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It may be well to make note here of the extraordinary precautions that are taken to insure against loss of any of the printed or unprinted paper.
The printing department is charged for a certain number of full sheets of paper when the day's work begins. When the day’s work is over, the finished sheets must be counted and every scrap of paper m'ust be accounted for, whether it be in the form of perfect large sheets of stamps or press waste. A voluminous and very detailed report must be made if so much as one scrap of the paper cannot be found. Great care is taken to prevent these inconvences and it is rarely necessary to make such reports. _
The finished sheets are, of course, imperforate and ungummed. They are delivered to the store room in counted packages, to facilitate accounting further along the line when they are delivered to the gumming d'ivision.
The Gumming Division
ALL stamps which are printed on the
fiat bed presses pass through the gumming division, where they are gummed and prepared for perforation. As we enter the division we pass a room on our right which reminds us a great deal of a soup There are several large steam heated kettles along the walls of the room where the ingredients for making the gum are dissolved and mixed. Near the door is an electrically operated pump by means of which the prepared gum is delivered to the various gumming machines.
Two varieties of gum are made. That for the sheets printed on the fiat bed presses is for the most part a solution of dextrin to which is added about 3 per cent of glucose. The latter ingredient is added so that the film will hold a certain amount of moisture and prevent the paper from curling. The gum which is made for the stamps from the rotary presses contains from 10 to I2 per cent glucose, since the paper is slightly heavier and receives no working. A great deal of moisture must
therefore be retained in the latter paper to prevent curling.
The ungummed sheets of stamps from the flat bed presses are fed with the printed side down to the gumming machines, in much the same manner that single sheets of paper are fed to the old type cylinder printing presses. They pass under a roller which carries the gum solution to the sheet and, as they emerge from this, mechanical grippers on endless belts catch hold'of each margin of the sheet. These endless chains carry the sheets through a long drying box where the gum is quickly dried. They emerge from the end of the chamber and are released by the grippers automatically. An arm picks them up, turns them over and piles them neatly on a shelf at the end of the machine.
Here we see a very interesting operation. Girl operators pick about fifty sheets at a time from the shelves, inspect them for imperfections and then bend, roll and twist them in all directions in order to make the paper pliable. The paper is so well worked in this manner that sheets, even after being perforated, will lie flat on the table without curling. It is this strenuous working of the paper which makes it possible to use so little glucose in the gumming of these stamps.
Imperfect sheets are all separated and, if torn, are pasted on large sheets of paper to facilitate accounting. Every stamp must be accounted for before the perfect sheets are passed on to the perforating and finishing division for the final operations.
Perforating and Finishing IN the perforating division the sheets of 400 subjects and the booklet-sheets are handled in different manners. The 400subject sheets are perforated and cut into post office panes of I00 subjects each, while the booklet sheets of 360 subjects are perforated and are sent to the booklet division for finishing. The 400-subject sheet has the usual margins on all sides, two plate numbers on each side opposite the fifth stamp from the cor
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ner, and the usual guide lines, one hori-
When the sheet is passed lengthwise through the perforating machine the sides are trimmed fairly close to the edges of the stamps. Perforations are received between the first and second, the third and fourth, vertical rows, etc. The space between the second and third, the fourth and fifth, vertical rows, and so on is left imperforate. When the sheet is passed sidewise through the machine the bottom of the sheet is trimmed close to the edges of the stamps and sufficient margin is left at the top for binding. Perforations are given above each row of stamps but not below the bottom row of each group of three. These sheets, so perforated, are passed on to the booklet division for finishing.
Manufacture of Booklets S EVERAL different types of booklets are made for the post offices. These booklets are laid out a sheet at a time, first the bottom cardboard, then a sheet of paraffined paper, then the required number of sheets to conform with the denomination desired, each interleafed of course with paraffined paper, and finally the cardboard cover stating the price of the booklet. The staples are then put into the binding margins and the whole is cut into six horizontal rows of booklets. Each row is then cut into ten individual booklets, which are counted and packed for shipment to the postmasters. It is to be noted that the parts of the booklet sheets which were left imperforate by the perforating machine have coincided with the edges of the small booklet.
