The Riverside Mill 1921

Here the wood is cut into slabs five-eighths of an inch thick diagonally across the grain, to assist the chemicals in penetrating through the pores of the wood. These slabs are broken up into chips five- eighths of an inch long by a huge revolving fan and air blasts clean the chips and sort them into sizes. This building also houses our machine shop, carpenter shop, storehouse, box shop and dry lumber storage. The chips drop on an endless belt conveyor which carry it to the digester house.

These digesters are horizontal revolving boilers lined with steam pipes, in which the wood chips are cooked under pressure by indirect steam heat in a solution of soda ash or dry sodium carbonate, made caustic by adding quicklime. The resulting caustic soda is a powerful alkali which dissolves the 50 per cent. of intercellular matter in the wood, but, if the cooking process is properly carried on, leaves the cellulose unharmed. The average cook in this mill takes twelve hours. I t could be shortened by various means, but each short cut weakens the fibre and lowers the quality. Careful cooking is' the second important step in the manufacture of good paper . When the cook is completed, the caustic soda liquor is drained off and the wood is dumped into the two parallel troughs under the digesters, housing conveyors, which carry it to the rotary drainers.

This is a triple effect Newhall evaporator designed by a Philadelphia engineer and built in a Philadelphia plant. The black liquor of a specific gravity between 7 and 8 degrees enters the first effect, where it is boiled by the steam generated from the waste heat of the rotary incinerator. The hit vapor from the first effect, aided by 6 inches of vacuum, boils the liquor in the second effect. The vapor arising from the second effect, aided by 27 inches of vacuum, continues the evaporation in third effect until the liquor reaches a density of 35 degrees Baume, when it is pumped over to the rotary incinerator.

Rotary Incinerator

Here you will see a stream of liquor running from a pipe into aflame produced by burning soft coal in a forced draft. All of the intercellular and organic matter which in the digesters dissolved, in the alkali solution is burned out by the flame and goes up the stack as vapor, but the soda ash becomes a glowing cinder, drops to the floor of the drum, and by the rotating motion is worked out of the end where you see it dropping into a conveyor. The glowing cinder is known as "black ash", to distinguish it from soda ash which has not been used, common called "white ask." The recovery of soda ash by this :process averages from 85 per cent. to 90 per cent., which reduces the first cost of soda ash from a present price of about $1.60 per hundred pounds to from 14 cents to 16 cents per hundred , This mill is a firm believer in every economical process which will reduce the cost of paper without affecting its quality. This conveyor carries the black ash to the lime house.

Here it drops into large tanks with agitators, where it is dissolved with hot water. When it reaches the proper density it is pumped into the causticizing boiler, where fresh soda to make up the 10 to 15 per cent. lost in reclamation and; lime ;sufficient ;to thoroughly causticize the liquid are added. The solvent in this case is "black water," which is the hot water used to give the final cleansing to the pulp in the rotary drainers described in paragraph five. Heat units have been consumed in raising the temperature of this water, and it contains a small amount of fibre and soda ash; too little of the latter to evaporate. Economical operation demands that none of these elements shall be lost, and so they are utilized in the manner described. The remaining floors of the evaporator house are ,; given over to the filtration, settling, storage and other steps in the handling of caustic and black liquors. We will now resume the examination of the principal process of pulp making at the number nine mixing tank. Cooked wood, now called pulp, which you will remember is cellulose or fibre, coming over from the rotary drainers is here mixed with water and thoroughly stirred. by the revolving propellers. It is next pumped over to the knotters.

This device is a rapidly vibrating screen with small slits which receives the solution of water and fibre. The vibration causes the fibre to work rap- idly through the screen, but knots and other Un- cooked particles of wood cannot get through and they are cleaned out by hand and sent to the rubbish heap. The knotter received its name when all paper was made from rags and knots in the threads had to be screened out before the paper was made. I t is equally efficient, however, "in eliminating knots of wood from further participation in the process. The fibres which work through the screen are from one-twenty-fifth to" one eighth of an inch in length, very thin, and in shape not unlike a minute blade of grass. Under the microscope they are seen to have around their edges thirty-five to forty small hooks, which playa large part in the paper-making process. The water carrying the fibre is next ,pumped over to the wet machine

