The top portion of this block was sandblasted. Note the sandblasting not just eliminated the hard external layer (still apparent on the lower half), it likewise harmed the inward, milder block. Mark ridicules are proof of sandblasting. Source: WHS - State Historic Preservation Office.

Alert: Never eliminate earth, greenery or shape with high-pressure washing or any sort of high-pressure impacting, for example, sand impacting. On the off chance that you wash your blocks, never permit the water strain to surpass 1000 pounds for each square inch (PSI). Spot the splash wand tip no nearer than 12 creeps from the outside of the block. The utilization of higher-pressure power washing will dissolve the harder surface of your blocks and cause lasting harm.