Operation of the Rotary Press
HE improvements which have been made in the mechanical affixing of postage stamps to mail, and the development of stamp-vending machines, are primarily responsible for the decision in favor of the machine-printed stamps. There has been agitation in some quarters in favor of machine-printed stamps for almost thirty-five years, due to the lower cost of production and the greater output which could be realized. In 1910 work was begun on the development of the new rotary press, due to the rapidly increasing demand for coil stamps. What is now known as the small rotary press was installed and ready for opera
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tion early in 1914 and the first stamps from this machine were issued by the Post Office Department on June 30, 1914. The Bureau now has six small rotary presses and four large ones in operation.
At the time the rotary press was installed, coils were being make by cutting the imperforate sheets into strips of twenty subjects and attaching them end to end until the coil contained the required 500 or 1000. 'Twenty-four pasting operations were necessary for a coil of 500 stamps and forty-nine were necessary in making a coil of 1000 stamps.
‘The rotary press was designed to print a continuous sheet of stamps for use in coils. The paper is fed to the machine at one end, is moistened at one side, and receives its impression from the inked plate. It then passes over electricallyheated rolls to dry the paper a11d ink. The back of the sheet is gummed, passes into the long drying box and emerges from the oven at the end of the machine, where it is rolled up on a large roll. The production is continuous, all of the above operations being performed by the one machine.
Two semi-cylindrical printing plates are necessary and they are so carefully fitted to the cylinder of the press that only a very faint line shows at their junction. The plates for the sidewise coils make an impression I0 subjects high by I7 subjects wide and the plates for the endwise coils make an impression I5 subjects high and 10 subjects wide. The plates are inked and wiped in exactly the same manner as the fiat plates, the same coarsely woven cloth being used. The strip of paper is fed into the machine so that the impression from the ink plates faces down as the gum is applied. The application of the gum is accomplished in the same manner as previously described.
One revolution of the sidewise coil plates will of course print 340 stamps, a pane of I70 for each plate. A vertical line appears between each of these panes. This is due to the fact that the ink is taken up by each of the crevices at the junction of the plates. It will be noticed that this line varies in thickness, depending on whether the edges of the plates fit accurately.
The small presses will each print about 2,500,000 of stamps each working day of eight hours. The large presses will each produce from 8,000 to 10,000 sheets of 400 subjects, or from 3,200,000 to 4,000,000 stamps each day.
The product from the rotary presses can easily be distinguished from stamps printed from the flat plates.
The rotary stamps have a softer, more uniform appearance, and each line of the engraving stands out more clearly and distinctly. Aside from their appearance, which is suflicient to distinguish them to one who is familiar with their appearance, it is well known that they are larger than the stamps printed on the flat plate presses. This may be attributed partly to the difference in the shrinkage of the paper which is used for these stamps, but principally to the surface-change in the plates as they are bent to fit the cylinder.
Perforation of Rotary Stamps
HEN we see the machine which per
forates the roll of rotary stamps we wonder how the Bureau is able to control the position of the perforation as well as it does.
It is a much more difficult task than it appears to be. Perforating wheels can not be used on this machine, since all coil stamps have to be perforated at right angles to the length of the sheet. It is necessary, therefore, to punch a row at a time and this is accomplished by a revolving roll fitted with several rows of perforating pins.
The sheet passes through the machine at so high a speed that it would be impossible to observe whether the perforations are being accurately placed, were it not for a clever little device which is based upon the same principle as our motion pictures.
An instantaneous ray of light is made to shine through the sheet simultaneously with the punching of each row of holes. This occurs several times each second, and the eye of the operator receives these light impressions much in the same way as we receive the impression of each of the individual pictures thrown on the motion picture screen.
Although the sheet is moving rapidly, the image of the stamp through which the light shines appears to remain stationery or to