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Fingerprints and dirty underwear

March 17, 2009

Here’s one of my favourite non-sequiturs: the paper trade in England was a late developer because the English wore the wrong kind of underwear. It’s an oversimplification, but it’s true to the extent that any overly simplified explanation for a historical phenomenon is true.

A paper published last week lays out a method for fingerprinting the paper used in official documents, as a way of preventing forgery.

Fingerprinting Blank Paper

Interesting method, and interesting idea, but there’s a much more interesting historical precedent. In theory, all paper made until the late 18th century (and possibly later) could be fingerprinted, not just to the specific manufacturer, but traced to the exact batch it came from, except for the fact that fingerprinting is only useful if you’re going to keep a searchable database, big enough to be useful, but not so big that it simply reproduces an exact copy of the universe. And while it might prevent forgery in the immediate future, this becomes a bit more problematic over time.

In actual fingerprinting of actual fingers, it’s not so simple, either, more a scientific CSI fantasy. But the reality, I think, is more interesting. Sifting through possibly millions of prints is less time-efficient than gumshoe detective work, but we’re obsessed with the notion that fingerprints are foolproof, despite having lessons from the past. Every snowflake is theoretically unique, but what you really need is a shovel.

First, a little paper history.


Paper was originally brought to Europe around the time of the Crusades. The earliest paper in Britain dates to the 13th century, but it didn’t catch on until a few hundred years later, and even then, there wasn’t much of a local trade in it. Parchment and vellum were still the most popular materials for important documents, but paper became increasingly common in the 16th century, and until the introduction of woven paper in the mid-18th century, there was only one way to make the stuff.

Until the development of wood-based types, papers were made from the cellulose fibres of plant materials, processed to remove the lignin; the cheapest source for this was to use rags of linen that had been worn around for a while and become soft and pliable, making your dirty undies a handy resource. In England, wool was the dominant material in clothing, and so linen rags were not as readily available as they would have been elsewhere in Europe; most English paper was imported from France. You could also use hemp rope, old sails, and whatever else you could find that was worth processing, but underwear was probably the easiest.

So you took your dirty French underwear, soaked it to get rid of the skidmarks, and pulped it with some animal glues and gelatine, then set it into a rigid wire mould, which was surrounded by a frame known as a ‘deckle’. The paper was coated to give it a smooth finish, and dried in a hanging room. Paper manufacturers also included, in their wire racks, a watermark to indicate not just the place of manufacture, but because each mill would produce paper of varying quality and size, they watermarked their paper accordingly.

They were made by shaping a wire around a pencil sketch of the desired design, with wire twisted into shape, and then fixed to the wire frame within the deckle. Watermark moulds tended to become worn or distorted through use, and often migrated slightly to the right in the mould (to the left on a sheet) through frequent use. The late David Woodward estimated that watermarks in moulds in daily use would probably have moved at a rate of about one millimetre per month. The watermark mould would then have been re-sewn onto the wires of the paper mould with wire that would leave ‘sewing dots’ on the paper.

Originally, the medieval watermark was intended as the trademark of a mill or papermaker, but because mills produced paper of such varying quality, they became indicators of quality and origin, and a customer might ask for paper by its watermark — that’s where the ‘foolscap’ comes from. While the watermark may be difficult to see without holding a sheet of paper up to the light or viewing it using ultraviolet illumination, it was a feature that was very much consciously acknowledged by an early modern paper user.

The relationship between quality and watermark design led to paper mills mimicking the watermark designs of high-quality paper made by competitors, which meant that mills altered their designs fairly frequently, in order to keep abreast of counterfeiters and pretenders; thus there was a very large quantity of watermarks in use that were similar in design. They also started adding ‘countermarks’, small marks either attached to the watermark or elsewhere on the paper.

So what we’re left with is a quantity of information almost impossible to process, and while in theory, that issue of John Donne can be traced to its exact paper source — down to the day, even — in practice, you’re unlikely to find it. Designs had a long use-life, but moulds didn’t last very long, and given how much they might change over a period of use, matching them up can be difficult. Still, the problems of watermark studies — filigranology — are a nice little parallel to the pre-Google internet, when you had to find the handy little prick in a haystack full of porn.

A pioneering study of European watermarks, Les Filigranes, was published in 1907 by Charles Moise Briquet, who searched a hundred or so European archives and collected more than 60,000 examples of watermarks dating from 1300 to 1600. He included 16,112 of these in his book, though he was unable to publish the remainder – he was completely blind by the time the marks were published. This work was continued by Edward Heawood, librarian with the Royal Geographical Society, whose watermark collection begins with fifteenth-century examples, but concentrates on those from the seventeenth and eighteenth centuries.

These catalogues still represent only a fraction of the watermarks in use in early modern Europe – there could be up to a million different watermarks to choose from.

So this online collection of more than 6,500 images of watermarks is impressive, but how much use is it, really?

Like everyone else, I’m a bit afeared of the collection of biometric data, of the money being poured into the development of techniques that will be used approach everything we do with suspicion, but I do wonder how it would ever be worth anyone’s while? The potential for error seems far greater than the potential for finding anything useful, but the least they could do is throw future archivists, archaeologists and historians a bone, and make the shit traceable.

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