The historical record dates the invention of paper to 104 AD, attributing it to T’sai Lun, an official serving at the Chinese imperial court of that time. More realistically, the origins of papermaking would be the result of a serendipitous observation by an unusually bright but unknown peasant, perhaps a silk worker, who noticed a mat of rotted and purified vegetable fibers dried by the sun on a mud bank. This would have been followed by years of patient trial and error, ultimately yielding the procedures which reliably produced paper. T’sai Lun, in his travels, no doubt saw something of these efforts, and was astute enough to recognize paper’s potential. He brought the final developments and subsequent production of paper under the direct control of the imperial court whose records acknowledged his prescience and thus immortalized his name.
From such a beginning, papermaking developed as a skilled craft, slowly adding detail and sophistication, passing down through the generations, fathers to sons and daughters, masters to apprentices. A Chinese secret for hundreds of years, the art of papermaking finally spread along the caravan routes to Arabia, thence across north Africa with the conquering Muslim armies, ultimately arriving in renaissance Europe where it was well ensconced by the time Gutenberg’s invention of moveable type established paper as a product fundamental to a civilized state.
The mechanization and industrialization of papermaking was a product of the 19th century. It was driven by the ravening demand for paper created by the explosive growth of population and prosperity fostered by the maturing industrial revolution. This demand continues to this day with no connection being more secure than the statistical link between the world wide growth in the use of paper and the burgeoning growth of the global gross national product.
This encapsulated history is designed to foster an appreciation for the fact that paper arrived in Europe as an empirical craft with established roots stretching back for more than a thousand years. The transition from a craft to an industrial process during the nineteenth century continued this empirical tradition. Today we can witness the brilliant technical and engineering advances which have reconstructed the craft papermaking process, with amazing fidelity, into a modern industry. The French paper mill clerk, Nicholas Louis Robert, inventor of the Fourdrinier papermachine in 1799, would be impressed but clearly not overwhelmed by the modern version of his original idea. Even the ancient Chinese peasant would see in the individual unit operations of the modern industry, very close correspondence to his own travails. Plotted on some immense graph, the curve of conceptual progress in papermaking would show a generally smooth advance connecting its birth with its current state. No sharp discontinuities would be apparent. The modern industry is unquestionably the product of its history.
Consequences
Modern papermaking is technically sophisticated but scientifically naive. Investment in science by the paper industry is a very recent phenomenon. All the basic technical processes now evident in any pulp or paper mill predated the scientific investigations which have over the past forty or fifty years been dedicated to their explanation. Only in the 1930s was the significance of surface tension and the hydrogen bond, as phenomena fundamental to the existence of paper, fully grasped. Only in the 1950s was the hydrodynamics of papermachine dewatering reasonably elucidated. Only in the 1960s did we really begin to appreciate the rich and complex physics which can account for paper as a product of its fibers.
Science has explained much about why the ancient craft of papermaking and its industrial manifestation actually work. It has contributed immeasurably to the sophistication with which we now manage this process. However, it has had little to do with the fundamental way in which today’s paper is produced. That was determined by the historical processes alluded to earlier.
Modern papermaking is still an art, albeit an engineering art. Unlike the chemical or electronics industries, which are inconceivable in the absence of their scientific base, the papermaking processes predate science, and in this sense are pre-scientific. The scientific investment in the paper industry is designed to service its engineering art, not to question the scientific validity of its fundamental processes. This suggests the interesting question as to what a paper industry might look like if it was created upon the inspiration of science rather than that of history.
Perhaps nothing so strikingly emphasizes the unscientific roots of the industry than the fundamental manner in which it produces its product. A series of processes (cooking, bleaching, refining, forming, pressing, drying, etc.) are employed, each of which represents a unique engineering art designed to impose a constant set of input conditions upon wood or pulp, to transform it by processes which clearly mimic ancient tradition into a material that nature can transform into paper.
Each process is operated essentially independent of every other. The pulp mill produces pulp with a target lignin content as determined by a Kappa or Permanganate number. Screening and cleaning are defined by the operating parameters of the equipment with little additional quality assessment. Bleaching uses brightness, dirt count and viscosity to assess performance, with periodic examination of pulp quality by means of the production and testing of laboratory handsheets. Beating/refining is assessed by freeness. Wet end operation is largely under computer control in respect to basis weight and moisture uniformity with little additional scrutiny.
And finally, at the end of the papermachine, the properties of the paper are assessed empirically by measuring the paper’s response to conditions which seem relevant to customer usage; e.g. burst, tear, fold, tensile, smoothness, porosity, pick, bond, etc. Within any given mill, historical observations correlate such measurements with customer satisfaction and thereafter such measurements become the post facto means for quality assurance to accept or reject the product.
None of these measurements provide any feedback that can be directly and reliably employed by any of the preceding processes, although one or more of them must clearly be responsible for the consequential rejection which consistently undermines the profits of the industry. This lack of any basic theme and the consequent disconnectedness of the formative processes from the ultimate product goal, produces inefficiencies which, although staggering to any outsider, are an integral part of the historical mystique of papermaking. In this manner a typical 20-25% diversion of product to the broke chest becomes part of the normal landscape, and so goes unnoticed.
