"Identify the crack with your three-part penetrating dye system. First, spray or paint your penetrating dye over the suspected crack and the surrounding area, then wait 5 minutes. Spray the dye-cleaner on a lint-free cloth and clean all of the dye off of the surface of the block. Once you have all visible traces of dye off, spray a light or "dry" coat of developer over the area, then use compressed air to accelerate the drying. Wait at least 1 minute; the crack will be clearly visible in bright purple, red or blue."
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