Reason: If the stain is not fizzing it may signify an unsuccessful chemical reaction. Stain reacts with lime and other latents within concrete substrate. When a reaction does not occur it could signify that the concrete may be too old, washed out and/or chemical residue or oils may be interfering and preventing a proper reaction. If the stain is pooling on top of the substrate, a sealer or other curing agent may still be on the concrete preventing penetration.
Solution: Make sure any chemicals on the concrete are removed. If the concrete is old or washed out or you are dealing with a very tight power trowel, it may help to add no more than one cup of muriatic acid to one gallon of Chemical Stain Note: do not add muriatic acid to turquoise; doing so will cause an unfavorable result.