If you will dip your cupped hand into the brownish water which is gurgling and foaming at the end of this machine, you will find that the water which you bring out has a brown sediment in it. This sediment is made up of numberless fibres such as we have been striving to get ever since the wood started through the chipper. The water is sprayed against a mould or cylinder , where the fibres, collected by induction, form a slab or heavy sheet which is picked off by the couch roll. The couch roll (pronounced kooch, the o as in spoon) is a wooden core or frame thickly covered with woolen felt. It takes its name from the same source as the word couch as commonly applied to a lounge or bed and it means "to lay together closely." The fibre then passes through a light "squeeze" roll to eliminate some of the water and then under the press roll, which gives consistency to the rapidly forming sheet. Moisture rolling, pressing and beating reproduce with wood fibres the same result as when these processes are applied to animal fibres, such as hair or wool. They mat or felt the fibres into a solid mass in which each one of those thirty-five or forty little hooks previously mentioned fastens itself into a hook on some other fibre and gives the mass consistency. You can see on the upper roll the brown mass which is holding together with sufficient tenacity so that it can be laid off on the woolen felt as a. sheet of unbleached soda pulp. For ease of transmission the sheet passes under revolving rolls set with pegs, and is torn into strips which pass out over the apron into the conveyor to be taken up to the fourth floor to the poacher.

These are fitted with agitators and drainer bottoms. The clear water is poured in from the top, percolates down through the mass and out at the bottom until every particle of bleach has been washed out. The water is then turned off and the pulp is left to drain. When it is thoroughly drained it has reached a consistency which prevents the agitators from turning. Water turned in from the top filters through without loosening up the pulp. It is, therefore, necessary to float the pulp by admitting water from the bottom. The pulp floats on top of the water just as wood does and gives an opportunity to start the agitators, and by adding water to produce a mixture liquid enough to be dropped by gravity into chests on the floor below. These chests are fitted with revolving paddles, and in them the fibre is still further diluted by water until it is ready for the wet machine. The once brown mass transformed to a beautiful creamy white by the action of the bleach is then . conveyed in solution to the ground floor of the pulp .mill, run over wet machines just as it was before bleaching and as pieces of bleached soda pulp it is conveyed to the storage bin on the second floor. This ends the process of soda manufacture.

The size mixing department which is easily detected y the odor. Here also is the the clay mixing platform. The best clay for fine paper making comes from a small territory about twenty miles square in Cornwalls, England. This is th famous English china clay, used in the manufacture of the best crockery. It has gone through a long process of washing and screening to eliminate all dirt, mica and other impurities. It is mixed with water and goes into the beaters in solution. The beginning of paper manufacture is in the beater room.

In these large tubs of capacities varying from 1000 to 2000 pounds, the paper-making ingredients are mixed in their proper proportions. First the soda pulp comes over as "slush," which is the pulp mixed with 95 per cent. to 98 per cent. water and thoroughly agitated. Then sulphite pulp or half stuff made from rag fibre is added and the mixture is thickened to the right consistency by adding 50 per cent. dry soda pulp from carts or boxes on wheels. A beater or beating engine usually has two revolving cylinders, one a very heavy cylinder, known as the beating roll, reaches to the bottom of the engine and bears a number of knives on its surface. These knives work in conjunction with similar knives standing up from a bedplate on the bottom of the engine underneath the beater roll. The fibres passing between these knives are pounded and beaten, thus increasing their toughness. , The other cylinder is fitted with. :fine wire gauze, through which excess water filters into a number of bucket compartments inside the cylinder and is carried off through the hollow axis to the waste pipe. You will probably observe that many of our beating engines have three cylinders instead of two. They were made to our order by the Moore & White Company of Philadelphia. The extra cylinder is an additional beating roll, and it emphasizes the importance of beating in the production of good paper. The harder papers, such as ledger, writing and envelope, require long-continued beating to bring the fibre to the right strength and condition.

This operation is one of the most important and most delicate processes in the manufacture, requiring experience, skill and careful manipulation. Not only does every class of fibre demand its own special treatment, but this treatment has to be modified and varied in each case to suit the qualities and sub- stances of the papers to be made from it. The time required for the beating process varies from three to four hours up to ten or twelve. hours, and even more. Hamilton papers are "beat off the plate," that is, the beating roll goes down on the bedplate when the pulp goes into the beater, and every turn of the roll adds to the strength and refinement of the fibre. The process is never hurried. Long experience has taught our skilled operatives how much time is required to produce' the best results with each grade of paper, and they are keenly interested in giving their important part of the job exactly the right touch. Filler, color and size are each added at some stage of the beating operation. Size is the last to go in, .and by a simple device of our own it is applied ill the way best suited to distribute it evenly through the mixture. When the beating is finished, the plugs in the bottom of the engine are removed and the pulp drops to the stuff chest, the stuff box and the Jordan engine.

