Cleaning and neutralizing the stained residue remains the most important step to finishing an acid stained surface.

When Chemstain is applied to concrete it reacts with the calcium hydroxide. Once that reaction is complete, there's a residue on the surface that must be removed before sealing. (Mopping the surface is not an effective way to remove the residue because you spread contaminated water each time you return the mop to the surface.)

Before removing the residue, make sure the surface is completely dry. Wait a minimum of six hours after applying the stain.

The best way to remove the residue is with a swing buffing machine with a white pad. After running the bugger over the surface, sweep up or vacuum the dry residue to remove it.

Then neutralize it with a neutral cleaner like baking soda. Ammonia also works as a neutralizer. SC Johnson makes neutral packs that you drop in water to clean the residue.