MAKING READY ON CYLINDER PRESSES.
Make clean the bed of the press and the impression segment of the cylinder. Adjust the bearers a trifle above ordinary type height. See that the impression screws have an even bearing on the journals, and that the cylinder fairly meets the bearers. Select a suitable tympan or impression surface.
The tympan may be the India-rubber cloth which is furnished with the press, a thick woollen lapping cloth or blanket, several sheets of thick calendered printing paper, or one or more smooth and hard pasteboards. Each of these materials has merits not to be found in any other. Upon the proper selection of the tympan the presswork in great measure depends, and the pressman should be thus guided in making choice.
A pasteboard tympan is most suitable for wood-cuts, for perfectly new type, and for the best kinds of presswork. It is not suitable for miscellaneous work, nor for heavy forms, nor mixed old and new type. If the overlaying is properly executed, a pasteboard tympan will enable the pressman to show a sharper edge and a more delicate impression of the type than can be possible with any other, and it will wear the type less than any other. But it will require a very tedious and careful making ready, or it will prove very destructive to type.
A woollen blanket is best adapted for old stereotype plates, for very old type which has been rounded on the edges, for posters with large wood type, and for all common work which requires a clear but dull impression. For such work a woollen blanket will enable the pressman to make ready a form more quickly than with any other material; but it is injurious to new type, and incapable of producing a fine and sharp impression.
Thick paper is much used for book-work. It also answers well for script circulars and leaded forms. It will not answer so well for mixed old and new type, nor for table-work with unequal heights of brass rule, nor for mixed large and small type. It will prove most serviceable for the average of light and fine presswork.
The India-rubber cloth combines many good qualities not found in other tympans: it has something of the density of the pasteboard, the hardness and evenness of paper, and the flexibility of the blanket, combined with an elasticity peculiarly its own. It will compass a greater variety of work than any other: posters, script circulars, news and book forms, stereotype plates, and old or new type, can all be well printed with an India-rubber blanket. When it is intended to make one tympan answer for all kinds of work, the India-rubber blanket will be found decidedly superior to all others; but when very extra presswork is wanted, the tympan must be specially adapted to the form of type.
There are forms for which none of these tympans are specially suitable. For such cases careful pressmen combine two or more together,—as Welsh flannel over rubber, or thin rubber over pasteboard or under paper. These, however, are exceptional cases, and are only thus combined when very good presswork is wanted from imperfect materials. Careful observation of the quality of the impression given by each style of tympan will teach a pressman how to combine to the best advantage. As it requires experience and discrimination, an arbitrary rule cannot be given.
Whatever may be the material selected, the tympan must be stretched very tightly over the cylinder. All labour in overlaying is but thrown away if this is not carefully attended to. A rubber or woollen blanket can be secured at one end of the cylinder by small hooks projecting inward, while it may be laced tightly with saddler’s thread at the other end; or, by sewing on that end of the blanket a piece of canvas, it may be wound tightly around the reel, and kept secure by the pawl and ratchet.
But paper and pasteboard require a different process,-viz.: Take a piece of Nonpareil cherry reglet of the full length of the cylinder. Trim down the paper or pasteboard to the width of the bed between the bearers, but leave it a little longer than the impression segment of the cylinder. Then crease the pasteboard at a uniform distance of half an inch from the narrower end, and lay this creased part on the flat edge of the impression segment of the cylinder, under the grippers. Put the reglet over this, and bring down the clamps hard on the reglet, so as to bind all securely. When this is done, a thin web of muslin may be stretched over the whole, in the same way in which a blanket is laid on, and rolled up tightly, which will prevent any slipping of the board or of the overlays pasted on it.
A large poster, or newspaper form, or any large form with old type, will require a soft roller with much suction. Book-work, wood-cuts, or fine job-work, will require a harder roller, with very smooth, elastic, and clinging surface. Coloured inks are best printed with a still harder roller and with much less suction. All rollers should be perfectly clean, and free from cracks or holes. The suitableness of these rollers cannot well be explained by words: such a knowledge will be best acquired by observation and experience. It may, however, be necessary to state that one roller will not answer for all styles of presswork: the quality of the work, the size and wear of the type, and the speed of the press, must control the pressman in his choice.