The Stuff Chest- Here the "stuff" has a consistency of between 95 per cent. and 98 per cent. water, and it is constantly agitated by the large revolving paddles, so that the fibre will remain suspended in the solution and not sink to the bottom. As needed for the paper machines, the stuff is pumped up into the small box called The Stuff Box - This determines the amount of paper the machine will make each hour. The interior of the box is so arranged that only the amount of stuff required per hour for the predetermined amount of the run can pass through it. The overflow passes back into the stuff chest. The stuff feeds directly from the pulp box to the The Jordan Engine. This important part of the paper-mill machinery is a conical-shaped shell fitted on the inside with steel or bronze knives. In our cases the knives are bronze, because of their better wearing qualities and more accurate results. A revolving cone studded with similar knives fits inside the shell. It can be adjusted to bring the edges of its knives closer to the knives of the shell or to make the distance between them greater. The purpose of the Jordan is to still further re- fine the fibre to make it of uniform length, and to adjust that length to the kind of paper which is wanted. The closer the knives are to each other, the shorter the fibre will be. The length of time stuff is in the Jordan is regulated by a simple but effective device which looks not unlike the pulp box. It has a partition up and down the centre, over which the stuff must flow to get out of the engine. The partition is removable, section by section, and it is built up or taken down, according to the desire for "slow" or thick stock or "free" or thin stock. After leaving the Jordan the stuff passes on to the sand traps, but in this mill it passes over a de- vice peculiar to our process. The pipe leading into the sand traps contains a powerful magnet to catch and hold any iron, no matter how fine, which may have found its unwonted way into the fibre. The manufacture of good paper is a constant fight against foreign substances which leave their mark. You have noted at the various steps in the manufacture of soda pulp the methods and devices to eliminate all but the pure fibre. You will observe the same care in the manufacture of the paper. First the sand trap on the Jordan, then the magnet, and next The Sand Trap, The Screens and The Head Box.

The Sand Trap - Here the force of gravity is counted on to pull down from a swiftly moving stream of stuff and sand, metalic substance or other foreign bodies which collect behind narrow strips of wood set across a serpentine channel in the bottom, lined with rough felt, while the lighter fibre is carried along by the current to The Screens - The brass plates are perforated with long skits about 12 to fifteen thousandths of an inch in width, which permit the fibre to pass through but reject the larger impurities. You will admit that fibre has had a struggle, a cross between endurance contest and an obstacle race, to get thus far in the process, but its troubles are nearly over. It flows out from under the screens to The Head Box -This is arranged to provide an even flow, under a spray of water to keep down the froth from the rosin size and out to The fourdrinier Paper Machine.

Prior to the opening of the nineteenth century all paper was made by hand on a mould of fine wire cloth with a removable frame of wood, called the "deckle," extending slightly above the surface 'of the mould and intended to keep the pulp from running off. To form the sheet, the paper maker would dip the mould into a vat containing the prepared pulp and lift up just enough to make a sheet of the required thickness. As soon as the mould was re- moved from the vat, the water would begin to drain through the wire cloth and to leave the fibres on the surface in the form of a coherent sheet, the felting or intertwining being assisted by a lateral motion or "shake" given to the mould by the workman. The movable deckle was then taken off and the mould given to another workman, called the "coucher," who would turn it over and press it against a felt, thus transferring or "couching" the sheet from the wire to the felt. The sheets were then piled one above another alternately with pieces of felt and the whole was then subjected to strong pressure to expel the water. The felts were then removed and the sheets were again pressed and dried. The hand process is described at somewhat greater length than its relative importance in the industry would seem to justify, because it makes easier an understanding of the paper machine. For the machine does exactly as the hand paper maker did, and even the nomenclature survives, as will be seen as we go along. In paper making it bears the same relation to the hand mould as in printing the rotary press does to the hand press.

