For centuries, poultices have proven invaluable for removing stains and contaminants from bricks, stone and mortar surfaces. These days, poultices are often used to draw nasty road salts out of masonry surfaces – a strategy that saves old bricks, stone and mortar in-situ, says Sam Trigila, president Clifford Restoration Limited.
correspondent
TORONTO
For centuries, poultices have proven invaluable for removing stains and contaminants from bricks, stone and mortar surfaces. These days, poultices are often used to draw nasty road salts out of masonry surfaces – a strategy that saves old bricks, stone and mortar in-situ, says Sam Trigila, president Clifford Restoration Limited.
Clifford Restoration put poultices to work recently on a brick and stone fence at the historic property of The Cathedral Church of St. James. The fence had originally enclosed the church but many sections are long gone. A section that remains of the fence or wall was in poor condition, damaged by road salts splashed by passing traffic over the years, says Trigila.
The poultices used consist of diatomaceous earth (a clean and powdery soil) mixed with chopped newspaper-like cellulose and water to form a mud pack applied to the surface for up to a week, or until it dries and falls off.
Trigila says the wall was then tested for salt content to determine if further poultices were required.
It is not uncommon to have to apply three to four applications to complete the process, he points out.
A case in point is another job Clifford Restoration did when Toronto’s old downtown post office was being remade into the Air Canada Centre in the 1990s. There, the contractor applied about 12,000 square feet of poultices on the building’s elevation facing the Gardiner Expressway, a major source of road salt spray.
Some sections of the old post office wall took up to five poultice applications to remove all the salt, Trigila says.
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