Posters, with large wood type, require a semi-fluid ink, but not surcharged with oil. Ordinary news-work requires a better grade, more tachy, and finely ground. Good book-work should have a stiffer-bodied ink, soft, smooth, and with little oil. Job ink, which is made expressly for presswork on dry paper, should be used only for such work. Book and job inks are not convertible: an ink for wet paper will not work well on dry paper, and vice versâ. Very fine presswork—such as wood-cuts, or letter-press upon enamelled paper—calls for an ink impalpably fine, very stiff, of brilliant colour, and nearly or absolutely free from oil.
Every job-office should keep four grades of ink,—news, book, job, and wood-cut. They can be compounded (if no ink-manufacturer is near) with each other, or reduced with varnish to suit any form. Good presswork is impossible without good inks.
Charge the ink-fountain with the ink selected, and keep it well covered, to protect it from paper dust. Turn down the screws, and cut off all the ink evenly. When the form is ready, turn on the ink cautiously, and wait for ten or twelve impressions before again altering the screws. For small forms and short numbers of any piece of presswork in coloured ink or extra ink, a fountain is not necessary. The ink may be applied with a brayer or palette-knife.
The adjustment of the margin is the next process. Although type can be printed from any quarter of the bed, it will be found most judicious to lay all forms close to the back part of the bed, and equidistant between the bearers. This will secure a good impression, give a fair average margin to every form, and allow the full use of the bed for a large form, without resetting the cylinder. The bed and cylinder travel together, and the grippers, which bring down the sheet to the form, should barely lap over the back part of the bed. So long as the toothed cylinder wheel, and the short toothed rack on the side of the bed, remain undisturbed, the grippers will always pass over the bed in exactly the same place. When the grippers are in this position, (slightly lapping over the back of the bed,) take measurement of the distance between the back edge of the bed and the point of one of the nearest grippers. With a piece of reglet cut a gauge exactly corresponding to this measurement. Let no form be laid upon the press until the distance between the type and the edge of the chase tallies with the gauge. This will prevent the grippers from closing on the form and crushing the type. If the chase will not admit of so wide a margin, or if an extra margin is wanted on the sheet, put a piece of furniture of the extra width behind the chase: the margin can thus be increased or diminished at pleasure.
A book form may be locked up in a chase so large, with the type so far from the edge of the chase, that the grippers will bring down the sheet in such a position that it will be printed with the margin all on one side. To remedy this, the cylinder must be reset. Proceed thus. Remove the screw and washer, and draw the intermediate wheel out of gear, loosen screws in the gauge rack, then turn the cylinder to the point required, connect the intermediate wheel, adjust the gauge rack, and screw up tight.
The press having been adjusted, next examine the form to be printed. Not only see that it is gauged correctly, but also see that it is not locked up too tightly,—that chase, quoins, letter, and furniture are all level, and lie flat upon the bed. If the form springs, the quoins must be slackened; if this loosens the type too much, the justification should be amended. Make clean the type by rubbing it over with a dry brush. The rollers are often made foul and the colour of the ink changed by dust and particles of dirt clinging to the type.
Fasten the form so securely on the bed that it will not be moved by the action of the cylinder or the rollers. Take a proof on its own paper, using very little ink. Proceed to adjust the drop guides so as to bring the sheet exactly in the right position. Push out the iron tongues at the edge of the feed-board, and at equal distances from each other, so that they will equally sustain the paper. Slide the drop guides along the rod until they fall squarely over the tongues. Set the side guide so that it will give a true margin in length to the sheet to be printed. Adjust the grippers so that they will seize the sheet at proper intervals, making the margin exactly even by lengthening or shortening the drop guides. Then take a clean proof on its own paper, exactly in the right position, before making ready, when it may be shown to the reader. It frequently happens that an error in the margin, or an imperfection in the register, is thus noticed; and its timely discovery and correction before overlaying will save much time and trouble. A readable proof may be taken before overlaying, by running through a sheet or two of proof paper. Make register, if it is a book form, before underlaying.
When every thing has been found correct, then proceed to regulate the impression. If the type is fair, the proof should show a decently uniform impression; but if the form is large, or if it contains old and new or large and small type, then the proof will show an uneven impression. To rectify this inequality, pressmen use many expedients.
1. By lowering the bearers and putting on more impression. This, of itself, is a very poor way; for it wears down new type in order to show the face of the old, and invariably produces thick and coarse presswork.
2. By raising the low type to a proper height with thicknesses of paper under them, which is called underlaying.
3. By giving additional thickness to the tympan over every part of the form which shows a weak impression, which is called overlaying.
