"The Wisconsin Years," from
My First Eighty Years (and then some!)
Lyle Arthur Seefeld
Copyright Ralph L. Seefeld and Carol
Howman. This book may not be reproduced or copied
in any manner without the written consent of Ralph L. Seefeld
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Chapter 20: Paper Mill Days - My Laboratory Job
It was an early spring morning in 1931 when I reported to work at my new job at the Tomahawk Kraft Paper Co. laboratory. Alden Extrom, who had been a high school classmate of mine was in charge of the lab. Our high school didn't teach chemistry while we went there, but Alden had gone to the University of Wisconsin at Madison, and now knew enough chemistry to take charge of the lab. He showed me around the lab and introduced me to Fred Buran, who showed me how to do the routine chemical tests on the cooking "liquor" which was a strong solution of sodium hydroxide (lye) and sodium sulphate. The sulphate was unique to the "Kraft" pulping process, and was responsible for the great strength of Kraft paper.
The laboratory was on the second floor of a small two story building and connected to the main paper mill building by an enclosed hallway. It consisted of four rooms, the main lab with a central chemistry bench with two sinks, and two wall benches, a smaller "paper-making" lab with a miniature pulp "beater", two square "paper machines" and a steam heated dryer, and two offices, one for the chief and one for us "chemists."
When I started working in this lab the personnel included Extrom, the chief, Fred Buran, a chemist (who lived in the Hartwig house!) and myself. Kermit "Ole" Olson came along a little later. Fred Buran was assigned the job of teaching me how to perform the routine chemical tests which were necessary to the pulp making and bleaching processes.
In order for the reader to understand how the laboratory fit into the paper making operation, I'm going to try to explain a little about the process of making paper. The raw material, spruce, hemlock and pine logs, came to the mill on railroad cars. (By the M.T. & W!) The logs were stored in a huge storage yard and transported to the "chip mill" as needed. There they were tumbled in a huge knife-equipped rotary drum where the bark was removed, and then sawed into short lengths before being fed into the chipper. This chipper was a large wheel with knives that reduced the short logs to small pieces the size of ordinary dominoes and smaller. A long conveyor belt carried the chips up to the top of a tall building which housed a big storage bin with a funnel shaped bottom. Under the storage bin was a room containing two "digesters," cylindrical vessels with cone shaped ends. To start a digester "cook" the top end was opened, chips were allowed to fall in from the bin above, and the cover bolted in place. Then the proper amount of cooking "liquor" was pumped in, about a hundred pounds per square inch of steam pressure applied, and the digester slowly rotated end over end while it cooked for about an hour.
At the end of the cooking period, the digester was stopped at its starting position, and a large valve at the bottom was opened, allowing the steam pressure to blow out its contents into the room below. Here the pulp was washed free of the cooking liquor and pumped to storage tanks. The spent cooking solution, while it had done its job of separating the wood fibers, still contained valuable chemicals, which, after proper treatment, could be re-used for cooking pulp.
Sometimes, if the storage tanks were full it was necessary to store pulp in "lap" form. It was pumped to a machine which removed most of the water, creating a continuous thick sheet about a quarter inch thick and several feet wide. The lap machine operator cut this sheet into lengths and folded them into batts, or "laps" about as big and heavy as a strong man could lift and piled them on a truck to be moved to a storage area. If pulp had to be shipped to another mill, this was the form in which it was transported.
At this point, the pulp, whether in laps or in water suspension in storage tanks, was still not ready to be made into paper. Under the microscope, a typical kraft pulp fiber is seen to be roughly cylindrical in cross section, long and slender with tapering ends. Paper made from unbeaten pulp would lack the required strength because the relatively smooth fibers could be pulled apart rather easily. So the pulp is pumped into a "beater." This machine is essentially a large oval vat with a partition in the middle around which the pulp circulates, passing between a huge roller equipped with steel bars and a stationary plate with steel bars. In the process the fibers are flattened and the ends splintered or frayed, so they interleave in the paper and contribute to its strength.
