Maryland Department of Natural Resources

Stop 4: 120 East Redwood Street Building

From the corner of Light and Redwood Streets walk east to the building at 120 East Redwood Street, Stop 4 (currently the location of Metropolitan Health and Fitness). The stone on the exterior of the building is a fine-grained granite. The smaller crystals indicate a faster cooling rate than in the other granites observed previously. This granite has two contrasting finishes: a smoother finish from a multiple point chisel and a rougher finish from a single point chisel (these finishes are referred to in the building-stone trade as a “flat 6 or 8 cut bush hammered finish” and a “rough point finish with a margin draft,” respectively) {Figure 4).

Stop 4
Figure 4

Notice that along the base of the vertical rock panels below the window sills, the stone is spalling, or peeling away (Figure 4). This may be due to physical disintegration by frost action, in which water in fractures in the rock freezes, expands, and wedges the rock apart, or to chemical decomposition in which the minerals in the rock react with atmospheric oxygen and moisture to alter the composition of the rock. Both of these processes may actually be taking place simultaneously; collectively they are termed “weathering.”