What this exercise has done is to show that the watermark evidence is sufficient of its own in determining format, that familiarity with the patterns of watermarking dated paper should enable the bibliographer to establish format independently of any other evidence—just as, of course, the patterns of watermaking pre-1794 wove paper may.
THE TECHNOLOGY of chemically watermarking paper is considered a trade secret because it is owned and leased solely by the Customark Corporation. When patenting a new process or discovery, companies often protect themselves by listing multiple formulas and a variety of possible materials in a range of different combinations. Therefore, it is impossible to determine with certainty directly from the patents the components and proportions necessary for the chemical watermarking process.
With the Customark chemical watermark process, unmarked paper can be made in advance and stored. When an order is received, the watermark design is produced by stamping the pre-made papers and impregnating them with the patented compound under heat and pressure. While the manufacturer considers the resulting mark to be relatively inert . The marks in naturally aged samples are beginning to disappear into the surrounding paper structure. This phenomenon prompted interest in chemical watermarking and resulted in this investigation into some of the characteristics of modern chemical watermarks for the benefit of conservators.
The “sewing” effect created by the security thread which ‘comes in and out’ of the surface of the paper is obtained thanks to this special process, which transforms the surface of the paper into a delicate transparent veil which covers and highlights the security thread at regular intervals.
This watermark is produced by ‘flat’ technology machines during the making of paper, the contrasts in the hues are created by the different thicknesses of the fibres in the pulp mixture. As compared to a mould-made watermark, the hue contrasts are less rich and evident, however it still remains one of the most widespread and effective means against counterfeiting of value security paper.
For the bibliographer there are two major developments in the production of paper in Britain in the period under consideration which are of immediate relevance. One is the change, resulting from legislation which came into force in 1794, in the location of watermarks within the traditional hand-held mould. The other is the transition from hand-made paper (a process by which paper is produced, one sheet at a time, from hand-held moulds dipped into vats of stuff in suspension in tepid water) to machine-made (a process by which paper is produced by machine in a continuous web, to be cut into sheets of the required size at some subsequent stage).
Make a distinctive impression with your own watermarked papers.
Watermarks are designs or patterns put into the paper when it is made, by making thinner (line or wire watermarks) or thicker (shadow watermarks) adjustments to the layer of pulp when it is wet.
The dilemma for the modern bibliographer is, however, largely resolved by the paper-makers' adherence to the provisions of `An Act for repealing the duties on paper, pasteboard, millboard, scaleboard, and glazed paper; and for granting other duties in lieu thereof, (34 George III, c.20), which came into effect 5 April 1794. Among other things, it provided that British-made paper used for writing, drawing and printing (`first class' paper) was to be taxed at the rate of 2½d. per lb. For present purposes the key provision of the Act was that printed books—whether bound or unbound—were, on export, eligible for a drawback (a refund of part of the duty already paid) amounting to 2d. per lb., with the proviso that `any such printed books . . . shall have visible in the substance thereof a mark commonly called a of a date of the present year of our Lord in the following figures 1794, or in a like manner of some subsequent year of our Lord.'
The high cost, inconvenience, and difficulty of producing intricate designs in conventionally manufactured wire or chiaroscuro watermarks were the impetus behind the invention of a simulated watermark in the commercial papermaking industry. The process of chemically watermarking paper allows for a greater diversity of applications at significantly lower cost. cites the costs and limits a0111s being approximately $300 for a dandy roll with a minimum order of 200,000 papers (400 reams) versus $20 for a chemical watermark pattern and a minimum order of 12,000 papers (24 reams).
The `or' in this provision of the Act of 1794 is ambiguous, with the result, it is sometimes maintained, either that some paper-makers misunderstood the requirement to use the current year or that it allowed them to continue using moulds dated `1794', thus saving themselves the bother of changing the date in their moulds at the beginning of the new year. Indeed, Thomas Balston notes of the Whatman mills, the largest and most highly regarded paper-making concern in the country, that
The watermark `J. Whatman, 1794' is found in so many books and letters of the period 1794-1800, and any other date is so rare, that it seems certain that it continued to be used for some years, a not uncommon procedure in paper making. . . . From that year  the correct date seems to have been employed.
As has already been noted, by the early 1790s much British paper was wove, and often enough without watermarks, thus lacking the traditional indicators of format. Hence the Act of 1794, in requiring the inclusion of a watermark, in the form, at a minimum, of a date, has provided the modern bibliographer with the means of undertaking the analysis of printed volumes, in particular the means of determining format. The Act had the effect of encouraging the migration of all watermarks (now increasingly paper-makers' names or initials) to the edges of the sheet, often accompanying the date. I am not aware, however, that there has been any systematic illustration of the form of watermarks in wove paper from around the turn of the century or their disposition within the sheet. But since a familiarity with the various patterns may be an aid in determining format (or in undertaking other forms of analysis), I have selected a number of examples from the period for illustration here. (It is likely that further patterns will be revealed with the use of a differently constructed sample.)