And now comes the tricky part, making the prepared pulp into a continuous sheet of finished paper. This is done on a huge Fourdrinier machine, named for the Frenchman who invented it in the nineteenth century. This machine is something like a city block long and consists of two major sections: the "wet end" where the paper is formed, and the "dry end", where, of course, it is dried. Tomahawk Kraft had two machines, one made paper 120 inches wide, and the other 144, if I remember right. The first unit at the wet end was the "headbox" as wide as the machine and kept pumped full of pulp suspended in water and thoroughly mixed. At the bottom edge of this box, an adjustable slot allows a steady stream of pulp and water to flow to the next unit, which is the "wire."
The Fourdrinier "wire" is a fine bronze screen, somewhat wider than the sheet of paper it is to form, and made into a long endless belt. The upper part of the loop is supported by a flat bed of long metal rollers, which must be kept level. When the machine runs, the stream of pulp from the headbox flows out over an oilcloth apron (probably plastic these days) onto the moving wire while gravity removes most of the water. Near the end of its travel on the wire, more water is removed by a suction box on the underside, and by the time it reaches the end of the wire it is dry enough to be self-supporting. So it is then fed to a series of "presses" which are metal rollers with a felt belt running between, and more water is removed.
From here it goes to the dryer. By far the longest part of a paper machine, it consists of two horizontal rows of huge steam heated rotary drums, one above the other, with wide canvas belts threaded around them. The wet paper from the presses passes between canvas and the first roller in the bottom row, then between the canvas and the first roller in the upper row, then between canvas and the next roller in the bottom row and so on until it comes out the far end, thoroughly dry.
When paper comes off the dryer it still isn't finished. Passing it between two or more (sometimes steam heated) vertically arranged heavy steel rollers in a "calender stack" gives it the desired smoothness and then it is wound on big rolls to be taken to the "finishing room" where it is cut to size and packed for shipment. One of the trickiest parts of running a paper machine is controlling the speed of the various parts, since if all parts ran at the same speed, they would tear the paper apart. This is because the paper shrinks as it dries, so as it progresses through the dryer, the parts must run a tiny bit slower. Adjusting the speeds was a strictly manual operation sixty years ago, but today is most certainly done automatically by computer.
So far we haven't seemed to need a laboratory, or have we? Remember when the cooking "liquor" was pumped into the digester to cook the wood chips? Well, to make sure it was of the proper strength, a sample was analyzed in the lab. And remember when I said the spent cooking liquor was recovered, reclaimed and re-used? The lab played an important part here, too. The used chemicals washed from the pulp are quite dilute, so they are sent through an evaporator, where most of the water is removed. They are then fed to a "soda recovery" furnace, where the lignin and other waste products from the cooking procedure are burned off, leaving only the molten sodium salts which are immediately dissolved in tanks of water. When the new solution reaches the proper strength (as determined by lab tests) it is pumped to a "causticizing" tank and a quantity of quicklime (tested by the lab) is added and the contents thoroughly mixed. The lime combines with the recovered chemical to form sodium hydroxide (lye) which remains in solution, and calcium carbonate which forms in small particles and settles to the bottom so the clear liquor can be siphoned off for cooking another digester of chips. At least that is the way it is supposed to work. A little later I'll tell you about one time when it didn't work, and what I did about it.
The process I've described so far results in only one kind of paper, the brown kraft used to make grocery bags and the outside and inside layers of corrugated cardboard boxes. The Tomahawk mill didn't often make this kind, as they preferred to make specialty papers, those requiring dyeing, bleaching, or both, to their customers' specifications.
