The surface of brick allows substances such as sidewalk chalk to enter into its tiny pores. Once trapped inside these crevices, the chalk becomes difficult to remove. Wiping the brick with a damp rag does little to remove the chalk stain. The brick requires a cleansing agent along with abrasive action to loosen the chalk and allow it to be released from the brick's surface.
Mix 1 tbsp. mild laundry detergent into a bucket of cold water. Pour the mixture into a pump sprayer.
Wet the chalk marks on the brick with a garden hose. Spray the brick generously with the soap solution.
Moisten a stiff-bristled brush. Scrub the chalk marks with the brush. Wet the brush as needed with soapy water from the pump sprayer.
Rinse the soap and chalk from the brick with the garden hose. If chalk marks remain, repeat the cleaning and rinsing process until they are completely removed.