PAPER MAKING MACHINERY.
Cheap literature and the large development of newspapers are principally attributable to the improvements in Paper Making, by the aid of machinery.
In the former modes of making paper, the workman held in his hands a square frame covered with wires, which he dipped into the prepared cotton or linen pulp, which was kept in suspension by being agitated in water, and taking up a quantity sufficient to cover the frame, he moved the pulp about horizontally, to spread it evenly over the surface of the wires. Another workman transferred the layer of pulp on to felt, and in this manner one sheet was laid upon another, with felt between each. They were next subjected to great pressure, for the purpose of making the fibrous particles cohere sufficiently to form sheets of paper. The felts were then removed, and the sheets were piled upon one another and again pressed, after which they were dried, sized, and finished.
Paper Making, by that process, was a slow operation. The thickness and evenness of the sheets depended altogether on the judgment and skill of the workman, and their size was necessarily limited by the dimensions of the frame. By the improved methods, nearly all the work is done by machinery. The soft fibrous pulp, which is to be converted into paper, enters the machine at one end, and in the course of two minutes it is delivered at the other end of the machine in a continuous sheet, that may extend for miles. By supplemental contrivances the paper is cut into sheets, piled together, and presented in a salable form.
The world is indebted to a Frenchman, named Louis Robert, for the invention of the first machine for making paper. He was a workman in M. Didot's paper mill, at Essones, and for his contrivance of a method for making continuous paper, he obtained from the French Government, in 1799, the sum of 8,000 francs and a patent for the manufacture of the machines. The political agitation in France at that period prevented much progress from being made with the invention, but after the Peace of Amiens, in 1802, M. Didot, jun. came to this country, accompanied by his brother-in-law, Mr. Gamble, for the purpose of making arrangements to carry it into effect. They induced Messrs. H. and S. Fourdrinier to engage with them in bringing the machinery to perfection, and patents obtained in this country by Mr. Gamble were assigned to them in 1804.
The engineering establishment of Mr. Hall, at Dartford, in Kent, was selected as best adapted for the purpose of making the machinery and for carrying the plans into operation. Mr. Bryan Donkin, who was engaged in the manufactory, principally assisted in bringing the machinery to perfection. The difficulties attending the completion of all the parts, to get them to work effectually, and the obstruction encountered in introducing the machine-made paper, rendered the enterprise a ruinous speculation to those who first engaged in it. Messrs. Fourdrinier having expended £60,000 in perfecting the machine.
The apparatus, of which a representation is given in the annexed woodcut, was very complicated, but the essential parts may be readily understood.
The rags from which the paper is made undergo a variety of processes before they are properly reduced into a state of pulp. They are sorted, dusted, boiled, and torn into pieces by passing through cutting rollers; they are then bleached and again submitted to the grinding action of rollers, which reduce them into a state of fine pulp, resembling milk in appearance. The pulp thus prepared is placed in a large vat, where it is kept constantly agitated, to prevent the more solid parts from being deposited. From the vat the pulp is discharged into a cistern, over the edge of which it flows in a continuous stream upon an endless wire cloth, the meshes of which are so fine that there are as many as 6,000 holes in a square inch.
The wire gauze, on to which the pulp is poured, is about 4 feet wide, and 25 feet long, and it is kept constantly moving onwards, by rollers at each end, over which it passes. The gauze is stretched out perfectly level, and the pulp is prevented from flowing over the edges by straps on each side, which limit the width of the paper. As the endless wire cloth moves along, an agitating motion is given to it, by which means the pulp is spread evenly over the surface; the water is also drained off through the interstices of the gauze, and this part of the process is expedited in the improved machines by producing a partial vacuum underneath. Before the sheet of pulp has arrived at the farther extremity of the wire cloth, it passes between two cylinders, the under one of which is of metal, covered with felt, and the upper one of wood. A slight pressure given to the pulp in passing between those cylinders imparts sufficient tenacity to it to enable it to be transferred from the wire gauze on to an endless web of felt, by means of a slice that clears the pulp from the wire gauze, and deposits it on the felt. The latter is kept moving at exactly the same speed as the wire gauze, otherwise there would be either a rent or a fold on the sheet. The paper, still in a very wet state, is carried between cast iron rollers, and its fibres are forcibly pressed together, which operation squeezes out the water, and so far gives tenacity to the pulp that it may be handled without tearing. The sheet then passes on to other rollers, by which it is further compressed, and its surface smoothened. The paper is, however, still damp, and requires to be dried. This is done by passing it over large metal cylinders, heated by steam. The process of making the paper is then completed, and the continuous sheet may be wound upon a reel to any length; but it is now usual to cut it up into sheets as soon as it leaves the drying cylinders.
The wire cloth moves at the rate of from 25 to 40 feet per minute, and such a machine would consequently make at least 10 yards of paper in that time, which is equal to a mile in three hours. The width of the paper is usually about 4½ feet, therefore each machine will make 10,450 square yards of paper in twelve hours; and there are upwards of three hundred of such machines at work in this country. The value of the paper thus produced is calculated to exceed two millions sterling.
