Over time spot cleaning just doesn’t do it. You turn around one day and your carpets are a shade darker than when you had them installed. Or, you do a great job spot cleaning only to reveal how dirty the rest of the carpeting really is. Here’s a way to get them green clean.
Therefore, a carpet shampoo must contain a very foamy chemical. The most common ingredient is sodium lauryl sulfate or one of its relatives. Sometime when you’re taking a shower or bath, look at the ingredient statement on your hair shampoo bottle. It will say “Contains sodium lauryl sulfate” or some similar wording. Sodium Lauryl Sulfate and its relatives exhibit a very high and very stable foam and are only fair detergents. The problem is that they dry to a soft, sticky residue which will cause resoiling.
Shampoos are actually very poor detergents and basically simply bury the dirt, they frequently also contain high levels of optical brighteners which take invisible ultraviolet light and convert it to visible light, thus making the carpet appear cleaner and brighter than it really is, for a while. It will eventually give the carpet a yellow cast and the yellow cannot be removed.