The Right Mix
Before the 1930s, most masons used a lime putty mortar that takes a long time to dry and harden. By contrast, modern-day mortar is harder, quick-drying and cement-based.
Before the 1930s, most masons used a lime putty mortar that takes a long time to dry and harden. The most common reason for using this softer mortar, which contains limestone that is heated and mixed with sand, is to allow buildings the flexibility to bend in the wind. Softer bricks and mortar also allow for the expansion and contraction of a building in extreme temperatures.
By contrast, modern-day mortar is harder, quick-drying and cement-based. The change in construction materials and techniques generally grew out of a need to build bigger and faster, says John Milander, director of product standards and technology for the Portland Cement Association, based in Skokie, Ill.
Fifth-generation mason John Speweik used to use these new materials on buildings that were built with lime putty mortar. Then he noticed that his work on monuments and other historic structures was cracking after a short time.
Speweik soon learned that restoring old buildings meant analyzing the composition of their brick and mortar, and then trying to match it. This meant identifying the size, shape and color of the grains of sand that were in the mix. And from there, an idea to offer this service to remodelers and contractors grew.
Five years ago, Speweik teamed with Mario Machnicki to found the Chicago-based U.S. Heritage Group, a consulting and training business devoted to masonry education. The business conducts workshops for those interested in the preservation business. It also includes a mortar-matching service where contractors can send a sample of mortar and bricks and receive a custom-made batch of matching mortar for about $30 a bucket. For more information, call 773/286-2100 or visit www.usheritage.com.