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Brick by Brick: Slag brick used to retain walls

Brick by Brick: Slag brick used to retain walls

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Brick by Brick: Slag brick used to retain walls
At least six tiers of slag bricks support a narrow front yard in the

Editor's note: The following is one of a series of columns from the Butte Citizens for Preservation and Revitalization.

"Something there is that doesn't love a wall." If Robert Frost had come to Butte, he would have known that the main enemies of outside retaining walls here are the cycles of freezing and thawing, and the long slow pull of gravity. Nonetheless, the walls that help hold up homes and yards on our steep hillsides are part of our unique historic landscape.

Concrete, brick, granite boulders, rough manganese-laden rocks, and cut granite blocks all form walls throughout Butte. But a few surviving slag brick walls speak loudly to our mining heritage.

Slag bricks were first used in England in the 1860s to build road beds, break-waters, and retaining walls. It was natural that such abundant, strong, and cheap material — the waste from smelters — would find use in Butte.

The process of hot casting of slag bricks was invented in Butte by J.E. Gaylord at the Parrott Smelter before 1887. Smelter books of the day described his simple method of pouring hot, molten slag directly into cast-iron or sand-clay molds. The technique was considered an innovation over traditional shaping of partly cooled slag, a more labor-intensive approach.

Standard slag bricks from the Parrott Smelter were 12 x 6 x 6 inches, and weighed 55 pounds. One man could produce about 350 a day, and they were sold at 85 cents to $1 per hundred — less than a penny apiece, but enough to pay the slag worker's wage of about $2.50 per day and still turn a profit. Initial uses included linings for kilns and retorts and for road beds in mine yards, but the bricks were also sold to make residential retaining walls like the one in the 300 block of West Copper Street.

Slag brick walls could be dry laid with little or no mortar. They also had excellent crushing strength and were hardly affected by the weather. Their brittleness was probably their main drawback, but once in a stable position they could — and did — last for decades.

Dick Gibson is secretary and webmaster for Butte Citizens for Preservation and Revitalization. For more information about CPR, visit or stop by the office on Thursdays from 10 a.m. to 2 p.m., 405 W. Park St., Suite 200.


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