Carpet manufacturers are almost unanimous. The best way is to use hot water extraction, also called deep steam cleaning. Shaw Industries, Mohawk Carpets, and 3M Scotchgard recommend only hot water extraction. They do not recommend dry cleaning! Why?
A good analogy to cleaning carpet is washing your hair
When you are done your hair is clean, sanitary, excess oil removed, smells fresh, and feels soft to the touch (just like carpet that has been deep steam cleaned)!
Now, would you wash your hair by just putting an absorbent powder on it, rubbing it around, and then vacuuming it? (this is the dry cleaning process)
Would this give you the same results as shampooing your hair? Of course not. This is why the recommended way to clean your carpet is Deep Steam Cleaning!
Deep Steam Cleaning
It is actually hot water extraction, but it steams a lot. A good truck-mount hot water extraction unit forces very hot water into the carpet under high pressure, and then sucks it (and the dirt) out thoroughly. “Deep Steam cleaning,” as it is commonly called, has the following advantages:
The high heat kills bacteria, fungus, mold, and dust mites,
making it the healthiest way to clean carpet.
It doesn’t leave a soapy residue, if it’s done correctly. Detergent residues attract dirt, which will cause your carpet to get dirty much sooner.
The high pressure steam penetrates to base of the fibers, removing deeply embedded dirt.
The strong vacuum system removes 95% of the moisture, leaving
your carpet damp to the touch.
Heat really helps! Above 118 degrees Fahrenheit, every 18 degrees doubles the cleaning power of the cleaning agents. Deep Steam Cleaning is done between 180 and 240 degrees. Therefore, very little cleaning agents are used to clean your carpet. The bottom line is that it’s just the best way to clean your carpet!
Dry Foam: The carpet cleaner applies shampoo to your carpet, allows it to dry, and then, without rinsing, sucks the dried shampoo into a vacuum. Can you imagine applying shampoo to your hair, allowing it to dry, and then removing the shampoo from your head with a vacuum? This method leaves dirty residue in your carpet, which is one reason dry foam is not very effective.
Absorbent pad (bonnet cleaning): This method is similar to dry foam, except that the company sets a large cotton bonnet on your carpet and, with a floor polishing buffer machine, buffs the carpet. The rotating motion causes the bonnet to absorb dirt from your carpet. Again the dirt and shampoo is never rinsed out of your carpet. Absorbent pad or bonnet cleaning is like trying to use a large cotton towel or mat to rub the dirt out of your carpet.Absorbent Powder: The dry-compound method spreads a moist, absorbent powder through the carpet. The powder is allowed to dry and then sucked into a vacuum. This method leaves dry sponge particles at the base of the carpet fiber, and because the carpet is not rinsed, this method is not very effective.