There are all types of professional carpet cleaners using many types of carpet cleaning methods. The most common methods are hot water extraction (steam cleaning), bonnet cleaning, encapsulation and dry powder. By far the most common method is hot water extraction but there are a lot of companies trying to differentiate themselves by using other methods, with varying degrees of success. I will talk in depth about each method because I have personally used each method.
Hot Water Extraction
You might know this method as steam cleaning but a better name for it is hot water extraction. While you might see steam coming from the wands of higher powered cleaning units, the water that is doing the work is under the 212 degree temperature of steam. Steam can not absorb and remove soil, the steam you are seeing is the water cooling as it travels to the ground. Most good truck mounted machines will be working with water temperatures between 180 and 200 degrees. Portable machines can reach similar temperatures if they are equipped with good heaters but they typically can not hold those temperatures, more on that later in my in depth steam cleaning article.
Hot water extraction is the most commonly used method of carpet cleaning for many reasons, mainly because it has the capability to remove the most soil. It is also easier on the fibers because it does not depend on mechanical agitation as much as other methods. These two reasons are why most carpet manufacturers recommend HWE. The only downside to the method is that it has the longest drying times. Dry times are in the neighborhood of 4 to 6 hours if your cleaner uses a truck mounted machine, longer if they use a portable.
How It Works
To start the cleaning, your carpet cleaner should vacuum your carpet. Dry soil removal is key to any cleaning method but many companies tend to skip over this step or rush through it. Because of this, even if your carpet cleaner says that they will vacuum your carpet, you should do it yourself as well. Dry soil is far easier to remove than wet soil. Think about the difference between trying to sweep up sand versus mud. In addition, by removing the easy to get to dry soil, you free the carpet cleaner and the cleaning chemicals they use to work on the tougher soils.
Next, a pre-treatment should be applied to the carpet, preferably hot. The hotter a chemical is, the more active it is. Most cleaners will use a device called an injection sprayer to do this. This is a container with concentrated cleaning solutions. They hook it directly up to their hot water solution line and it allows them to use hot water from their machine to dilute the solution and spray hot cleaning solutions onto your carpet. The solution should be allowed to dwell for at least a few minutes to give them time to break down and absorb soil.
After the solution is given time to work, it is rinsed from the carpet with hot water from the machine. The floor wand will spray water on the floor and immediately extract it, removing the soil and cleaning solution. Some cleaners will use plain water to do this but in my opinion, they are leaving much of the soil behind by doing this. Regular tap water does not absorb as much soil as treated water. At the very least, your carpet cleaner should use softened water which has been treated to remove the minerals and allow it to absorb more soil. Even better is a good rinse aid. This can be a soap free rinse or a low residue detergent rinse. Quality rinse aids leave your carpet nearly residue free so that they do not attract soil and they will remove far more soil than a plain water rinse.
Following the rinse step, some carpet cleaners will groom the carpet with either a carpet rake or a carpet brush. This is very optional in my opinion if your carpet cleaner is using a truck mounted machine. Truck mounted machines have the power to lift the carpet fibers up for proper dring and grooming has little effect. If, however, your carpet cleaner is using a portable machine, grooming the carpet is important and will speed up the drying of the carpet becaa=use it will stand all of the fibers up.
Bonnet cleaning uses absorbent pads on a floor machine to absorb soil. It is considered a dry cleaning method although it does use moisture so a more proper term is low moisture carpet cleaning. The concept is similar to using a rag to clean your countertops. The carpet cleaner will spray a solution on your carpet to absorb the soil and then they will use cotton or synthetic pads on a spinning floor machine to absorb the soil. The floor machine used is typically a slow speed buffing machine spinning at 175 rotations per minute. Some cleaners will use an orbital machine to add a little agitation. Orbital machines spin in a random orbit which increases agitation. Take note, bonnet cleaning and orbital cleaning methods can void some carpet warranties because they can cause tip bloom and fiber distortion. Check your carpet warranty for details.
Bonnet cleaning is most commonly used in commercial applications where the carpet is cleaned often and must dry fast. It is much more limited in the amount of soil that can be removed and is not the best choice for residential carpet cleaning. This is particularly true with carpets affected by pet stains as the carpet pad would absorb the pet urine/feces and could potentially spread it to other areas of the carpet. Most cleaners would use a single pad for a room and the absorbed contaminants are not locked in once absorbed, thus they can be spread around.
How It Works
Just like any other method, dry soil removal with a proper vacuuming is essential. Dry soil is easier to remove and with “dry” methods like bonnet cleaning moisture is limited. You do not want the dry soil in your carpet sucking up all of the moisture, limiting the ability of the cleaning solutions to attack the greasy and oily soil. If possible, vacuum your carpet before your carpet cleaner arrives, just to make sure that as much dry soil is removed as possible.
The next step is the application of a cleaning pre-treatment. The pre-treatment should be a non residual detergent or soap free solution because there is no true rinsing step in this process. The solution is allowed to dwell for a few moments before being extracted with the bonnets or floor pads.
