Staining marble

I need to replace four pieces of marble on an existing building
(load-bearing masonry-the blocks to be replaced are 10 inches deep
by 16 inches square). They are highly visible--at grade at a window
opening right along a busy sidewalk. Thus far, I have been unable to
match the existing stone, which is a marble that was quarried
locally at the time the building was constructed (the stone is no
longer available from the original quarry). The marble is poor
quality, in that it contains significant amounts of silicates in
distinct bands (primarily tremolite and mica); it is off-white in
color, and the carbonate portions are fine-grained (Danby, Vermont
marble is a decent textural match, though off in color). Although
split-face Indiana limestone is a decent match in both color and
texture (though it obviously lacks the silicate bands and
inclusions), the local historical commission official is reluctant
to accept limestone as a substitute. He has asked that we look into
staining the Danby marble for a closer color match to the existing
stone.

I am wondering if others have had experience (successful or
otherwise) staining stone, and what methods have been used? I am
investigating potassium silicate stains, but doubt they will give
the right effect. I would appreciate benefiting from anyone's
experience, negative as well as positive.

Lorraine Schnabel
Architectural Conservator


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                  Conservation DistList Instance 21:27
                Distributed: Saturday, October 20, 2007
                       Message Id: cdl-21-27-028
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