Breaking ice without destroying the marble


THESE ARE THE times that test our marble, our concrete and our mettle.

Yesterday, as more snowflakes fell, I found myself raging at the flurries and gathering data on deicers, the various melting substances sprinkled on our steps, sidewalks and driveways.

First off, I wanted to know how to remove ice from the marble steps on the front entrance of my house. I'd been told not to put deicer on marble steps. That is what Vincent Migliore, technical adviser of the Marble Institute of America in Phillipsburg, N.J., told me. This admonition was echoed by Joe Althouse, a deicer researcher for the Dow Chemical Co. in Ludington, Mich.

Marble is porous, the men explained. If I used deicer, the steps would absorb the solution of deicer and melted ice. Then, when the temperature dropped below freezing, the solution, now deep inside the steps, would expand and weaken the structure of the stone, they said.

"It works on the stone from the inside out," said Migliore. The deterioration, he said, is gradual and often below the surface of the stone.

Migliore, a stone setter who learned the craft from his father, recommended simply sweeping or scooping -- but never chopping -- the snow off marble steps. That's how he cares for the marble steps outside his own home, he said.

When his marble steps are slippery or covered with ice, Migliore said he sprinkles sand on them to increase traction. (Since sand is messy, you also need to put a mat in your vestibule to prevent the sand from being tracked into your house, he said.) Moreover, if you have marble floor tiles in your vestibule, you should wash them with clear, warm water, to keep the stone in good shape, he said.

"You keep washing them until the water that comes off the marble is as clear as the fresh water in your bucket," he said.

If the sand darkens the marble steps, Migliore said, they can be spruced in the spring with a little sandpaper (he uses 3M Wet and Dry 180 or 120 grit) and some elbow grease. "It will clean the steps right up," Migliore said.

Another good marble cleaner, he said, is pumice, the lightweight volcanic rock. Migliore said whenever he visits Vesuvius, the volcano near Naples, he scoops up a little pumice to take back home.

Migliore had to cut short our conversation on marble maintenance. It was snowing in Phillipsburg yesterday and the time he'd spent clearing off the three inches of new snow had jammed up his work schedule. But he said anyone with additional questions on caring for marble could reach him via e-mail at

Next I tossed questions about deicing my concrete sidewalk and driveway to Althouse, the researcher in Michigan. One of the reasons you want to clear ice and snow off your sidewalks and driveways, Althouse told me, is to remove the pressure on them. This pressure is created by repeated contraction and expansion of water in the concrete during cycles of freezing and thawing. High-quality concrete doesn't absorb water as easily as marble, but the freeze-thaw cycle does put some stress on it, he said.

Deicers, Althouse explained, are stress relievers. When you sprinkle a deicer on your concrete, you cut down on the number of freeze-thaw cycles the concrete has to go through. This cuts down on the pressure on your concrete sidewalks and driveways, and they live longer lives.

These days there is a veritable smorgasbord of stress- reducing deicers to choose from. Among them are the old standby rock salt, or sodium chloride, "hot salts" like calcium chloride and sprays using magnesium chloride.

The difference among deicers seems to be the temperature at which they stop working. In the argot of the snow removal world, this is called the "lowest practical temperature." Calcium chloride, I learned, has a lowest practical temperature of 25 below zero (Fahrenheit). Magnesium chloride works until the temperature hits 5 degrees, and sodium chloride works only until the temperature falls to 20 degrees.

Althouse guided me through the whole maze of deicers but admitted that basically he was a calcium chloride person. That is the type of deicer that the company he works for happens to make.

While singing the praises of calcium chloride, he mentioned that in addition to having an eye-popping lowest practical temperature, it also is "exothermic" -- a scientific term, which, as I understand it, means that this is the Tina Turner of deicers. This stuff is one hot commodity. It gives off heat. "It is an aggressive ice melter," Althouse said.

While rock salt is cheaper than calcium chloride, rock salt is "endothermic." This means things need to warm up a bit before rock salt starts working in earnest.

Yesterday, after the flurries stopped and my conversations with the deicing guys had ended, I resolved to change the way I battle ice.

Recently, trying to remove a stubborn patch of ice, I tossed some deicer on my marble steps. That will not happen again. Migliore, the marble guy, had shamed me into stopping. From now on, I will simply rely on my snow shovel, sand and sunshine. Following the advice of the marble guy, I will also put mats at the front and back doors and instruct members of my family that they are required to wipe their shoes on the mat before entering the house. (Althouse, the calcium chloride guy, also said studies show that the mat method is also a good way to reduce domestic deicer tracking.)

Finally, in an effort to relieve the stress of winter from my sidewalks and driveway, I am going to find some calcium chloride, the hot-body deicer. Who knows, if it snows again, I might rub a little of the stuff on my winter-weary body.

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