The machine takes its name from Henry Four- driller, the proprietor of a mill at Dartford, in Kent, who in 1803 built the first machine at Frogmore, Herts, after the plans of its inventor, Louis Robert, a clerk in the employ of Messrs. Didot, of the Essone Paper Mills in France. This first machine worked comparatively well, but by subsequent improvements by eminent engineers-Dickinson, Causon and Crompton among others-it has been brought to its present state of perfection. The stuff passes out of the head box under two slice bars, which serve as a dam to regulate the amount of water permitted to pass through with the fibre- the more water, the thinner the sheet-on to an end- less band of woven wire cloth of about eighty meshes to the inch. The wire is supported by a number of rollers-known as tube rolls-to prevent oscillation and assist the passage of water through the wire. The frame of the machine is hung on strong hinges and a slight horizontal motion is imparted to it by mechanical means. The object of this shake is to crisscross the fibres by causing some to turn across the machine instead of laying the length of the ma- chine, as the flow of the current would naturally cause them to do. The fibres are thus intertwined and the closing of the paper web is started. The end of the wire nearest the head box can be raised and lowered about six inches to assist in regulating the speed at which the pulp flows over the wire. The thickness of paper is determined by the speed with which the wire moves and the flow of pulp must appropriate the speed of the moving wire if paper of uniform thickness is to result.

The width of the sheet is regulated by two continuous straps of vulcanized rubber about one and one-half inches square, one on each side of the wire. They ate called "deckle straps," and they take their name from the "deckle" on the hand mould, and by holding the pulp on the wire they serve the same purpose. Deckle edge paper was originally paper with the rough edge left by the contact of the pulp with the deckle of the hand mould or the deckle strap of the machine. The deckle edge desired on certain high- grade book papers is now generally produced, how- ever, by cutting the paper with a fine stream of water just as it leaves the wire. The derivation of the word is interesting, as it comes from the same source as the word of common use, "deck," a covering or shelter. As the pulp nears the far end of the wire, it passes over a suction box, the open end of a powerful pump sucking the water through the wire out of the paper. It then passes under the dandy roll.

The Dandy Roll - A cylinder of wire which closes the surface of the paper by slight pressure. If .paper is to be water- marked, the design is outlined in thin wire soldered fast to the outside surface of the cylinder. The pressure of the cylinder displaces the fibres according to the design and leaves the paper infinitesimally thinner where the fibres are displaced, so that the watermark is visible when the paper is held to the light. "Laid" paper is made by a dandy roll with raised wires running the length of the cy1ind~r at definite distances with tying wires at regular intervals. If the tying wires run the length of the roll, it produces "reverse laid." The plain dandy to produce un- watermarked wove paper leaves no mark. The production of clear-cut watermarks requires slower running of the machines and correspondingly increases the cost of the paper. The second suction box is beyond the dandy roll and here more water is extracted. Moisture still remains in the web of paper, but this is the last point at which water is extracted in quantity. It seems fitting to observe that each ton of paper passing over the wire has used nearly 25,000 gallons of water to dilute it, so that this is rightly called the "wet end" of the machine. The important part which water plays in paper manufacture cannot be overestimated. If uniform cleanliness, color and quality are to characterize its paper, a mill must have an ample supply of clean water of a temperature varying from 50° to 55°. In most mills this result is sought! for by pumping water to a height for settling and filtration, letting it run down to the mill, where it is usually refrigerated in summer or run over steam coils in winter, but it is almost impossible to keep it uniformly clear.

The Hamilton Mills have a ninety-year lease on one of the largest springs in eastern Pennsylvania, located at Spring Mill, which supplies 3000 gallons per minute of clear , pure water through the company's own pipe line at 54° temperature the year roumd, year in and year out, without filtration, pumping or refrigeration. Before you go, ask to see the eight-foot tank containing water so clear that you could read through it and to have a good cold drink of it. From the last suction box the half -dried sheet of pulp passes between a brass press roll and a felt- covered couch roll with adjustable arms to raise and lower it according to the need for pressure. The couch roll consolidates the sheet so that it can be carried on endless felts between several sets of press rolls which eliminate more moisture, and as far as possible obliterate the marks of the wire cloth from the under side of the web. The paper is now carried over The Dryers.