It is very rare that any one of these modes will prove sufficient: all should be used in conjunction. When the larger part of the proof-sheet shows a weak impression, almost approaching illegibility, then more impression should be added. When one side of the proof-sheet shows a weak impression, while that on the other side is full and clear, then more impression should be given to the paler side. The impression should be made decently uniform before any attempt at overlaying or underlaying. But the bearers should follow the impression screws, both being raised and lowered together, in order to secure the type from the unimpeded force of the impression cylinder. Not only should the bearers be of even height, but the cylinder shaft should always revolve on a true level. If the impression screws are carelessly used, and the bearers are rashly raised and lowered, this even bearing will soon be lost; the difficulty of obtaining a good impression will be much increased, and the press will receive a serious injury. For the same reason, the bearers should never be packed, (by the addition of cards, as is usual on a hand-press,) for it strains the cylinder and all its bearings with an irregular resistance. The bearers should be tampered with even less than the impression screws. When the impression screws are so set that the cylinder gives a fair uniform impression, they have done all that can be expected, and nothing more should be attempted by them. Sometimes the proof may show that a cut, or a line of type, or a set of brass rules, are higher than any other material in the form. But the impression should be set regardless of this: it will be found quicker and neater to reduce the impression on one or two such high lines, by cutting out the tympan-sheet over them, than it would be to underlay and bring up all other types to such an irregular height. Pitch the impression so that it will face the larger portion of the type, and make the less conform to the greater. Those parts which are high must be cut out of the tympan, and those which are low should be raised by underlays, and all inequalities regulated by overlays.
When any part of the form is very low, it will not answer to attempt facing it with overlays: it must be brought up to meet the inking rollers as well as the impression cylinder. When the proof shows low type, cut out the impression of it, raise the form, and paste it over the feet of the letter. If some types are high and some are low, make proper distinction, and carefully avoid increasing the height of any type or rule which seems to have a full impression. Pursue the same course when a marked depression appears in the centre, or a dwindling impression at the edges. Cut out that section which is light, and affix it to the defective part. If the impression dwindles in any part, the underlays must be cut of irregular thickness to suit the tapering off of the impression. Cut out an underlay from the edge where the impression begins to fade; then cut another of smaller size where it is utterly illegible; paste one over the other, laying them carefully in their proper positions, and then paste them all on the bottom of the form, where it is needed, taking care to lay the smallest underlay nearest the bed. This will restore the type to a proper level, and the next proof should show a uniform impression. The same plan will answer for a low corner. Use as little paste as possible, thin and free from lumps. Be careful that the underlays are laid on smoothly, without fold or wrinkle. Cut all underlays from a proof; for the proof serves as a guide both in cutting and in affixing to the form.
Underlaying should not be done to any great extent upon a cylinder press. It is a valuable means of bringing up an old line of type, a hollow, or a low corner. The underlays of any type form should not constitute more than one-fourth of the surface; if more than this is attempted, they will rarely ever fail to work up the quadrates and furniture. The action of the quickly moving cylinder upon a form of type underlaid with yielding paper, must create a spring and a rocking of all the materials in the chase.
Of all materials, old stereotype plates need underlays most, as they are usually very irregular in height. Thin card or pasteboard will be found preferable to paper for the underlaying of plates secured on wood bodies. When the plates are on patent blocks, always underlay between the plate and the block. Always cut the underlay for a plate less in size than the faint impression would seem to require. This will allow for the spring of the plate. If it is cut of full size, the next impression will disappoint the pressman, by being much harder at the edges than he intended. Never attempt to build up a type form to a proper impression entirely or chiefly by underlaying.
Underlays should be put under all large and bold-faced types when used with much smaller types, so as to raise them above the level of the others. This is needed to give it closer rolling, extra supply of ink, and that extra force of impression to transfer the ink to paper which all large types require.
When the type has been so levelled by underlays that all parts receive proper bearing from the inking rollers, and when the cylinder has a corresponding even impression, then overlaying may be commenced. For ordinary news, posters, or job-work, overlaying may be entirely unnecessary; the tapes and fly may be set, and the printing of the form may proceed without further delay. But fine press-work cannot be done without overlays. Underlays are chiefly valuable for securing an even impression; while overlays are indispensable for giving delicacy and finish to that impression.