Numerous improvements have been made in Fourdrinier's original machine, but the principle of its construction remains essentially the same, and it is by this means that most of the paper now used for writing or printing is manufactured. A paper-making machine, on a different principle, has, however, been invented by Mr. Dickinson, and has been carried by him to great perfection. Instead of allowing the pulp to fall on to a flat surface of wire gauze, a polished hollow brass cylinder, perforated with holes and covered with wire cloth, revolves in contact with the prepared pulp, and a partial vacuum being produced within the cylinder, the pulp adheres to the gauze, and its fibres cohere sufficiently, before the cylinder has completed a revolution, to be turned off on to another cylinder covered with felt, on which it is subjected to pressure by rollers, and is thence delivered to the drying cylinders.
Mr. Dickinson afterwards obtained a patent, in 1855, for making a union paper, consisting of a thin sheet of that made by his own machine, and a similar sheet made by a Fourdrinier machine united together. For this purpose the two sheets were brought together, as they passed from the machines, whilst still wet and in an unfinished state, and were pressed together between rollers, by which means they were completely incorporated. The object of this contrivance was to combine, in a single sheet, the different kinds of surface which paper made by those two modes of manufacture present. It is also employed economically for engravings, to give a fine surface to a thick sheet of coarser material. The threads in postage envelopes and in bankers' cheques, are introduced by this process of plating two surfaces together.
The greatly increased consumption of paper threatened to exhaust the supply of the raw material, notwithstanding the large import from abroad and the enormous supply derived from the waste of the cotton mills, which, when mixed with rags, produces good paper. The quantity of old rags, old junk, and other fibrous materials imported for the purpose of making paper, in 1850, is stated in the Jury Reports of the Great Exhibition to have amounted to 8,124 tons. This large importation, added to the stock of rags supplied by the country itself, was, however, inadequate to meet the consumption, and search was anxiously made for other fibrous substances that could be converted into paper;—peat, cocoa-nut fibre, grass, straw, and even wood have been used for the purpose. Of those substances, straw has been most successfully applied, and straw paper—excellent to write upon, though not bright in colour—is now made at very low prices. The straw is first cut up into short lengths, of about half an inch, by a chaff-cutting machine, and after undergoing various processes of trituration and bleaching, it is reduced into a pulp, sufficiently adhesive to make a strong paper.
The plan of drying the paper as it leaves the rollers of the machine, was introduced by Mr. Crompton in 1820, and that gentleman was also the first to introduce a machine for cutting the paper into sheets as soon as it is dried. The first invention of the kind was patented by Mr. Crompton, in conjunction with Mr. Miller and Professor Cowper, in 1828. The continuous web of paper was made to pass directly from the drying apparatus to the cutting machine, by which it was first slit into bands of the required width by means of a series of sharp discs of steel, adjustable on two parallel axes. The bands of paper then passed on to shears, placed transversely, that cut it into sheets of any required length, which were laid upon one another, to be divided into quires.
Several other cutting machines have since been invented, the simplest of which is the one patented by Mr. Dickinson, which is represented in the woodcut.
The paper may be taken directly from the drying cylinders or from a reel, as shown in the diagram at a. The sheet passes over a large drum and through several guide rollers, till it is carried across the table a h, where it is cut lengthwise by knives, as it passes along. A series of chisel-edged cutters are placed at regulated distances beneath the table; and whilst the paper is stretched over it, several circular knives, f f, fixed into a swing frame, g g, at corresponding distances with the knives beneath, are swung across the sheet, and cut it in the manner of a pair of shears. Other kinds of cutting machines are contrived, by which sheets of writing paper, when collected in quires, are squeezed tightly together, and their edges are smoothly and evenly cut.
We must not conclude this notice of Paper Making Machinery without alluding to the ingenious self-acting mechanisms for making envelopes. In the Great Exhibition of 1851 there were three different machines exhibited in action, each one producing, with great rapidity, those neat coverings for letters, for which the penny postage system has created so great a demand. The paper, cut into the desired form by a separate machine, was piled up on one side of the envelope folder. It was taken, sheet by sheet, and stretched on a small table, on the middle of which there was a trap door, held up by a spring to a level with the rest of the table. A plunger, of the same size as the envelope to be made, pressed the trap down into a recess, and raised the four corners of the paper, the edges of which were then gummed, and small mechanical fingers folded them down. The completed envelope was then thrown out into a basket, or it slided out of the machine on to those before made.
Each of those machines, with a boy as an attendant, will fold 2,700 envelopes in an hour, which is nearly the same number that an experienced workman can fold in a day with a folding stick. Notwithstanding the supplanting of manual labour to so great an extent by these ingenious mechanisms, the effect of increased facility of manufacture has been to give increased employment, and many more persons are now engaged in making envelopes than were so employed before the invention of the machines.