“Da Vinci Code” Style Forensics: Symbols and Secrets Lurking Within the Pages of an Ancient Law Book (Part I)

I was surprised when the staff at the Middle Temple Archives office introduced me to the obscure craft of papermaking, and the hidden signatures that lie within the pages of old books…


The invention of the printing press in the middle 1400’s may have “unlocked the door” to the information age, but it was decidedly NOT flung open.  It required the long, slow process of building the components of the publishing industry and markets to pry that lumbering retardment from its casings! One of the key advancements of the printing industry was the evolution of high quality, stable paper suitable for use in the printing press.  What I didn’t begin to grasp until last year’s visit to the Middle Temple Archives office (in the historic Temple area of London), was the tradecraft nature of early paper making. Creating the paper upon which now-ancient tomes were printed was a complicated, delicate and proprietary process. And these proud craftsmen found a way to imbed secret images into the very fabric of the sheet, investing the paper stock with a “watermark” signature of its creator.

A reference recommended by the Middle Temple Archives Office – which I’ve recently added to my collection!

For about the first 500 years of the paper making industry, paper was made of cloth fibers (not wood pulp) and was created in a “laid” screen process, which left a subtle telltale image of the screen mould the paper was made with in the form of slight thickness variances in the paper.

Papermaking screens (known as a “mould and deckle”) were dipped in a warm slurry of pulp fibers suspended in water.  When this large rectangular screen was lifted flat upwards from the vat, the water would run through the screen, leaving a mat of paper fibers behind.  The mould screen was itself was formed of a wooden frame strung with tight parallel rows of brass “laid” wire passing through opposing (vertical) “chain” wires which helped them form a flat, porus sheet. An illustration of a mould and deckle appears below, as borrowed from an excellent article on papermaking from the University of Iowa (http://paper.lib.uiowa.edu/european.php).

In the early 1800s, a new woven screen process took over, producing “wove” paper (which did not have the distinctive watermark pattern left by the earlier laid and chain wires). About this same time paper made from wood pulp came into common use, displacing the earlier cloth fiber based paper.

When construction of the screen mould was completed, ancient craftsmen would often create specific “signature” symbols from the same fine wire. These were sewn to the screen, knowing that the paper created would be slightly thinner directly atop the wire of the symbol.  The image created within the paper from these subtle variations of thickness can be seen when holding the finished page up to the light.

In this way, this craftman’s paper carried its maker’s hidden mark into every book published upon it.  Furthermore, because each screen was hand crafted, and multiple screen moulds were used in a single paper manufacturing flow, it is possible to definitively identify sheets made from the same specific screen mould.

Fig 16 Mouldmaking
Drawing of a wire screen frame for making “laid” paper, which was used until the early 1800s when “wove” paper largely replaced it. Credit: http://paper.lib.uiowa.edu/european.php

Basics of page layout: creating an “imposition” of pages on a large sheet

The basic wooden Gutenberg printing press design was used from its invention (in the middle 1400’s) until the late 1800s, when the industry briefly transitioned to a metal version of the same basic design. Shortly after, the new industrial cylinder-based press design emerged, quickly relegating the traditional press to niche status.  The size of the sheet frame of the press is determined by the standard paper making screen sizes.

Regarding paper sizes, I found a helpful “Art of the Book” blog article on early common paper sizes that provides the following sheet dimensions and trade names of the early papermaking industry:

· Imperial (30 in. by 22 in.)
· Royal (25 in. by 20 in.)
· Demy (22 ½ in. by 17 ½ in.)
· Crown, cr (20 in. by 15 in.)
· Foolscap, fcp (17 in. by 13 ½ in.)
· Pott (15 in. by 12 ½ in.)

I realize I’ve not spent much time thinking about how a printed book is actually made. The process works so well, most of us rarely encounter a book that isn’t fully intact, with its construction details obfuscated!