Dark colored papers could often be made by simply adding the proper dyes to the brown unbleached pulp. To determine what quantities of which dyes to use was a job for the laboratory's miniature "paper mill." The laboratory beater was filled with pulp, and measured quantities of dyes were introduced, and "fixed" by adding a solution of alum. Then a sample of the dyed pulp was made into a sheet of paper in the lab's "paper machine." This "machine" was merely a square of the same fine mesh bronze screen as the big machines used, soldered across the top of a square funnel which was set into the top of a bench. A drain and suction pipe were fastened to the bottom end, and provision was made to fill it with water. The removable part consisted of what looked like a heavy cast iron box with no bottom. The bottom edge was fitted with a rubber gasket so it wouldn't leak when placed on the screened funnel and filled with water.
To make a sample sheet of paper, a small quantity of the pulp from the beater was placed in this water-filled box, and thoroughly stirred. Then the bottom valve was opened, the water drained out, suction was applied and the box removed. And there on the screen was an extremely wet layer of pulp. More water was removed by placing a sheet of heavy, soft felt on it, and rolling it with what looked like an overgrown rolling pin. When the felt was removed, the layer of fibers adhered to it, but was now dry enough to be lifted off and placed on the dryer. This dryer was very much like a photograph dryer, being merely a steel box with a curved top, with a canvas cover held down by a heavy weight hanging on the front edge. In a few minutes, the paper sample was dry, and could now be compared with the sample we were supposed to match. For this purpose, there was a small black-painted booth which was lighted by an incandescent "daylight" lamp.
To make light colored or brightly colored papers, the pulp had to be bleached before it was dyed. The bleaching was done in the beater by adding a measured quantity of "bleach liquor" or calcium hypochlorite, a close relative of the common Purex or Clorox bleach. The mill made its own bleach in a long, narrow room containing the chlorinating tank and several bleach storage tanks. To make bleach, the chlorinating tank was nearly filled with water, the circulating pump was started and a measured quantity of lime was added. When it was thoroughly mixed, chlorine from a tank car on the railroad track nearby was injected into the tank, and the chlorination proceeded. When the process was completed, a sample was taken to the lab for analysis to make sure it was of the required strength. It was then pumped into one of the storage tanks from which it could be pumped to any of the beaters through a system of pipes and valves. A buzzer system with a pushbutton at each beater signaled the bleach plant operator to pump liquor.
When pulp was being bleached, the operation was supervised by the laboratory technician on that shift, who determined when the process was finished, and who made sample sheets of paper from the pulp to make sure it was the right color. One night I was working the "graveyard" shift (midnight to 8:00 AM) when bleaching was being done. We pushed the button to tell the bleach man to pump liquor, but no bleach came. After punching that button several times with no results, I hurried back to the bleach plant to see if there was a problem. When I opened the bleach room door I was greeted by a cloud of yellow-green chlorine gas! I held my breath while I turned off the chlorine and then hurriedly put on a gas mask which was kept handy for just such occasions. Then I looked for Paul L'Abbe, the operator, and found him sitting on a bench, leaning against the wall, fast asleep! I quickly woke him and ushered him out of there, and then went around opening all the windows so fresh air could replace the chlorine gas. Paul had been making a batch of bleach liquor, but was asleep when it was time to turn off the chlorine, so when the lime had been fully chlorinated, the incoming gas had no place to go but out into the room. And the source was a huge railroad tank car filled with chlorine!
It was possible to bleach kraft pulp enough to make white paper, but, since that much bleaching weakened the fibers so that the result was no stronger than the cheaper sulphite papers, it was hardly ever done. Many kraft mills experimented with alternate bleaching methods and Tomahawk Kraft was no exception. The method experimented with at this mill involved two steps, a preliminary direct treatment with chlorine alone, with a subsequent addition of a smaller amount of regular bleach. Both steps were done in the beater, and the chlorine was injected into the pulp in the beater by a huge version of what chemists know as a filter pump, or aspirator. This device was connected to a two-inch water hose and arranged to discharge into the beater. The flow of water through the aspirator created a strong vacuum at its side connection, which was connected to a 2000 pound drum of chlorine by means of iron pipe.
