When most of the chemical reaction is complete, a layer of colored residue with a mildly acidic pH will remain on the surface. This layer must be thoroughly cleaned off with a scrubbing machine and water mixed with detergent so the sealer will bond properly when applied to the surface. Water-based sealers, in particular, have little tolerance for residual acid. Using pH paper or pencils to test the surface pH is a good way to ensure that conditions are right. To the water-and-detergent cleaning mix, add a tablespoon of baking soda per gallon of water to neutralize any remaining acid. Scrub with a buffing machine using soft buffing pads (green or white) or a scrub brush, and pick up the residue with a wet vacuum. Rinse until the water is clear. Allow the floor to dry 1 or 2 days before sealing.