Paper & paper making, ancient and modern

by Richard Herring

With respect to hand-made papers, the sheet is formed by the vatman’s dipping a mould of fine wire-cloth fixed upon a wooden frame, and having what is termed a deckle, to determine the size of the sheet, into a quantity of pulp which has been previously mixed with water to a requisite consistency; when after gently shaking it to and fro in a horizontal position, the fibres become so connected as to form one uniform fabric, while the water drains away. The deckle is then removed from the mould, and the sheet of paper turned off upon a felt, in a pile with many others, a felt intervening between each sheet, and the whole subjected to great pressure, in order to displace the superfluous water; when after being dried and pressed without the felts, the sheets are dipped into a tub of fine animal size, the superfluity of which is again forced out by another pressing; each sheet after being finally dried, undergoing careful examination before it is finished.

Specimens 2, 3, 4, and 5, inserted at the end of the work, serve to illustrate the different stages of the manufacture. First, we have what is termed the water-leaf, (2) or the condition in which the paper appears after being pressed between the felts—this is the first stage. Next, a sheet from the bulk, as pressed without the felts (3) which still remains in a state unfit for writing on, not having been sized—and is in fact but white blotting paper. Then we have a sheet after sizing, which completely changes its character (4); and lastly one with the beautiful surface, which most of us, in this steel-pen age are capable of appreciating (5). This is produced by placing the sheets separately between very smooth copper plates, and then passing them through rollers, which impart a pressure of from 20 to 30 tons. After only three or four such pressures, it is simply called rolled (5), but if passed through more frequently, the paper acquires a higher surface, and is then called glazed (6).

The paper-making machine ([see frontispiece]) is constructed to imitate in a great measure, and in some respects to improve, the processes used in making paper by hand; but its chief advantages are the increased rapidity with which it accomplishes the manufacture, and the means of producing paper of any size which can practically be required.

By the agency of this admirable contrivance, which is so adjusted as to produce the intended effect with unerring precision, a process, which in the old system of paper-making, occupied about three weeks, is now performed in as many minutes.

The paper-making machine is supplied from the “chest” or reservoir (F), into which the pulp descends from the beating engine, when sufficiently ground; being kept in constant motion, as it descends, by means of the agitator (G), in order that it shall not settle. From this reservoir the pulp is again conveyed by a pipe into what is technically termed the “lifter” (H), which consists of a cast-iron wheel, enclosed in a wooden case, and having a number of buckets affixed to its circumference. The trough (I), placed immediately beneath the endless wire (K) is for the purpose of receiving the water which drains away from the pulp during the process of manufacture, and as this water is frequently impregnated with certain chemicals used in connexion with paper-making, it is returned again by a conducting spout, into the “lifter,” where, by the rotation of the buckets, both the pulp and back-water become again thoroughly mixed, and are together raised by the lifter through the spout (L) into the vat (M) where the pulp is strained by means of a sieve or “knotter,” as it is called, which is usually formed of brass, having fine slits cut in it to allow the comminuted pulp to pass through, while it retains all lumps and knots; and so fine are these openings, in order to free the pulp entirely from anything which would be liable to damage the quality of the paper, that it becomes necessary to apply a means of exhaustion underneath, in order to facilitate the passage of the pulp through the strainer.

I have frequently examined a mass of these lumps collected upon the top of the knotter, more particularly when printing papers are being manufactured, and have generally found them composed, to a very great extent, of India Rubber, which is a source of much greater annoyance to the paper maker than is readily conceived. For, in the first place, it is next to impossible in sorting and cutting the rags to free them entirely from the braiding, and so forth, with which ladies will insist upon adorning their dresses, and in the next, the bleach failing to act upon a substance of that character, the quality of the paper becomes greatly deteriorated, by the large black specks which it occasions, and which, by the combined heat and pressure of the rolls and cylinders, enlarge considerably as it proceeds.

Passing from this strainer the pulp is next made to distribute itself equally throughout the entire width of the machine, and is afterwards allowed to flow over a small lip or ledge, in a regular and even stream, whence it is received by the upper surface of the endless wire (K), upon which the first process of manufacture takes place. Of course the thickness of the paper depends in some measure upon the speed at which the machine is made to travel, but it is mainly determined by the quantity of pulp allowed to flow upon the wire, which by various contrivances can be regulated to great nicety. Among the specimens at the end, you will find one, No. 7, which was made by this machine, and which is considerably less than the thousandth of an inch in thickness,—a thousand sheets measuring but three quarters of an inch. And I would call your attention to the fact, that although so thin, it is capable of being coloured, it is capable of being glazed, it is capable of receiving a water-mark; and what is perhaps still more astonishing, a strip not exceeding four inches in width, will be found capable of sustaining a weight of twenty pounds: so great is its tenacity.

But, to return to the machine itself. The quantity of pulp required to flow from the vat (M) being determined; it is first received by the continuous woven wire (K), upon which it forms itself into paper. This wire-gauze, which resembles a jack-towel, passing over the small copper rollers (N), round the larger one marked (O), and being kept in proper tension by two others placed underneath. A gentle vibratory motion from side to side is given to the wire, which assists to spread the pulp evenly, and also to facilitate the separation of the water, and by this means, aided by a suction pump, the pulp solidifies as it advances. The two black squares on either side of the “dandy” roller (P) indicate the position of two wooden boxes, from which the air is partially exhausted, thus causing the atmospheric pressure to operate in compacting the pulp into paper, the water and moisture being drawn through the wire, and the pulp retained on the surface.

Next, we have to notice the deckle or boundary straps (Q) which regulate the width of the paper, travelling at the same rate as the wire, and thus limiting the spread of pulp. The “dandy” roller (P), is employed to give any impression to the paper that may be required. We may suppose for instance, that the circumference of that roller answers exactly to the length or breadth of the wire forming a hand mould, which, supposing such wire to be fixed or curved in that form, would necessarily leave the same impression as when employed in the ordinary way. Being placed between the air boxes, the paper becomes impressed by it when in a half formed state, and whatever marks are thus made, the paper will effectually retain. The marks seen in Specimens 2, 3, 4, and 5, have been occasioned by a hand mould, those in 6, 7, 9, and 11, are impressions given by a dandy roller. The two rollers following the dandy, marked (R) and (O), are termed couching rollers, from their performing a similar operation in the manufacture of machine-made papers, to the business of the coucher in conducting the process by hand. They are simply wooden rollers covered with felt. In some instances, however, the upper couch roll (R) is made to answer a double purpose. In making writing or other papers, where smalts, ultramarine, and various colours are used, considerable difference will frequently be found in the tint of the paper when the two sides are compared, in consequence of the colouring matter sinking to the lower side, by the natural subsidence of the water, or from the action of the suction boxes; and to obviate this, instead of employing the ordinary couch roll, which acts upon the upper surface of the paper, a hollow one is substituted, having a suction box within it, acted upon by an air pump, which tends in some measure to counteract the effect, justly considered objectionable. Merging from those rollers the paper is received from the wire-gauze by a continuous felt (S), which conducts it through two pair of pressing rollers, and afterwards to the drying cylinders. You will observe, that the paper, after passing through the first pair of rollers, is carried along the felt for some distance, and then turned over, in order to receive a corresponding pressure on the other side, thus obviating the inequality of surface which would otherwise be apparent, especially if the paper were to be employed for books.

The advantage gained by the use of so great a length of felt, is simply, that it becomes less necessary to stop the machine for the purpose of washing it, than would be the case if the felt were limited in length to its absolute necessity.