Here’s a question my customer has asked and I don’t quite know how to answer. “Every time it rains, a blotchy light-and-dark stain appears on my granite sidewalk. If it stays dry for several weeks, it goes away. What is happening, and can

Most granite is very absorbent, and will soak up a large quantity of water. What your customer is seeing is moisture in the granite, which can take anywhere from several days to several months to dry out. Once the granite dries apply a penetrating sealer. This should help keep the water from passing through the surface of the granite.

TIP You can speed the drying of the granite by placing several fans on the surface. You can also use outdoor heaters to remove most of the moisture.