This necessary step will remove any residual remaining in the carpet fibers and will further rinse on the acid side to prevent the carpet from oxidizing (turning brown), leaving a pleasant scent. Excellent for coffee, tea, and light rust stains. Safe on all carpet fibers including wool. Does not contain any optical brighteners. The new Gemini Surfactant technology delivers a product that neutralizes harsh alkali residues from previous cleanings, removes detergent residues from the fibers and gives the dry carpet a fresh clean feel.