Wrought iron carpet tack

A Tale of Two Materials

I have been hoping to find a suitable problem full of complexity,
laced with doubt, to be sprinkled with a taste of ethical dilemma to
post to this list. Something dramatic, to be sure, to solicit
discussion and comment between the perspectives of different
conservation specialties. As is often the case, it arrived in my lab
several days ago (Look out. Sometimes you may just get what you wish
for!).

The Problem:

The object is a component of one of our original 18th century
buildings, an architectural fragment, and it was sent to me by our
Architectural Collections Manager with the usual note, "Please
Conserve".  The object is a wrought iron carpet tack which was
pulled from the floorboard of a room with late 18th century
architectural detailing (possibly 1780's).

The problem became complex because I discovered, upon initial
examination, that there were original fiber remnants underneath the
tack-head with intact warp-and-weft structure in situ.  The iron
oxides had migrated into the fibers and had cemented this tiny
textile fragment in place.  How this survived the jaws of the steel
hammer-claw from its removal is a miracle.

The wrought iron tack is extremely deteriorated with severe
corrosion, localized cells of weeping corrosion, adherent
mineralized wood, and severe localized loss of over half of it's
thickness in the middle of the shank.  I am told that this tack is
of great interest to our architects because so very few examples of
them survive.  Immediate and aggressive intervention seems to be
warranted if the tack is to be stabilized and, depending on chloride
testing and corrosion product analysis, I may have to treat it as an
archaeological fragment in order to fully stabilize it.

The fibers are extremely brittle,  shedding with the lightest touch,
and have mineralized iron oxide concretions and soil products
leached into them. Today we took samples and have identified the
fibers under polarized light microscopy as hemp (cannibis
sativa)--no jokes please!  There is the distinct possibility that
this may be the fragment of an oil cloth, so we might have paint in
the top layers of the fiber fragment which is firmly cemented by
corrosion products underneath the head of the tack.

A Conservation Approach?

My immediate inclination is that preserving the fiber in situ is the
least viable option, although the most ethically desirable.  I feel
that to successfully preserve both materials I have to separate them
and conduct separate treatment protocols.  The fibers are too
fragile to attempt to remove without consolidation and, indeed, I am
of a similar mindset in considering treating the fibers as I would a
deteriorated archaeological find.

Before attempting anything I am seeking advice from all
knowledgeable colleagues who may have been presented with similar
dilemmas.

I am very conversant with the treatment options regarding
deteriorated ferrous metals but I am truly in need of counsel in
regards to deteriorated textile treatment options and protocols.

I encourage responses to the list rather than personally as such a discussion
might provoke a point-counterpoint commentary which I would find
illuminating. Cheers,

David Harvey
Associate Conservator of Metals & Arms
The Colonial Williamsburg Foundation
P.O. Box 1776
Williamsburg, Virginia  23187-1776  USA
757-220-7039

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                  Conservation DistList Instance 10:49
                Distributed: Thursday, November 21, 1996
                       Message Id: cdl-10-49-013
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