Clearing snow and ice from marble steps

In response to a comment to the contrary regarding the use of salts
on marble steps for deicing, there is an issue with this. Salts,
particularly anything with NaCl or MgSO4, are one of the leading
contributors to stone decay. Once the salt becomes damp, it begins
dissolving. The salt-laden moisture is then carried through pores
into the stone where it is redeposited. During wet-dry cycles, the
salts themselves cycle between being in solution and crystallising
in the pore spaces. The pressure formed by this crystallisation in
confined spaces causes the stone to crack, leading to granular
disintegration, blistering, spalling, etc. This, in turn, creates
more pathways for moisture and salt to enter the stone. Hello,
vicious cycle.

There is also concern for resulting salt build-up in nearby building
materials (adjacent walls, etc.), especially if they are stone or
contain ferrous metals. To avoid salt-related decay problems, find
another method for resolving the slippery ice conundrum; there are
several methods out there, including vapour-permeable sealants,
methanol-based products, and even simple grit (coarse sand, to aid
with traction).

Lastly, may I redirect you to Andrew Thorn's reply (Conservation
DistList Instance: 23:33 Wednesday, March 3, 2010), which is spot-on
and sound advice.

Kara R. Dotter, BSc, MSc, FGS
Weathering Research Group
School of Geography, Archaeology, and Palaeoecology
Queen's University of Belfast
Belfast BT7 1NN
Northern Ireland, United Kingdom
+44 28 9097 3371


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                  Conservation DistList Instance 23:34
                 Distributed: Thursday, March 11, 2010
                       Message Id: cdl-23-34-006
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