How do I remove the white chalky substance on my red brick. It cane from the white aluminum siding and it stained the brick. Thanks mike

Many extrerior paints and siding are designed to chaulk over time. They actually shed a thin layer of old dirty paint to expose a new, fresh layer. Unfortunately that chaulk and soak into the brick and get a pretty good hold. Start by trying a pressure washer with jhust plain water. If that doesn't work then work your way up the ladder to heated water and then chemicals like TSP.

OK then start woking up the ladder but do not use any solvents like laquer thinner, that would drive the chaulk deeper into the porous brick.