Rinsing involves placing a floor pad or bonnet under a rotating floor machine. The technician will use the pad and machine to agitate the carpet and absorb the soil. Heavily soiled carpets may require multiple pre-treatment and extraction steps. The carpet cleaner should continue cleaning the carpet until the carpet pads or bonnets stop becoming visibly soiled.
Grooming the carpets is the next step in the process. Unlike with steam cleaning, grooming is mandatory with bonnet cleaning. This is because the cleaning process will leave swirl marks and if the cleaner does not groom them out, the marks will remain apparent. Grooming must be done before the carpet dries.
Learn More About Bonnet Carpet Cleaning
Encapsulation is essentially a new spin on carpet shampoo cleaning. The concept behind the process is that a solution is applied to the carpet to absorb the soil. The solution absorbs the soil and then crystalizes, trapping the soil. The solution and the soil is then later removed from the carpet during routine vacuuming.
Encapsulation is another one of those methods that is best used for commercial applications but has been adapted for residential use by some companies. The benefit to the method is that it dries very quickly. The negative is that it does not have a true extraction method. It depends on a later regular vacuuming. For commercial, low cut pile carpet, this is not a problem. The carpet is vacuumed daily in most cases and the crystalized soil is easy to remove. In the residential world, carpet is vacuumed weekly at best and the crystalized soil is hard to remove from deep pile carpet, thus most of the crystalized material is likely to settle to the bottom of the carpet.
How It Works
At this point, I sound like a broken record but dry soil removal is ever so important with “dry” carpet cleaning methods. Dry soil will suck up the limited amount of moisture being used and because there is no aggressive extraction step, it is harder to remove later in the process. Before your carpet cleaner arrives, vacuum your carpet. Even if they say they will vacuum, the more the better.
Like most methods, the next step is the application of a cleaning pre-treatment. With encapsulation, the cleaner is designed to dry to a brittle crystal. It is supposed to dry fast, so limited dwell time will be given. The solution will be applied to the carpet and then almost immediately agitated with a floor machine. Most of the machines will be of the counter rotating brush variety. These machines use cylindrical brushes that spin in opposite directions. These are great because they can dig out soil that is deep in the fiber. If you have pets, you will probably be amazed at the mount of hair that comes out of the carpet. Your carpet cleaner should run the machine in two directions to reach all sides of your carpet fibers
After agitation, the cleaning process is done. Your carpet cleaner will leave the carpet to dry and in theory, the solution has absorbed the soil and will be removed the next time that you vacuum the carpet. No grooming should be required because the cylindrical brush machines will leave your carpet upright and neat.
Dry Powder Cleaning
Like with all “dry” cleaning methods, some moisture is used. Dry powder cleaning however uses the least amount of actual moisture. The powder is moistened with a mild detergent an then applied to the carpet. Your carpet cleaning technician will then agitate the powder multiple directions to break down and absorb soil. When done, they will vacuum the powder out of the carpet, removing it and your soil.
Dry powder cleaning is an acceptable method of carpet cleaning for commercial applications and it does a fair job in the residential world. Because it dries in minutes, commercial facilities that can tolerate no down time will find it ideal. Places like airports and casinos are just the thing. In the residential world, it does have lower soil removal ability compared to Hot Water Extraction but the brushing mechanism of the Host machine allows for greater removal of the soiled cleaning sponges after a cleaning. Still consumers will find that the sponges will remain present in their carpet for some time. They cause no problems or damage but can be a nuisance.
How It Works
As with every other method, dry soil removal is extremely important. This method however shines in dry soil removal. Most cleaners using this method will be using the Host carpet cleaning method. The host machine use counter rotating brushes that literally reach all the way to the base of the carpet. This allows it to remove more dry soil than almost any other method. It also separates the fibers, preparing them for cleaning.
After dry vacuuming, your carpet cleaner will apply the dry powder sponges. The sponges will contain a slight amount of detergent to break down the soil. Heavily soiled conditions may require the addition of an additional pre-treatment spray. The sponges are then immediately agitated with the host machine or another counter rotating brush machine. The technician will agitate in several directions, usually north and south, followed by east to west, This assures that all parts of the carpet fiber are reached.
Once dry, which only takes a few minutes, the powder is then extracted from your carpet along with the soil. Post grooming is not needed with this method as the machine itself does this during the cleaning process. Complete removal of the sponges is not possible but the leftover sponges do not harm your carpet in any way.
Learn More About Dry Powder Carpet Cleaning
Hopefully, the method description methods above have helped you in your decision as to which method to choose for your carpet cleaning. For more detail, take a look at the in depth descriptions linked to at the end of each general description.
For most people, hot water extraction will be the go to method. This is the method that most carpet mills recommend and for good reason. It can remove the most soil and is the easiest on the carpet. Dry cleaning methods depend on agitation to get the job done and this can be tough on the carpet fibers, this is why most mills recommend hot water extraction instead.
If you have lightly soiled residential carpet or a commercial carpet and need to have it dry in a hurry, dry carpet cleaning methods like bonnet, encapsulation and dry powder may be the way to go.
For pet stains and odor removal, the best chance of success will be with hot water extraction.