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Archiver > MEMORY-LANE > 2006-01 > 1136143993


From: WJFreeman <>
Subject: Re: [ML] watermarks, papermaking, filigrees, and dandy rolls
Date: Sun, 01 Jan 2006 14:33:13 -0500
References: <c66202f00601010825o3d088509m5532f7d3aa639477@mail.gmail.com>


".... valentine53179" wrote:

> remember when you could hold up fine papers to the light and see the
> name of the paper company...? the finer the paper, the more chance for
> a watermark....

Well, since I worked in the paper industry for close to twenty years, I do
know what a watermark is.

It is found mostly as you say in fine papers and more specifically usually in
printing and writing grades and bond papers. Nowadays, a lot of us buy
reproduction grades of paper for our computer printers so we seldom see the
watermarked fine printing and writing papers anymore. At least I don't.

In the early days of papermaking, there was fierce competition between paper
manufacturers when all paper was made by hand from paper molds. To mark an
individual paper production, a fine set of wires, a filigree, was woven into
or sewn onto the drainage wire in the paper molds.

This produced a slightly raised area where the filigree wires in the screen
were located. This effect can be seen as a lighter shade or different
thickness (caliper, actually) of the paper in the watermarked area when you
hold the paper to the light.

Today, very little paper is made by hand except for some hobby or art type of
production.

And today, paper machines are gigantic things in which the Fourdrinier
process is used almost exclusively. Here a moving wire or screen belt, which
can be very large indeed accepts a very dilute slurry of pulp fibers from a
distribution device called a head box.

As the wire travels at high speeds often foils (airfoil shaped devices) and
suction boxes are position below and touching the moving screen to aid in
removing water. At the end of the drainage section of the wire is a couch
roll which is used to further squeeze the excess water from the continuous
sheet. Usually a dandy roll is located just ahead of the first suction box
and lightly kisses the wet, draining pulp surface. A dandy roll is a light
screen roll and may contain the water mark design. This dandy roll imprints
the watermark on the still quite wet sheet in a continuos process as it
begins its journey on down the paper machine through the couch rolls and into
the drier section. Dandy rolls without watermarks are sometimes used to
smooth the surface (no wire side) of a sheet as well. Nowadays, owing to the
high speed of the machines dandy rolls are power driven so as to impart less
drag and smearing on the surface of the sheet. In older and slower machines
the dandy rolls were turned by the action of the moving sheet itself.

The dandy roll has much the same effect as did the filigree pattern of the
primitive screens used by early papermakers, but is far more practical for
modern high speed paper production.

A filigree pattern would be incredibly expensive to have put into the paper
screen or wire as it is called and would invariably clog and be trouble to
maintain. Also the wire life would be an issue as it is a big expense to
replace a worn wire not to mention the lost production time involved as
well.

And finally, if the paper machine is to make another grade of paper in which
a watermark is not desired and if the pattern were a part of the drainage
wire, the mark would persist where it was not wanted.

With a dandy roll, one can just hydraulically lift the roll from contact and
Voila!, no watermark.

Walter

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