So for the first test, the water was turned on, and then the chlorine valve was opened slightly, and we started chlorinating pulp. Judicious control of the chlorine valve prevented any of the gas from escaping into the room. Soon the pulp began to change color, eventually becoming a pale orange, and presumably more easily bleached than when it was brown. So the chlorine was turned off, and then the water was turned off, and then some of the regular bleach was added. This pulp did bleach better than the untreated variety, and when it was ready, the beater was emptied into the storage tank on the floor below. Then it was filled with more raw pulp, and the water and chlorine were turned on again. After only a very few minutes, however, I began to smell chlorine. I quickly turned off the valve at the tank, but by that time the room was yellow-green with chlorine gas. We all put on gas masks, opened all the windows to air out the place, and then looked for the leak.
We found a hole in a cast iron elbow somewhere in the middle of the pipe line, so we started to dismantle it so it could be replaced. At the first turn of the pipe wrench, the whole chlorine line fell apart as though it had been only puttied together! So a new chlorine line was put in place, this time made of double extra heavy half inch iron pipe. Since this pipe had to use standard fittings, its outside diameter was the same as any half inch pipe. The inside diameter, however, was only about a quarter inch in diameter, making it look more like a rod with a hole in the middle than a pipe. After the new pipe was in place, the system worked fine for the first batch. But when the second beater load was started, the whole scene repeated itself, and the iron pipe fell apart.
Clearly there was something wrong with the system. After some study, the cause and the solution were found to be ridiculously simple. When the system was shut down, the chlorine was shut off first, but the aspirator continued to pump, creating a vacuum in the chlorine line. Then when the water was shut off, stopping the pumping, the vacuum drew water into the iron pipe, and the next time the chlorine was turned on, the combination of iron, water and chlorine created ferrous chloride, which is soluble in water! In other words, the chlorine and water were dissolving the pipe. The remedy was simply a relief valve in the chlorine line, opened before the water was stopped, leaving the iron pipe dry and able to safely carry chlorine. Our gas masks sure got a workout before this problem was solved!
Paper mills are notorious for using tremendous quantities of water. The Tomahawk Kraft mill, being only a stone's throw from the Wisconsin, used water from the river after running it through a chlorinator, and, in those days before pollution concerns, dumped its waste fluids into the same river. This worked just fine except when a wind from just the right direction made the waste water accumulate around the water intake. In the laboratory, distilled water was used in all the analyses, and we made our own distilled water, using a steam heated still. We stored distilled water in two large glass carboys, fitted with siphons for withdrawing water. Some times, on those occasions when the water supply to the still was exceptionally bad, the still would boil over, sending a stream of dirty brown water into one of the jugs. It's a good thing we had two!
Another of the laboratory's responsibilities was to maintain the equipment used for routine testing of paper samples taken right from the machines during production runs. The testing instruments were all assembled on a big table in a small laboratory near the place where paper came off the machines, and were used by designated paper testers, one for each shift. The most used test instrument was the Mullen Tester, which measured the bursting strength of the paper. Other test machines measured the tensile strength (in both directions,) the Elmendorf Tear Tester, which measured the paper's resistance to tearing, and a Schopper Folding Tester, which mechanically folded paper samples back and forth until they broke.
Another quality of the paper that was routinely measured was its moisture resistance. In these tests small squares of the paper were sprinkled with an indicator powder and floated on the surface of the water in a small container. This indicator was ordinary powdered sugar to which a small amount of a dye called methyl violet was added. This dye in its dry state was a light green and the mixture of dye and sugar was almost white. The slightest amount of moisture, however turned the dye to a vivid purple, coloring the sugar. A stopwatch was used to measure the length of time the samples floated on the water before the first purple color appeared. When I first watched this test being performed, it seemed to me to be awkward and inaccurate, since the technician could never be sure he started the stopwatch at the exact instant the samples touched the surface of the water. So I built a device to make these tests easier and more accurate. It was a small copper box, nearly filled with water, with a small copper grate which normally was held high and dry above the water. To perform a test, the samples were placed on the grate, sprinkled with indicator, and then a lever immersed the grate in the water, leaving the paper floating on the surface. Now it was easy for the operator to float the samples and start the stopwatch at the same time.
