Clearing snow and ice from marble steps

On behalf of Christopher Gray <methistory [at] aol__com>, Steve
Stokowski writes

>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?
>
>I cross posted Barbara's query on Bullamanka-Pinheads, a listserv
>oriented towards architectural conservation, and Steve Stokowski
><crushstone [at] aol__com made the piquant remarks below (reproduced with
>permission)
>
>   "Apparently she doesn't know as much as she thinks she  knows.
>    Just why shouldn't salt be used on marble steps? No good reason
>    at all, she may have half read and retained less a newspaper
>    article about salt use on roads. The issue with salt, and I am
>    specifically talking about NaCl, is  that it increases the rate
>    of corrosion of steel, specifically steel embedded  in concrete.
>...
>   "So, unless the marble steps are pinned together with ferrous
>    pins, she should go ahead and use NaCl to deice the
>    steps ...

I don't believe that salt should be sprinkled around by the ton.  It
ends up in lawns, in gardens, and in run-off that goes into storm
sewers.  If it's applied to the steps of buildings, it ends up on
floors. The responses I have gotten either suggest more manual
removal of snow before it packs down and turns to ice, or the use of
defrosting liquid that is mostly methanol.

Rather than discuss "piquancy,"  I will say that I want to thank the
thousands of people who log onto the list, bravely admitting their
ignorance on some topic or other, and who then graciously and
generously supply us all with information we couldn't easily get
anywhere else, and all without rancor or snide remarks.

Barbara Appelbaum
Appelbaum and Himmelstein
444 Central Park West
New York, NY  10025
Conservation of Works of Art
212-666-4630


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                  Conservation DistList Instance 23:33
                 Distributed: Wednesday, March 3, 2010
                       Message Id: cdl-23-33-003
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