wrapping paper ready to be shipped. Some rolls contain as much as five miles of paper. When the paper is to be put up in sheets, it has to be cut to exactly the correct width and length on the cutting machine. It is all very carefully sorted--the imperfect sheets being thrown out--counted and packed in wooden cases, or done up with strong wrapping paper in bundles, ready to be sent to the printer.

PRESSWORK

By Walter J. Berwick.

Books are printed in "forms," or sheets, of four, eight, twelve, twenty-four, or thirty-two pages at a time, the number being determined to a great extent by the size of the type page and by the class of the work.

An ordinary twelvemo book, without illustrations in the text, is usually printed in forms of thirty-two pages, on what is known as a single-cylinder flat-bed press, which prints only one side of the paper at an impression. For large editions, the size of the sheet of paper is sometimes doubled and sixty-four pages printed at a time. The class of work in question may also be printed on perfecting presses which print both sides of the paper at one time, and in this way as many as one hundred and twenty-eight pages are frequently printed on one sheet, there being sixty-four pages on each side. Large editions of books having small pages, such as small Bibles, are often printed two hundred and fifty-six pages (one hundred and twenty-eight on each side) at one time.

High grade, illustrated books are always printed on one side of the sheet at a time, the reverse side being printed after the first impression has dried properly. Thus a smooch, or "offset," the result of handling the paper before the ink has become dry, is prevented.

For convenience, I shall describe the process of printing a book from electrotype plates on a press which prints thirty-two pages at a time and on only one side of the paper.

Before ordering his paper, the publisher must first determine the size of the paper page of his proposed book, and from this arrive at the necessary size of the sheets of paper. He must also determine the thickness of the paper needed to give the finished book its proper bulk.

If the book is to be trimmed on top, bottom, and front, about one-eighth of an inch must be allowed on top and front for the binder to trim off, and about one-fourth of an inch on the bottom. The dimensions from back to front, including the amount left for the "trim," should be multiplied by eight; and the page dimension the other way, including the trim, by four. This would give the size of paper needed. As an illustration, if the trimmed size of a book is 7-7/8 x 5-3/8 inches, the paper should be 32 x 44 inches. If the book is printed 16 pages at a time, the paper should be 22 x 44; and if 64 pages at a time, 44 x 64.

The quality of the paper and the size of the sheet being decided upon, and the number of pages known, any large paper house can tell the weight necessary to give the required thickness to the book.

On receipt of the printing order, with directions as to whether the book is to be trimmed or not, the printer first makes up what is called a "form" of so-called "patent" blocks on which the stereotype or electrotype plates are placed during the printing of the book. These blocks are made of wood or iron planed to an even thickness of about three-fourths of an inch, so that when an electrotype plate is placed upon one, it will take only a few thicknesses of thin paper between it and the electrotyped page to make the whole "type-high," that is, as high as an ordinary piece of type.

Two adjacent edges of these blocks are bound with strips of brass, which project above the block and are turned over slightly, so as to receive the two bevelled edges of the electrotype plate. The other two edges are provided with movable clamps, which are screwed tight against the flat edges of the electrotype plate by means of ratchets, thus holding the plate firmly in its place.

In practice, the longer of the two brass-bound edges is called the "back" of the block and the shorter one the "head," the other long edge being known as the "front" and the other short edge, the "foot." These terms, as a matter of fact, originated from the use of the same words in describing the printed page of a book, the "back" corresponding with the side of the page next to the binding of the book, the "head" being the top of the book, and so on.

One-half of a set of blocks--thirty-two being a set in this case--are made with the backs on the left and one-half with the backs on the right edge of the block. The common way is to place thirty-two of these blocks, in four rows of eight blocks each, in a "chase," or iron frame, with a cross-bar in the centre. Thus sixteen blocks are on each side of the cross-bar, and all have their backs toward it. The form then appears like this:--

Strips of wood, called "furniture," are then used to fill up the spaces between the blocks, care being taken to see that all the backs, fronts, and heads are in uniform positions. As some people prefer the printed pages of a book to be near the centre of the paper pages, while others like the head and back margins to be much narrower than the margins at the front and foot, the distances between the blocks must be arranged according to the taste of the publisher or the author.

After the blocks have been spaced as desired, and the spaces filled with furniture, the form is "locked up," or tightened securely, with wedge-shaped pieces of iron called "quoins," and it is then placed in position on the bed of the press, securely fastened by screw clamps, and "making ready" for printing is begun.

Notwithstanding the care that has been taken to have all the "patent" blocks and the electrotype plates of even and uniform thickness, there is almost never a case where a form can be put on the press and printed off properly without considerable work being required to make the surface of the plates absolutely flat so that the entire printed part of the page will receive the same amount of ink and will press evenly on the paper.

The first step in making a press "ready" is to place a sheet of heavy cardboard around the cylinder, and over it draw a smooth piece of muslin or cotton cloth. This is called the "packing." In many of the best offices this sheet of heavy cardboard is not used, but in its place is a patent make-ready called "Tympalyn."

Over this a thick sheet of manila paper is shrunk, it being pasted under clamps on the front of the cylinder, and carried around and fastened to hooks on a rod on the back. The rod is then turned until the sheet is perfectly tight and smooth.

While the pressman is laying out his plates the feeder should be cutting thin sheets of paper the size of one of the plates. Some of these papers are cut about one inch shorter than the plates for "bevels," and these are pasted on the middle of the full-size pieces. These bevels and the larger "blank" sheets are to go between the plates and the blocks to overcome any variation there may be in the thickness and to make the surface of the form as nearly level as possible. The "bevels" raise the centres very slightly above the edges of the plate, thus reducing the pressure of the cylinder at the points of contact and departure, and saving the plates from wear.

The cylinder being properly packed, and the form of blocks fastened on the press so that the impression of the form will come in the middle of the paper sheets, it is necessary to know whether the binder is to fold the sheets by hand or by machine, and if the latter, what kind of machine, as different ones require different "imposition" or arrangement of pages. This being decided, the plates are fastened on the blocks so arranged that when the sheet is cut and folded the pages of the book will run consecutively. Before levelling up the form with the bevels and blank sheets, the plates of all open or short pages, if any, are replaced with solid pages, as these sheets and underlay are to remain through the printing of all the forms of the book. The rollers are now put in the press and adjusted to just touch the inking table, the ink put on the rollers and distributed, and one impression printed on one of several sheets of thin paper which are run through the press together. This printed sheet is then turned face down by the pressman and any unevenness of the impression noted. One of the printed pages is taken as a standard and by removing as many pieces of the thin sheets as necessary from under the plates where the impression is too heavy, and by adding where it is not heavy enough, the surface of the form is finally "evened," or made as nearly equal as possible.