Methods of Cleaning Carpets
 
Originally, all carpets were scrubbed by hand, with a brush and detergent.  People could do it themselves or bring them into a cleaning facility.
 
Then the Rotary Shampooer was invented.  This is a machine with a brush that goes around-and-around, scrubbing the carpet.  Shampooing is good because the brush breaks loose the deep down dirt.
 
However, a shampooer has no way to get the dirt and shampoo out of the carpet once it breaks it loose.  So, it leaves it in the carpet.  The shampoo that is left in the carpet acts as a magnet to attract and hold dirt and dust.  As a result, a short time after cleaning the carpet, it becomes dirtier than it was before the cleaning.
 

  The Steam Cleaner was invented to solve the problem of the dirt and soap being left in the carpet.  A steam cleaner is the combination of a pump sprayer and a vacuum cleaner.  The solution is sprayed down into the carpet and vacuumed up. The benefit of steam cleaning is that it actually pulls the dirt out of the carpet.  This machine is also called a soil extractor because it extracts (takes out) the soil (dirt).
 
There are two categories of steam cleaning machines, portables and truck mounts.  Portables, like the name suggests, are small enough to be brought into the home.  They have to be hand filled with hot water from the tap and the water it extracts is drained into buckets and usually flushed down the toilet.  They are less expensive to purchase and maintain and don’t require a gas-guzzling van to haul around.  They are also the only equipment you can use where you can’t get a truck close enough to use a truck mounted unit -- for example, an apartment or office building.  Some of their disadvantages are you have to stop periodically to add clean solution and dump the dirty one.  They are also not as powerful as truck mounts so you usually need to do a treatment to the carpet beforehand to break the dirt loose.  This also adds time to the job.  Also, because the vacuum isn’t as powerful, the job takes longer to dry—an average of about 8 to 24 hours total.
 
The second category of steam cleaner is the truck mount as has been referred to above.  This is a powerful piece of equipment that can cost 10 to 20 times as much as portable equipment.  The equipment and all its attachments fill the inside of an average sized van.  It is best viewed as a cleaning plant.  The technician runs a long hose from the truck into the house and never has to add or dump water during the job.  Because the equipment is bolted to the truck, larger vacuum motors and spray pumps can be used delivering much more power at the point of contact with the carpet.  As a result of the more powerful vacuum action the carpet dries faster than with portable equipment.  They also heat the water well above the level of the average home water heater boosting the cleaning power of the solution.  As a result, you often don’t need to vacuum, spot or scrub before you steam clean it.  A skilled carpet cleaner can get your carpets just as clean with a portable unit, but the job can take longer and the carpets will take longer to dry.
 
Over-Wetting

A problem that has occurred with shampooing and with steam cleaning is Over-Wetting.   Over-wetting can cause odors, shrinkage and mildew.  Some carpets can take up to 2 days to dry without being over-wet if the ventilation is poor or for a variety of other legitimate reasons like a thick pile.  This does not usually cause a problem, and if it does, in almost all cases it can be easily corrected.
 
Over-wetting is when excess solution is left in the carpet that should have been removed.  It is caused by poor or faulty equipment, laziness on the part of the cleaner, inexperience or poor training.  There really is no excuse for over-wetting.  Professionals don't have this problem.
 
Dry Cleaning

Over-wetting is a rare occurrence.  But because of the fear of over-wetting, various forms of dry cleaning became popular during the 1990’s.  There are many different dry cleaning methods available.  Some use a powder, some use a carbonated liquid that dries in about 1½ hours, etc.
 
Dry cleaning is very safe, but it has not achieved the cleaning results of other methods and tends to leave some residue in the carpet.  
 
Summary

As a final important note, no method is a substitute for a skilled technician.  Any method misapplied will not achieve the best results.  On the other hand, a skilled technician can get a good result with a bucket and a brush if that’s all he had.