On Montague Street in Brooklyn, New York, workers are up on scaffolds cleaning the old brownstone of the Church of St. Ann and the Holy Trinity. They're also cutting out mortar joints, patching the deteriorated brownstone, and tuckpointing the joints. Since is was laid in the early 1840s, the Connecticut brownstone of St. Ann's Church has had to weather many freeze-thaw cycles. Brownstone, a type of sandstone, is not extremely durable under such conditions. Many of the stone blocks on St. Ann's Church have delaminated over the years. Deterioration has been accelerated by previous tuckpointing operations. High cement content mortars that were used created hard, nonporous mortar joints that restrained stone expansion and forced moisture to evaporate at the edges of the stone, instead of through the joints. Instead of the mortar joints deteriorating, the edges of the expensive cut stonework began to decay. CLEANING THE MASONRY Workers are removing the carbon buildup on St. Ann's Church with a proprietary acidic cleaner. TUCKPOINTING THE JOINTS Before they repoint the mortar joints, the workers remove all the hard tuckpointing mortar from previous repairs. The joints are raked until the off-white original mortar is reached and to a minimum of 3/4-inch depth. To make tuckpointing mortar that is compatible with the original mortar, the restoration team had samples of the original mortar analyzed. The mortar conformed to the standards of a Type N mortar. It contained lime and a uniformly fine, milky white quartz sand.