During the last year or two I worked at the mill, one of the paper testers was Elmer Foster. The same Elmer Foster who had married Eugene Field's youngest daughter Ruth, and who had arranged my summer job in my high school years, working for his sister-in-law Mrs. Mary French Field Englar, as explained in Chapter 14. When I first knew Elmer he was a successful lumber broker in Tomahawk, but the depression had wiped out his business,, so he was working at the mill while he developed another enterprise, making animal traps which did not harm the animals it caught. In later years I occasionally saw an ad for his traps in various magazines so I assume his new venture was successful. Elmer has been gone for many years now, but the last I knew his son Bill still lived in the house he grew up in on the east bank of the Wisconsin River, in South Tomahawk.
Earlier in this chapter I mentioned a time when the mill's process for recovering used cooking chemicals and converting them to usable form developed a serious problem. After the chemicals used in cooking a digester full of pulp were collected, concentrated and burned to eliminate the organic residue, they were dissolved in water and pumped into huge tanks where lime was added and the mixture was stirred. The recovered sodium carbonate reacted with the added calcium oxide to form sodium hydroxide, which stayed in solution, and calcium carbonate, which was in the form of a precipitate, and settled to the bottom after agitation stopped, so the clear liquor could be drawn off and re-used. This was the way it was supposed to work.
The company bought lime by the boxcar load, and one time they got a shipment that gave them nothing but trouble. The lime was so finely divided that after it was added to the tanks and stirred, it refused to settle, staying in suspension instead. Since pulp and paper making is a continuous process, they couldn't stop cooking pulp just because the liquor wasn't clear. And as long as they were making natural kraft paper, there didn't seem to be any problems. However, one day they were running a paper that had to be made from pulp that was bleached and then dyed. And the pulp which had been cooked with that muddy looking liquor wouldn't bleach properly. Instead of bleaching to a pale orange color like it should, it turned a sickly pale green, and made it impossible to make the paper exactly the right color.
I had been reading some of the paper making books we had in the lab, particularly one by Sutermeister, entitled "Chemistry of Pulp and Paper Making." I remembered a paragraph in which he dealt with liquor settling problems, and decided to try something. I was working one of the night shifts, so there was nobody in the lab to consult, so I found a bucket, filled it with starch from a supply in the paper mill, carried it to the pulpmill chemical recovery room and dumped it into a tank of liquor which had just had lime added. And when the agitator stopped, the starch glued those minute particles together into larger clumps which rapidly sank to the bottom. That was the clearest tank of cooking liquor they had seen around there in a long time!
As I said, I was working a night shift, and was home the next afternoon when my boss phoned and asked me to come down to his office. When I arrived, he said something like: "What do you mean by interfering with our manufacturing process?" After listening to a few more sentences of reprimand, I went home, feeling pretty sour about paper making in general and Tomahawk Kraft in particular. Ten years later I saw Kermit Olson on the street in Tomahawk, and he asked me if I remembered being called on the carpet for putting starch in the cooking liquor. I did, of course, and then he said: "You know, they've been doing it that way ever since you left!" How glad I was to be working in a place where innovation and creativity were appreciated and rewarded!
This episode, along with the climate extremes and the fact that Caryl had contracted pneumonia prompted me to consider quitting this job and moving to the Northwest. I wrote letters to three paper mills in the Puget Sound area, outlining my laboratory experience, which was really quite limited. I received polite answers, inviting me for job interviews if I moved to the area. I think the rotating shift work schedule was the deciding factor in my decision to quit this job. I was never able to get enough rest, became irritable and hard to live with, and when I told the boss I was quitting, I had no regrets.