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Subject: Crystallization associated with iron gall ink

Crystallization associated with iron gall ink

From: Jack C. Thompson <tcl>
Date: Monday, July 22, 2002
Deborah Carton <dcarton [at] mfa__org> writes

>I have been examining a watercolor and ink drawing on paper by Jean
>Francois Millet in our collection and have noticed a white
>crystalline formation on the surface of the drawing in the areas of
>the heaviest ink application.  The majority of the ink lines have
>bled, appear warm brown in tonality and have corroded the paper,
>indicating that the ink is iron gall.

I am not conversant with all the elements/compounds which might be
identified with X-ray Fluorescence, but a couple of possibilities do
come to mind.

Test the crystals to determine if gum arabic, quartz or glycerine is

Some recipes call for what I believe to be excessive amounts of gum
arabic, and finely crushed sand was often used as a blotter, to
speed up drying.

If the ink in question had excess gum arabic and was dusted with
sand dust that could be the source of your crystals.

If the ink formulation included wine/vinegar/beer as part of the
liquid which leached tannic acid from whatever source, there would
be glycerine (which resists drying) in the ink and sand would be
even more important as a 'drying' agent.

Jack Thompson
Thompson Conservation Lab
7549 N. Fenwick
Portland, Oregon  97217
503-735-3942  (phone/fax)

                  Conservation DistList Instance 16:8
                 Distributed: Wednesday, July 24, 2002
                        Message Id: cdl-16-8-005
Received on Monday, 22 July, 2002

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