These massive cylinders are hollow and steam is introduced in the interior. The paper is carried around and held tight against the hot dryers by a cotton or canvas belt, called a dryer felt, so that the paper will not cockle in drying. There are a number of pretty problems to be solved on the drying machine. The process must be as slow and gradual as is possible, so that the change in the fibres of the web, due to rapid contraction in drying is not so excessive, and the heat required at one time is not so great nor so likely to damage the quality of paper. Because of the speed at which the dry end must run to keep up with the wet end, this is accomplished by having a large number of rollers, offering the largest possible heating surface within the limits of available space. The heat is so regulated that it is gradually increased, and the speed at which the web of paper travels is arranged so that no undue tension is placed upon the paper or the web would be broken. At the end of the dryers are the calenders and slitters

These vertical stacks of chilled iron rolls, bored and heated by steam produces the machine finish on the paper. Wherever the paper passes. between two cylinders, it is called a "nip." The combined action of heat and pressure produce a glazed finish, the height of which is determined by the number of "nips" the paper receives. If a higher finish than a machine finish is desired, the sheet is moistened by a fine spray of water and supercalendered. The supercalender is a stack of alternate chilled iron and paper rolls. The latter are made from disks of paper put on a mandrel and subjected to such pressure that the disks become a homogeneous roll with the edge of each disk on the circumference of the roll. The friction created between the rolls of different materials and the moist paper passing between them imparts a high gloss to .the paper. The paper from the calender passes to mechanically operated reels which roll it in the full width sheet. As a reel is finished it is swung over in a half circle and while a new reel is starting the paper is run under the slitter.Here sharp circular knives or shears are set at the required distance apart to give the sheet of desired width and to trim off the rough deckle edge. A very interesting device for making rolls of the paper coming from the slitters is the roller bearing, two revolving horizontal cylinders on which a round wooden core is placed. The motion of the rollers is imparted to the core resting on them and the paper is fed over the core at a slight tension and is made into rolls.

Eight rolls of paper are set in place on the cut- ters in two parallel rows, and the paper from them is led under a knife set in a revolving cylinder. This cylinder is belt driven from a cone drive, and the belt can be moved in and out on the cone to make the knife cylinder revolve slower or faster. The speed of its revolution determines the length of the sheet of paper. The faster the knife revolves, the shorter the sheet. Writings, ledgers and offset are trimmed on the power trimmers, familiar to all printers, in order to give the exactness of size and angle necessary to ac- curate register. The cut sheets fall on endless belts and are car- ried to girls seated at the cutter tables, where they are inspected and arranged in piles. This work can . be done mechanically on certain grades of paper, but the vast majority of the Hamilton product is better handled by the skill and intelligence of the cutter girls. Many papers are mechanically counted by devices set on the revolving knife which do not make any allowance for lost sheets when the web breaks down and the knife makes several revolutions with no paper passing under it. Hamilton papers are hand counted.

Here skilled fingers assure an accurate ream count. Here, too, the paper is trimmed when trimming is a part of the process, and the finished paper is packed in the way which will assure safe carriage and delivery to the consumer in a condition consistent with the quality of the paper. Writing and ledger is ream wrapped and sealed, and is carried in stock in standard weights and sizes. Roll intended for shipment in carload lots are carefully protected around the edges and wrapped. Book and envelope papers are inter-lapped and wrapped in bundles, or put up in skeleton frames when moving in carload lot shipments. All writing, ledger and offset in sheets and other papers in less than carload lots are packed in cases of our own making. The wrappers used here, both light and heavy, are made by us, so that we can be sure of their quality. These are all precautions intended to help in giving the consumer paper in as good condition as if his plant was next door to our mill.

The descriptive matter in this booklet is printed on some Hamilton papers which we hope will serve, together with the text, in recalling to your memory the principal points in the manufacture of good paper. Hamilton papers are good. They are made good by First-Careful cooking of the wood going into our soda pulp, which makes easier each succeeding process in its manufacture. Second-Particular methods in the beating and refining of the fibre. Third-Running the machines at the speed best designed to close the sheet and give the desired finish. Fourth-By the control of a water sup- ply of uniform purity, cleanliness and temperature. Fifth-By the care and attention of a loyal, efficient, well-trained working force now associated with us in many instances in the second generation.

In 1961 The W. C. Hamilton & Sons Paper Mill became a subsidiary of Weyerhaeuser Company until 1980 when the plant was purchased by Simpson Paper Company.