The making of a book

Contrary to my early imaginings, successive sections of a book are generally printed on one larger sheet, and folded up (origami like) into the form of book-sized group of pages. These sections of the book are stacked one atop the other, and essentially tied together into a block, bound together on one side.  Then, the binder chops off the edges to free the individual pages (and to provide a uniform edge to the pages) before attaching the spine and covers.  Viola! You have a book.


1600’s printing press on display in the Museum of London

Based on the size of the book and assuming use of standard large printing press sheet size, “Lane’s Reports” may have been printed in a 4×2 “imposition” (layout).  To create this imposition, the printer sets down the words of each page into a page-sized region of the typeset bed, populating each with a field of tightly packed metal characters and print elements fitted together to form the printing surface.

When this typeset bed is fixed in the press, the printer wipes ink onto the faces of the typset pages, and a sheet of paper is mounted into the articulating frame above it.  This assembly holds the page firmly, and folds down to set that page unwaveringly onto the inked typeset bed.  This whole assembly is then slid under the press, which is lowered, tightly pressing the paper onto the type bed beneath it.  As can be seen in the next image, this is done with sufficient pressure to emboss a clear physical impression of the metal typefaces into the paper.

A close up of the Table of cases showing the structure of the paper and the embossings created by the typefaces in the original printing presses.

After making a single test print, the test sheet would be proof-read, and any errors corrected. This process is repeated until it yields an error-free copy of those 8 pages of text.  Then a printing run for that side of the sheet is commenced. All this time, the next typeset bed (for the next 8 pages of content) is being prepared nearby.  When the printing run of the first side is completed, the next typeset bed is loaded, and the process is repeated, printing the backside of the sheets printed in the first print run.

At the end of this “second pass” the printer would have created a single stack of printed sheets, representing 16 pages of text.  If your book had content enough to fill 160 pages, then a full printing of the book would require 10 such dual print runs, each printing front and back of a different 16-page increment of the book.

But how you orient the typeset pages on this printing bed is important! Imagine printing both sides of a single sheet of paper, as shown in the diagram below.  In the folding process, some pages must be typeset upside down relative to others so that they wind up correctly oriented after folding.

This helpful “Art of the Book”  blog article on historic printing processes provides a great description (and industry terminology) of how sheets of printed paper become components of a book:

A sheet, when folded, has twice as many pages as leaves, for the obvious reason that it is printed on both sides, the number of leaves depending on the size of the original sheet and the way in which it is folded.

When two leaves (four pages when printed on both sides) were printed on a sheet so that it could be folded once, collated with other folded sheets and bound, the format of the volume was a “folio“. When four leaves (eight pages) were printed on the same size sheet, which would later be folded twice, the format of the resultant volume was a “quarto” (four leaves). The term “octavo” relates to the sheet having eight leaves printed on it. The octavo is the most general size of a book, and the printed text is so arranged that, when the sheet is folded, the sixteen pages follow consecutively. This folded printed sheet of leaves prior to binding is called a gathering. After binding it is referred to as a signature.

The following diagram shows how a fully printed sheet is folded to become an “octavo” of 8 leaves.

I found this excellent diagram of a 16 page imposition on the printpap.com site.

If you want to try this at home, its kind of fun!  If you write a sentence with each word in the space of its corresponding numeral as shown (black letters on one side, and grey letters on the backside), you can fold the page up to form a small book section, or “gather”.  Note that the folding sequence is important and the two diagrams I’ve provided are not quite consistent to make you think about it just a little (hint: while folding make sure that “1”word is always on visible and right side up) and you’ll have it made)!  Your last step will be to trim away the folds along the 3 non-binding sides of the book to free all the pages.

Diagram of imposition layout for a 4×2 layout (credit to http://www.cuk.ch/articles/2449)

Since Lane’s Reports includes a total of 124 printed pages of  content (62 physical pages, or leaves), it required exactly 7.5 of these 4×2 imposition printed sheets of paper to publish. This this implies that a half-size press frame was available, or that one of the sheets was typeset with two identical half sheets of content.

If 1,000 copies of the book were to be produced, when an ideal print run was completed the printer would have had 7 stacks of 1,000 sheets, printed on both sides, plus an 8th stack of only 500 such sheets.  These stacks would then have been wrapped, loaded and sent to the binder.

