Chicago brick

The story starts underground, in a blue clay high in lime and iron and littered with pebbles and other glacial debris.

Fired in a kiln, that clay turns colors from dusky yellow to pale pink and comes out speckled with the bits of debris that were embedded in it, so the color comes from the clay itself. The Encyclopedia of Chicago records that by the beginning of the 1890s the metropolitan area had about 60 brickyards making about 600 million bricks a year, that the yards transformed clay abundant in local soils into brick, and that the walls of thousands of local buildings stood as evidence of the industry.

Those figures are history, not a trade number, and no cleaning or sealing rule follows from them. The kiln colors, dusky yellow to pale pink, belong to the fired clay. The color lines in the paver sealing documents, such as those behind do dark pavers need sealing, are written for concrete pavers, not for reclaimed clay.

Chicago common brick was the back-of-building brick, not the face brick on the street front.

It went on side and rear facades, and inside buildings for foundations, chimney flues and structural walls. The last Chicago common brickyard closed in 1981. With the yards gone, no manufacturer remains to publish a cleaning or sealing line for this brick, and what that means for a patio is argued at should Chicago brick be sealed the same way as other pavers.

The name describes the brick, not the way it is laid. A laying pattern such as herringbone is a separate term, and it says nothing about whether the units are reclaimed clay.

The Chicago brick sold today is reclaimed.

When old buildings are torn down in Chicago, the bricks are salvaged, cleaned and resold, prized for a character weathered on buildings for decades or more than a century. As fired clay, it is clay brick in the Brick Industry Association's sense, and how clay brick differs from concrete pavers and travertine in the published guidance is set out in the materials section of the paver cleaning page, and whether clay brick pavements take a coating at all is taken up at can brick pavers be sealed.

Whether a given patio is reclaimed Chicago common brick, another clay brick or a concrete unit made to look like brick is a question for the installer or supplier, and telling clay from concrete is taken up at can clay brick be cleaned like concrete pavers. Chicago, in the name, is where the brick came from.