The right repointing technique ensures the work will last. At the Rogers house, John Machnicki takes chisel and hammer and starts raking the joints clean to a depth of 1 inch. He takes care not to break the brick's hard fire-skin, which protects the relatively soft core. Chiseling is tedious, painstaking and, for cement-covered joints, frustratingly slow. It's easy to see why repointing by hand costs as much as $25 a square foot. Using an electric grinder with a diamond-tipped blade can cut the cost to $5 per square foot, as long as the joints are more than 1/2 inch wide. But grinders must be handled with skill and restraint — on horizontal joints only, never on vertical — because these powerful tools are notorious for damaging brick. The Machnickis won't use them at all when restoring historic buildings. Homeowners who try to save money by tuck-pointing (patching new mortar over old without chiseling) are throwing their money away, Mario Machnicki says. At best, tuck-pointing leaves a weak connection between old and new mortar layers; at worst, it makes joints wider and more susceptible to water infiltration. When John Machnicki finishes hand-chiseling, he squares the cut and cleans dust out of the joints with a compressor-powered pneumatic chisel. "The mortar bonds better to the clean, chiseled surface of the brick," his brother says. Mortar can't bond to paint or wood so, between brick and window casings, he leaves a gap to be filled later with caulk. "That's a housepainter's job, not a mason's." Before the younger Machnicki refills a joint, he mists the wall with water to keep the mortar from drying too quickly. Then he scoops a glob of the sticky gray mix out of a bucket and onto his plasterer's hawk. Holding the hawk up to the wall, he scrapes fresh mortar into the joint with a narrow tuck-pointing trowel. He doesn't fill the fresh mortar into the joint in one pass. Instead, he makes three to four passes, each time pressing in a thin layer of mortar. When it becomes thumbprint-firm, anywhere from 30 minutes to 24 hours later, he cuts off any protrusions with a pointing trowel. A few whacks with the bristle end of a stiff brush, and the joints match the weathered look of the originals. When finished, the new patches at the Rogers house are undetectable. As always, both Machnickis are proud of that, although it once caused them some trouble. Mario Machnicki recalls: "We sent a bill to a customer after one repointing job, and he complained, 'You haven't even done the work yet!'"