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Subject: Marble plaque

Marble plaque

From: Jonathan Kemp <j.kemp>
Date: Friday, February 9, 2007
Debra-Kay Palmer <debbiepal99 [at] yahoo__co__uk> writes

>I am a Conservation Officer treating a marble plaque, which has lead
>used to fill in the space of the letters. However, some of the
>letters have fallen out and I'm not sure what can be used to replace
>these lead letters. Does anyone have any suggestions about what
>could be used, something that could also survive daily exposure to
>the sun.

I'd like to ask a few questions and make a few points about
potential treatments for replacing the missing lead letters:

    1.  Are the remaining letters generally Flush to the surface of
        the marble, or are they Raised?

        Flush lead lettering is accomplished by carving letters in
        the stone, drilling small splayed holes inside the cut
        letters and hammering lead into the holes/recesses. The lead
        is then trimmed flush with the stone surface using a sharp
        broad chisel.

        Raised lead lettering--The letterform is drawn on the
        surface of the stone, small splayed holes are then drilled
        inside the drawn letter and the lead is then beaten over the
        surface (with a rubber mallet) leaving a thin wafer of lead
        fixed in the angled holes. The letters outline is redrawn
        and the excess lead carefully trimmed off.

        In both cases the holes are drilled at an angle to each
        other so that the pegs are splayed and thus mechanically
        lock the letters in place.

    2.  Before the specification of alternative infill materials I
        would suggest, if at all possible, to replace the missing
        lead letters with new lead letters.

        Lead lettering oxidises slowly. It is the combination of
        workmanship, plaque aspect and the weathering of the marble
        substrate [which is soluble in rain, a naturally weak
        carbonic acid] that has left the lead letters exposed and
        loosened their mechanical key. Replacing the lead letters
        isn't as daunting as it might sound. Done with care, and
        given a reasonably even surface, replacement can be carried
        out without damaging the marble.

        Ethical considerations are:

            *   Renewing extant drillholes: if any extant drillholes
                in the letterforms are eroded they might need to be
                redrilled deeper to take the new letters.

            *   New vs. old letters, where some distinction could be
                made to the finish of the new letters

            *   If, in the case of Flush lead letters, the cut edges
                of each letter in the marble are similarly eroded
                then you might consider the final definition of
                letter shape needs to take place in the careful
                cutting of the lead. Recutting the letter shape in
                the marble before applying the lead should not be
                considered.

    3.  Given that any extant holes in the letters are going to be
        splayed or angled then any cast resin copy will not be
        attached successfully if it incorporates these pegs.

    4.  If replacement is impossible because the stone is too eroded
        and any intervention compromises its integrity then I would
        paint the letterforms on. as suggested by another
        correspondent, but using a mineral rather than enamel paint
        (eg. Keim paint).

Jonathan Kemp
Sculpture Conservation
V&A Museum
Cromwell Road
London SW7 2RL
+44 2079422121


                                  ***
                  Conservation DistList Instance 20:41
                 Distributed: Sunday, February 25, 2007
                       Message Id: cdl-20-41-004
                                  ***
Received on Friday, 9 February, 2007

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