To overlay a form properly, the tympan should be covered with a sheet of thin, smooth, and hard paper, stretched tightly. Then take a pale impression on the tympan-sheet, and also run through the press two or three proofs on thin and hard paper. Examine the proofs carefully on both face and back. If any brass rules or letters appear too high, cut them out of the tympan-sheet in one or two thicknesses, as their varying height may require. Go over the whole proof, examining every line carefully, and, by cutting out, reduce the impression of all projecting letters to a uniform standard. For this, as for all other work on overlays, use a very sharp knife with a thin point, and cut on a smooth surface, so that there will be no dragged or torn edge to the cut.
The next step should be to raise the impression of those parts of the form when the type appears dull or weak. Cut out carefully, and paste the overlays over the tympan smoothly. Overlays are worse than useless if they are not laid on firmly and smoothly, as the slightest bagginess will cause slur or mackle. If, by accident, the tympan-sheets or overlays should bag or wrinkle, tear them off, and commence anew.
Cut out and overlay the more prominent parts first; then try another impression, and from that cut new overlays for minor defects. Thus proceed until a perfectly smooth and even impression is obtained.
With common work it will be sufficient to cut overlays in masses, as pages or parts of pages; but with fine work every line and letter needs examination, and letters and parts of single letters are often overlaid by careful pressmen. When the pressman is expert at making ready, it is not necessary that he should take a new impression with every successive set of overlays. Many pressmen take a dozen proofs of a form on different styles of paper, and proceed to cut out and overlay on one of the proofs, and finally paste this proof on the tympan. But this boldness and precision can be acquired only by long practice. It is better for the young pressman to feel his way step by step.
The Impression.—A diversity of opinion exists among good printers as to the proper force of the impression: by some a heavy and solid indentation of the paper is considered necessary; while others insist that an impression which does not indent the paper is preferable. But the indentation of the paper is no test of the force of the impression. A light impression against a woollen blanket will show more forcibly than a strong impression against a paper or a pasteboard tympan.
Type is worn out not so much by the direct impression of the platen or cylinder on the flat face of a form, as by a grinding or rounding impression on the edges of the type, caused by the forcing of the tympan between the lines and around the corners of every letter. Every fount of worn-out type, whether from cylinder or platen press, has suffered less from a reduction in height than from a rounding of the edges. When the type is new and the tympan hard and smooth, the impression can be made so flat that the type will not round at the edges, and the impression will not show on the paper. But this cannot be done with old type or with a soft tympan: the impression must be regulated to suit the tympan. On fine work, a rounding impression should be avoided, as it not only destroys type, but also thickens the hair-line and wears off the ceriphs.
It is not sufficient that the paper should barely meet the type: there must be sufficient force in the impression to transfer the ink from type to paper. If there is not sufficient impression, it will be necessary to carry much ink on the rollers; and this produces two evils: the type is clogged with ink, and the form becomes foul; too much ink is transferred to the paper, which smears and sets off for want of force sufficient to impress it in the paper. Distinction must be made between a light and weak impression and a firm and even impression. The latter should be secured even if the paper is indented; though that is not always necessary. But a form of old type, a poster, or other solid form, must have a heavy impression, or else a very tedious and careful making-ready.
To set New Tapes.—Pass the tape around and close to the cylinder. Lap it over one of the tape pulleys, and then pass it around the small guide pulley on the shaft above. To increase its tightness, throw up the guide pulley from the shaft, and set the binding screw more tightly. All these pulleys are movable on their shafts, and distance between them may be altered at pleasure. Let the tapes rest upon the outer margin of the sheet, and see that the overlays on the tympan over which the tapes pass are of equal thickness; if not of equal thickness, the sheet will wrinkle.
To set the Fly.—Run through a sheet of the paper to be printed, and let it run down the fly so far that it is barely held by the fly pulleys. Then set the cam which works the fly, so that its point just clears the small friction roller on the shaft, and it will throw down the sheet correctly. Tighten the spring according to the size of the sheet, and set the spring crank so that it will prevent the fly from striking too hard on the table.
It will be seen that good presswork does not depend entirely upon the press, nor yet upon the workman or the materials. Nor will a superiority in any one point compensate for a deficiency in another: the newest type will suffer from a poor roller, and the most careful making-ready will be of no avail if poor ink is used. It is necessary that all the materials should be of the best kind,—that they should be well adapted to each other, and fitly used. Although a good workman can do much with insufficient materials, there are cases where a neglect to comply with one condition is equal to a neglect of all.[19]