Ammonia, Detergent and Oxygen Bleach
Mix 1 liter of water with 4 tbsp. of household ammonia, 1 tsp. of liquid dish detergent and 1 tbsp. of oxygen bleach. Oxygen bleach is not chlorinated, so it is safe to combine with ammonia. The ammonia will release the stain, the dish detergent will foam, lifting oil and grease, and the bleach will lighten the stain.
Use a whisk to stir the mixture until frothy. Pour the mixture into a spray bottle. Spray the cleaner on stains and traffic areas, and agitate with the scrub brush. Blot the stain with a clean white towel. Repeat the process if the towel still brings up color from the stain.
Use the solution in your carpet cleaner tank. The cleaner will remove discolored spots and brighten the carpet. The ammonia smell will dissipate, leaving the carpet fresh and clean.
Dish Soap, Vinegar, Ammonia and Water
Pour 3 tablespoons of liquid dish washing soap into the bowl. Add 1 teaspoon of white distilled vinegar, 1/2 teaspoon of ammonia and 3/4 cup of water. The vinegar will increase the cleaning properties of the other ingredients. It has acetic acid, which is useful breaking apart stains.
Whisk the mix until it gets foamy. Spread the foam on a stain or traffic area and agitate it with a brush. Blot the stain with a clean towel to pull up the dirt and color. Put the mixture on a traffic area and scrub. The carpet will brighten up and the pile will raise again.
Pour the mix into a spray bottle instead of agitating it with the whisk to make foam. You can use it as a liquid or shake the bottle and squeeze out foam for use on small areas of carpet. The foam works great on stairs and on car interiors.