Infilling outdoor marble sculpture

Vanessa Wiggin <vanessa [at] artworksconservation__com> writes

>I have been asked to quote on the retreatment of an outdoor
>sculpture made of black and white marble. ...
>
>The losses were previously infilled with an epoxy resin and marble
>dust mixture.  While the result was aesthetically pleasing, the
>infills began to fail almost immediately.  Now two years later,
>almost all the fills have been lost or are pulling away from the
>stone.

There is a wonderful tough, flexible epoxy product on the market
used for boat patches that might work.  It is called FlexSet, by ITW
Philadelphia Resins, available through
<URL:http://www.marinetex.com>

It comes in a double barrel syringe dispenser and is opaque white
when fully mixed.  It may be a little too yellowish for white
marble, so adding titanium dioxide may help.  Adding silica will
also whiten it a bit and thicken it to a sculpt-able paste, but it
still might not be translucent enough.  Its pot life is 15-30
minutes, so you don't have a lot of time to mix in additives, but it
can be done quickly on a plate with a putty knife. I mix them in
while I am combining the two parts to save time.

Also, whatever fill you choose, you should prepare the broken
surface first by dusting off all powdery debris and consolidating
with 5% or 10% Acryloid B-72.  IF this was done the last time,
remove it and try lowering the concentration, as it may have formed
too much of a glossy barrier and not allowed the resin to key into
the stone enough.

FlexSet might not be the best for your application, but it really is
tough enough to withstand flexing or  impact when necessary, so the
opacity may be a necessary trade-off.  However, since stone is
porous and epoxy is not, it may only be a matter of time before
water action begins to loosen this fill as well.  UV exposure will
probably yellow it also.  Hopefully, however, it would last a much
longer time.

Polyesters casting resins can also be used, but I do not know if
they would be more or less resilient to impact and UV light
degradation than epoxies.

Linda S. Roundhill
Art and Antiquities Conservation, LLC
Woodinville, WA
USA


                                  ***
                  Conservation DistList Instance 21:60
                    Distributed: Friday, May 9, 2008
                       Message Id: cdl-21-60-002
                                  ***