Possibilities
The one theme which can unite all the processes of the industry with its product is “fibers”. Pulping separates fibers from their rigid location in the biological structure of the wood. Bleaching purifies and whitens these fibers. Refining modifies the surface and internal characteristics of fibers in order that they will properly felt and bond on the papermachine. The papermachine arranges and consolidates the fibers in a layered structure. Natural processes of surface tension and hydrogen bonding, operative at the elevated temperatures in the dryer sections, then securely bond together fibers at points of intimate contact. This transforms a wet assemblage of fibers into the coherent material, paper.
We must look to scientific knowledge of the fibers if we are to realistically endow and recast the processes of pulp and papermaking with a scientific perspective. Pulping should isolate fibers in a manner which ideally enhances and certainly sustains fiber characteristics desirable in the ultimate product. Likewise bleaching should accomplish its mission with similar regard for those fiber characteristics. Refining should specifically develop those fiber characteristics demonstrably needed to achieve product quality. The papermachine should provide the necessary fiber arrangement so that the consolidation and drying processes will transform the potential, created in the fibers by their earlier processing, into the coherent structure which will achieve the properties required by customer usage.
This scientific scenario is essentially absent from the industrial process of papermaking. Which fiber characteristics should be present at every processing stage so that a particular paper product may be produced with maximum efficiency is simply unknown. The actual approach is still dominated by history. The product, or a laboratory manifestation thereof, is made and tested to see if it conforms with predefined standards. If it fails to do so, general experience is used as a guide to making process alterations and the consequences are reassessed in a continuous series of trial and error iterations until a satisfactory result materializes. Frequently, these iterations are driven by the product quality at the reel of the papermachine, with hours of time so distorting the feedback loops to earlier processes that cause and effect connections are blurred beyond rational analysis. This process guarantees the growth of a unique mythology, different in every mill, which sustains the production operation. However, like all such belief systems, the result is a rigid hierarchical mode of operation whose rules of conduct prevent a dynamic evolutionary response to new ideas, and new options.
Scientific Shortcomings
In short, the paper industry operates in a manner which is consistent only with its historical traditions. It has yet to be measured against the yardstick of science. How transforming would be such a revolution? The question is of course purely academic, unless we are prepared to make a genuine scientific assessment and respond to its dictates. The forces of history which have shaped and molded the industry into its present form are a formidable obstacle to such an assessment. These forces have defined the peculiar manner in which science has come to be used by the industry, creating traditions which are inimical to the kind of scientific assessment needed to displace the industry from its current historical track.
As indicated earlier, science is but a recent appendage to the paper industry. In the modern industries whose births were midwifed by science, scientific culture permeates the operation. The interface between research science and industrial operations is difficult to delineate. They grew up together. This is not so in the paper industry. Science was added as an afterthought based on a naive faith that somehow an investment in research scientists would make the industry scientific. The resulting series of rollercoaster ups and downs in the scientific population and budgets of paper industry research establishments which has characterized their short histories is graphic testimony to the tentativeness of their connection to the industrial process. The inevitable consequence of an unintegrated scientific activity is that budgetary frustration will direct it into channels designed to assist in the consolidation of existing processes and subvert effort which does not imply such potential consequences. Under such circumstances a genuine scientific assessment cannot materialize.
While the paper industry has come to accept the desirability of a scientific contribution to its operations, it has been very schizophrenic about the manner of its application. Science has been added as an appendage rather than as an integrated service. Pulp and paper science is largely concentrated in research centers where future oriented questions of process and product are studied. The results of such focus, when successful, become “add ons” to the mill operations: something that can be defined and introduced as a totally controlled “extra”. These are then imposed upon the production operation as something additional and unconnected to current operational habits. When this disconnectedness is viable, the results can be beneficial. When not, the results are frequently disastrous.
The Challenge
The challenge for the paper industry is to change this pattern of scientific application. Science should not be an expensive appendage whose activities are contracted and expanded to meet budgetary constraints. Science should be an integrated partner in the operations at any mill site, whose value is clearly associated with bottom line profits. Science should be primarily a profit-responsible activity and not a budgetary act of faith. This it cannot be until science is as familiar a sight in the practical mill environment as it is in the industry’s research establishments.
This book seeks to present a scientific perspective which can hopefully subvert the historical rigidities which have so persuasively straight-jacketed the scientific contribution to the industry’s economic welfare.
About this Book
The book is presented in two parts. First, a coherent overview of my work in the area of zero and short span tensile analysis is presented. This work makes possible the quantification of the theme which I elaborated earlier, the fiber theme, which unites all the processes of pulp and papermaking. It summarizes from a huge data base of information acquired over the past 25 years, how fibers, as seen through the optics of fiber quality measurements, are altered by pulping, by bleaching, by refining, and by papermachine processing, to yield the final paper at the reel.
The book then turns to the theme of science in the practical world of pulp and papermaking. It presents an overview of my experiences in applying science within this environment. Fiber quality testing is integral to that experience. It provides the necessary integration required to begin to make scientific sense of what the practical processes in the pulp and paper mill can actually do to fibers, how these processes interact, and how they initiate problems which can ultimately surface at the papermachine. Such knowledge is the essential prelude to profitable, science-driven change.
I am hopeful that this “down-to-earth” science will not only prove useful to budding scientists and technologists, but also convey a vision of how science can be made to work more effectively in the pulp and paper mill. In essence, this describes the role of what I have come to call a “mill scientist”. I hope it will give confidence to those scientifically trained mill technical people to persist in their use of scientific vision for problem solving and resist the pressure to indulge in the trial and error, fast fix approach, which so dominates the routines in today’s pulp and paper mills. I would also hope that it will convince their managers to give them the chance to demonstrate their scientific worth.