Carpet shampoo products must have the following characteristics which dictate their ingredients:
- Very high foam levels to reduce wetting.
- Very stable foam.
- High lubricity to reduce damage to the carpet fibers from the brushes.
- Dry to a non-sticky residue.
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.
Because of the resoiling problem, carpet shampoos will frequently also have an anti-resoiling additive such as a resin to reduce this resoiling tendency.
Because 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.
Two primary types of machines are used for this process:
- Cylindrical Foam
- Rotary Shampoo
The Cylindrical Foam Shampoo machine uses an air compressor to create dry foam before the foam is applied to the carpet and the carpet is then agitated with a revolving cylindrical brush which combs the foam through carpet pile. This method will leave dirt trapped in the carpet pile. Carpet must be thoroughly vacuumed before and after cleaning. This is the method used by the Von Schrader machine.
The Rotary Shampoo method uses an ordinary rotary floor machine (the same kind used for stripping wax), sprays shampoo onto the carpet from a dispensing tank and a rotary brush whips the detergent to a foam. Most carpet mills and carpet fiber producers discourage the use of rotary brushes on carpet because of the potential damage that can occur. Overwetting is common with this method which can cause shrinkage and odor.
Shampoo methods are inferior due to poor cleaning plus resoiling problems. The Rotary Shampoo method can damage the carpet, especially cut pile (which is what most residential carpet is).
General Comments on the Methods of Cleaning Carpet:
The choice of the the best carpet cleaning method is extremely important. Some systems leave residues which promote re-soiling and defeat the whole purpose of cleaning. Some methods actually damage the carpet fibers and shorten the life of the carpet. Check with the carpet manufacturer for recommendations.
How Often Should a Carpet be Cleaned?
If carpet is cleaned before it becomes too unsightly, the cleaning chore will be easier and more successful. Allowing the carpet to become overly soiled may result in irreversible damage. It is a common myth that cleaning the carpet before it is absolutely necessary will cause it to get dirty faster. This goes back to the days when the shampoo methods were the most common.
Carpet in a typical household should be professionally cleaned every 12 to 18 months preferably by extraction (steam cleaning) depending upon the number of residents, amount and type of activity and whether the carpet is light or dark color.
Professional Carpet Cleaning versus “Do-It-Yourself” Cleaning:
The maintenance brochure published by the world's largest carpet manufacturer, Shaw Industries, recommends professional carpet cleaning over “Do-It-Yourself” because of the potential problems that can occur from using rental equipment - such as yellowing, overwetting, fiber tip damage, severe resoiling overuse of detergents, etc. Most rental units available do not adequately clean and may actually damage the carpet.