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Re: fixative for illumninations



Yehuda,
You're right to advise leaving well enough alone.  The acrylic elements
should contain enough binder to remain flexible until the binder turns dark
and brittle.  Before that happens, it is entirely possible that the acrylic
binder will flow and block to adjacent pages (esp. if the book remains in
Israel's heat); the gouache portions are different, if they are traditional
opaque watercolor, i.e., pigment, gum arabic, and whiting.

The gouache portions may dust off, esp. if built up too much without a
gesso ground.  It may be useful to spray (with an atomizer to produce a
very fine mist) the gouache portions with dilute ox gall.  Not water
colorist's ox gall, but paper marbler's ox gall.

The ox gall can be cut with alcohol to reduce the amount of water absorbed
by the parchment, but unless there is a good reason to do so (the gouache
looks dry and friable, etc.) it would be best to leave well enough alone.
A size made from vellum scraps and applied as a fixative will only create
problems.  At best, the leaves will cockle; at worst, the gouache portions
will cup and fall away from the leaves.  The acrylic portions, once they
are dry, are, more or less hydrophobic so they will not be much affected by
sizing.

You don't mention which ink has been used to hand letter the text.  Some
will do well on parchment and some will not.  Waterproof India ink (which
uses shellac and borax to make it waterproof) will work fine for a few
years.  More years on paper than on genuine parchment; traditional Jewish
ink, with the extra humectant (glycerine) brought in by using Kosher wine
to dissolve the tannic acid from the galls/bark/etc., will likely remain
flexible and attached to the parchment longer than India ink.

Forever?  No.  Longer than we'll be around?  Likely.

Jack

>I have just been commissioned to bind a book which is hand lettered and
>illuminated on parchment (vellum).  The illumination is a mixture of
>acrylic and gouache, and the client is nervous about its durability.  He
>wants to spray it with some sort of fixative, which I have advised against.
>I am inclined to leave well enough alone, but I did promise to ask about
>the possibility of fixing the paintings with something more natural and
>predictable.  I thought of size made from vellum scraps.  Has anyone any
>experience or ideas on this?
>
>Yehuda Miklaf <mfritz@xxxxxxxxxxxxxxxx>

Jack C. Thompson

Thompson Conservation Lab.                    I hear and I forget,
Portland, OR  97217                           I see and I remember,
                                              I do and I understand.
www.teleport.com/~tcl/


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