The Papermaking Process

The Papermaking Process From the Introduction, The Whatmans and Wove Paper

The process in use in England at the time of the development of the first wove papers, namely, towards the end of the first half of the 18th C., was made up of five basic stages. Only one of these is really relevant to the subject of this book, that is the formation of the sheet at the vat and the subsequent dewatering of the paper. But the other four and closely interdependent stages would have had a bearing on the quality of the finished product and in due course would require adjustment to suit new manufacturing needs; so it is not always possible to divorce the one from the others. As it happened the process had been undergoing a major technological change for several decades and in some paper mills this was still in progress. The main features of this were changes in the method of stock preparation, improvements to the surface of the paper and the method used to construct the laid papermaking mould, all relevant in the present context[2].

Most people today would come across a sheet of paper in its dry and sized state; but its formation takes place in the wet state from a suspension of carefully prepared cellulose fibres in water[3].

The stages which precede and follow this operation are:-

1. The selection of the raw material
During the eighteenth century paper was made from rags. The supply and quality of these tended to be irregular, a mixture of all kinds and varying in degrees of cleanness. White paper, especially White Writing, was the best and was made from furnishes composed almost entirely of linen rags, employing only the whitest of these. As the paper maker of those times had no process available to him for improving their whiteness other than washing the rags in cold water (see stage two), it follows that the ultimate whiteness of the paper was directly dependent on the skill of the rag sorters in selecting the right qualities during the initial stages of the process, a skill that should in no way be underestimated.

2. The conversion of rags into pulp (or "stuff" as it was called)
After sorting, the rags were washed and dismembered in water into their component threads (rag-breaking, one of the most critical phases in the whole papermaking operation) using low consistencies (ratio of stuff to water) and the equipment outlined below. Having achieved this state the consistency was increased and the threads were subdivided into their ultimate fibres, at the same time plasticizing them in readiness for sheet formation (the beating operation).

Mechanical processes were used to achieve these states, processes that had evolved from their most primitive form in which a pestle and mortar had been employed. In Europe the first major advance had been to replace the early methods with a process that used heavy hammers, armed with nails and raised and lowered by means of water power, to pulp the rags[4].

By the time wove paper came into being this technique had been replaced by a revolutionary new method where the rags were reduced to pulp by what was known as a washer/beater, the "Engine", a contrivance that originated in Holland during the seventeenth century[5].

In this Engine the rags, immersed in water, were circulated in an oval and contoured trough by means of a cylindrical roll, furnished with axially oriented metal bars (fly-bars), rotating at high speed and grinding the rags against fixed bars set in a bed-plate, the whole of this plant driven by the paper mill's waterwheel. This was a very skilled operation, only marginally less so than that required for making a sheet of paper by hand.

3. Sheet-making and consolidation
Before this could take place the stuff had to be diluted with further water to a milk-like consistency in readiness for the vatman to make his sheet. He achieved this by separating the fibre from the water, in which it was suspended, using a sieve-like construction, the papermaking mould, which allowed the free water to pass through it leaving the newly formed wet sheet on its wire cover (an operation that is described in greater detail later).

The next phase was to separate the wet sheet from the mould, a function performed by a second member of the vat crew, the coucher, who transferred it onto a woollen cloth by means of a combined rotary and pressing action. Another woollen cloth (the hand felt) was pitched over this, followed by the transference of yet another sheet in a similar manner. This sequence of actions led to a pile of interleaved felts and sheets, known as a post. The sheet at this stage was still very wet and fragile.

The post was taken away and pressed in a screw press to remove as much of the remaining free water as possible. After withdrawal the sheets were in a sufficiently consolidated state to allow a third member of the vat crew (the layer) to separate each sheet (the fibres were now held together by surface tension forces) from the hand felts and lay sheet upon sheet (a pile known as a pack) ready for further pressing (pack-pressing) and then separating again (pack-parting) before being removed to a drying loft. Here the sheets were air-dried. As drying proceeded so inter-cellulose hydrogen bonds were progressively formed to give the dry paper its strength. In this waterleaf state it was an absorbent article unsuitable for use with aqueous media such as ink or watercolour.

4. Sizing
This is an additive process that confers on the paper the ability to bear ink. The traditional practice of immersing the unsized sheet in a tub filled with a hot solution of gelatine to which potash alum had been added was observed in the 18th C. The function of the alum was to fix or cross-link the gelatine to the cellulose sub-strate[6]. Excess gelatine was pressed out and the sheet dried once again in a loft under carefully controlled conditions, first cooling the paper to convert the size from the sol to the gel state; and then either protecting it from exposure to excessive chilling or ensuring that the size did not revert to the sol state as it might have done in very hot weather. This was always a very tricky operation, "le collage du papier manque souvent"[7].

5. Sorting, Finishing and Packing
These activities were performed in the Salle where the felt hairs were removed from the surface of the paper which was then sorted for faults and graded into various qualities, the best being "White Writing" (important to note in the context of this work). Lower grades, but still White, were used for printing and copy papers. Finishing (or Perfecting) generally involved further, dry, pressing; and, in special cases, the paper might have been subjected to a so-called glazing process, which could have taken the form of hammering; slicking with a smooth stone; or the use of a glazing wheel to buff the surface. Not all papers were perfected because hand press printing involved moistening the paper again (a practice that persisted until quite late in the 19th C.) which would have nullified any "finish" given to the sheets. As the paper had been air-dried in this process there was no need to leave it to "mature" for long periods as in more recent times.

The sheets were then counted into quires and reams, the former being folded with defective or broken sheets placed between them, the worst of these being on the outside. The whole was then tied up in wrappers made out of "vat bottoms" and other waste material.

The above is a very much abridged account of the papermaking process, but it should be sufficient for the purpose of this book, placing the sheet-making operation in perspective.
A sheet of paper can, however, be formed in a number of different ways. This is an appropriate point to outline some of these in order to present the first European specimens of wove paper in their proper context.

Footnotes
[2] Balston, J.N. Bib.2 A detailed account of the changes that took place in the making of paper by hand in Britain between the end of the 17th C. and the third and following decades of the 18th, and their impact on the economics of the process, the improved status of the domestic White paper industry and the quality of its products. This work should be consulted, if further information is required beyond the summary account in the text above. (Introduction to both Volumes: and Vol.I Chapters I Part 3; V & VI; Vol.II App.V).

[3] Water is used with or without additives. Other liquids have been used experimentally in order to demonstrate the essential relationship between cellulose/water which imparts strength to a sheet through inter-cellulose hydrogen bonding, a property not conferred on it by other solvents (Bib.2 App.V).

[4] Illustrated accounts may be found in Bib.2 Chap.VI Plates 11, 12; or, more extensively, Le Francois de Lalande, J.J. Bib.8 Pl.IV; Desmarest, N. Bib.27 Pl.III, V.

[5] For a full account of the Engine and mode of operation, including its ability to water-wash rags, see Bib.2 Vol.I Chap.VI and Vol.II App.V.