Solvent-based concrete stains also go by the description "reactive" because the metallic salts in them engage in a chemical reaction with the concrete, according to the Stained Concrete website. Water-based or nonreactive concrete stains simply fill the pores of the concrete with pigment, altering the surface color.
Water-based concrete stains offer a wider range of colors and shades than solvent-based stains, lending themselves to faux surface effects such as marbling more easily than acid-based stains. Acid-based staining tends to create brighter colors that penetrate more deeply into the concrete.
Acid-based concrete stains offer greater permanence than water-based stains because they bond to the concrete beneath the surface level. Both types of stains, however, typically receive an application of clear sealer to protect the result.