Clearing snow and ice from marble steps

Barbara Appelbaum <aandh [at] mindspring__com> writes

>A client of ours has asked about the problem of clearing snow and
>ice from marble steps.  She knows that salt should not be used.  Is
>it possible to apply coatings in advance that will mitigate the
>possible effects of salt, or is there something else--ash or sand,
>perhaps--that is not harmful to marble?

Here is a response to the question about the effects of using salt to
clear snow and ice from marble steps .  This information is based on our
experience over several years with the effects of salt exposure on marble
flooring on cruise ships.  On a number of ships, marble flooring has been
installed near doors that opened directly onto deck areas.  Saltwater is
tracked in regularly by passengers and staff, and also blows in during
inclement weather when the doors are opened.  The saltwater penetrates
into the marble, and dries.  The salt then "attracts" water from the air,
and the resulting osmotic pressure from the continual build-up of water
causes the marble to disintegrate.  The resulting pitting is very
unattractive.

There is a similar phenomenon that has been reported with
naturally-occurring granite in the vicinity of the great Salt Lake in
Utah--granite boulders have been known to actually explode, due to the
continued buildup of salt and the resulting take-up of water, creating
high pressures.

There are commercial treatments for marble and granite that provide
protection against slipping; but they need to be applied regularly, as
they are rather superficial, and are removed by foot traffic.

Grace Wever, Ph.D., Montane Associates


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                  Conservation DistList Instance 23:33
                 Distributed: Wednesday, March 3, 2010
                       Message Id: cdl-23-33-005
                                  ***