Forensic Analysis of an Ancient Book

I’ve gone into all of the previous background for a reason.  Once I came to understand more about the details of the early printing and bookbinding trades, I realized there is a great deal that can be learned from the construction of a book from this period.

Like any other ancient artifact, books cannot always be taken at face value.  A book in good condition may have been repaired, restored, or in some cases, forged. The same knowledge and techniques used to establish the provenance of such books are also important tools for the historical researcher.  For instance, when I initially studied the two copies of Lane’s Reports in the Middle Temple collection, I noted that the two books were not the same height.  At first, I wondered if there had been multiple versions of the book printed, but I was soon informed that the shorter of these two books had been restored.

In that process, the book had been disassembled, and the edges of the pages had been cut back to get rid of the darkened, brittle and uneven edges of the pages, restoring a clean and healthy edge.  Clearly, more had been taken from the top and bottom than the side edge of the pages. This cropping narrowed the margins noticeably, so the text lies noticeably nearer the edge of the page. The cover was similarly cut back and restored to match the pages, with new lettering created to restore the title on the spine. Finally, new endpages were added to renew the attachment of the covers.

The newer paper used for the endpieces was easily identified by putting a light behind it. “Laid” paper printed before the 1800s always has the telltale watermark lines from the wires of the mould it was created from. Unlike the rest of the book, these endpieces had a very even appearance when backlit. They were clearly “wove” (post 1800) paper.

Comparison of the internal artifacts of “laid” vs “wove” made papers

Although a higher-quality restoration would attempt to use authentic period paper whenever possible, such paper is quite rare.  Instead, paper which is old and similar in appearance may be used. In more economical restorations, the best matching modern paper is used.  A favorite trick of restorers is to remove any blank original pages from books being restored so that the purloined pages be used as “raw material” for future book restorations.

My trusty sidekick (my Mom) during the 2017 visit to the Middle Temple Archives. She is comparing their two copies of “Lane’s Reports”, with the restored copy in front of her. Note how close the text is to the top edge of the page (due to cropping).

All of the described restorations of the Middle Temple book were done in a manner that retained its “old” character, but yielded a book in much better condition. The book is so stable it is kept on the shelves of their normal collection library. By contrast, the unrestored sibling copy of Lane’s Reports was in a state of partial disintegration, with even the most careful handling causing it to shed a layer of minute brown fragments onto the examination pillow.  This copy is normally stored in their climate and light controlled delicate storage room.

During last year’s visit to the Middle Temple Archives, it was suggested that I examine my own copy of Lane’s Reports when I returned home.  When I did so, I discovered the endpiece attached to the inside of each cover (forming the first and last “pages” of the book) were made of “wove” paper – and were therefore not original.  Every other sheet in the book was original though, including the covers. I also noted that my copy does not have extra blank pages at the front of the book. Apparently, my book has undergone a minor repair to re-attach the covers at some point, and when it was done, it appears blank pages were removed.  This was not done recently, however, as these new endpieces show clear signs of aging, and required me to call in a restorer to add a bit of reinforcement to arrest splitting (which had begun again).  It is possible that this single detectable repair was itself antique – possibly performed when the book was nearer its 200th birthday than its current 360th.


In the upcoming Part II of this article, we will examine the craftsman’s watermarks in my copy of Lane’s Reports, and compare them to a set provided by the Archives Office of Middle Temple on their (restored) copy.  I’m taking it a bit further, too. Although it is probable that someone else has already thought to “fingerprint” the sheets within a book to the specific screen mould each was produced from, I haven’t run across it yet.  I believe it can be done, and am attempting to prove it, so stand by!

Apparently I am a hopeless nerd, because I find this analysis simply fascinating!


Your comments and corrections are gladly welcomed.  I admire great writing, but have little choice but to approach this task as one of grinding a workable edge onto a rough blade – with my thanks for your generosity of spirit and firm critique in the meantime! 

-Greg Sherwood

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