What’s in a Name?
While there have been some attempts to create a working approach to describe low moisture cleaning, we still don’t have a technical definition currently available which adequately describes the term in a manner cleaners can implement with desirable and repeatable results. Some of the important considerations for describing the approach are:
- Reduction or prevention of potential wicking
- Reduction of microbial growth potential
- Reduction of slip-and-fall accident potential
- Insurance of dimensional stability and prevention of shrinkage
- Reduction or elimination of the drying time to hasten “return to service”
- Conservation of water and energy.
While these considerations may be all concurrently present in some cleaning situations, a cleaning technician may only have one potential issue present, which would lead that technician to control or lessen the amount of moisture in order to avoid any of the relevant negative concerns.
Pursuing the benefits, the technician will use a technique, which modifies a convenient method, or the technician may choose to use a method that already incorporates reduced and controlled wetting to clean with an adequate margin of success.
What about cleaning methods
One could assume that low moisture is inherent in certain methods of cleaning. For example, encapsulation, absorbent pad, dry foam and dry compound extraction typically represent low-moisture methods. There should be no debate that using these methods can bring about desired results.
Dry compound typically is considered the “driest” method. Makers of cellulosic floorcoverings, among others, recommend using dry compound extraction. When any other method is used on these textile floorcoverings, it is common for them to shrink or become dimensionally unstable. Yet dry compound does have water that has been absorbed into its solids, and a severe over-application of cleaning compound could potentially cause dimensional instability or shrinkage of cellulosic carpet and rugs.
Meanwhile, many skilled cleaning technicians successfully use hot water extraction to clean these types of floorcoverings without such problems as shrinkage or ripples, despite being considered the wettest of all methods. The IICRC has said in the past that cleaning results are more affected by the technician than the method.
What about shortening drying times?
If describing low moisture according to cleaning methods has problems, then why not define it by drying times? This will not work either. A shorter drying time is inherent in all of these considerations, but there is no research data that can say that a specified drying interval (e.g., two hour or less drying time) will ensure a desired result. After carpet has been cleaned, the IICRC says drying times are affected by:
The science of drying involves psychrometry, and it is a complex study, meaning one could still have all the problems associated with overwetting and yet have met an arbitrarily chosen drying time.
Shortening of drying time is but one facet of low moisture cleaning, but is not nearly the extent of its definition. One cannot take an arbitrary number created without real science and hold it up as a legitimate augment of low moisture. It simply will not hold up in matters of litigation or court, especially when one shows it did not meet the intended expectations. Without consideration for maintaining carpet integrity, dry time alone creates but a subjective preference, rather than a definition of technical requirement.
Absorbency and adsorbency
Aside from temperature, humidity and airflow, the absorbency and adsorbency of the fiber is a factor of how much water there is to evaporate. There is just one letter difference between these two words, but they have different meanings. Absorbency is the amount of water taken inside of the fiber; adsorbency is the amount of water added to its surface. The IICRC has noted that absorbency affects the drying time. Namely, natural fibers take longer to dry than synthetics because natural fibers absorb more water.
Absorbency and adsorbency numbers are given in percentages based upon their weight. Frequently, absorbency numbers are distorted because they include adsorbency, too. For an example, cotton has been reported to have absorbencies ranging from 262 percent to as high as 2,700 percent; 27 times its weight is a combination of both absorbency and adsorbency.
Another example is found in polyester. Absorbency of polyester has been given a range of 0.4 to 0.8 percent, but polyester microfiber has been reported as having adsorbency ranging from 600 to 800 percent. The lower absorbency of polyester is due to the fact it absorbs higher levels of oil; the higher adsorbency of water is due to its denier, which is the thickness of the fiber. The smaller the fiber is, the more surface area there is for water to cling to.
Imitation suedes are frequently made of polyester microfiber. They can dry as fast as other synthetics, but they adsorb water, imitating the behavior of a natural fiber. Lack of water absorbency of certain synthetic fibers, leading to a potential hyper-rapid apparent resoiling, called “wicking,” will often prescribe far shorter dry times and lesser moisture management techniques to achieve satisfaction, so no specific time interval is entirely relevant.
While longer drying times are more commonly associated with fibers with the higher water absorbency, overwetting has been more common to the fibers with the least. Overwetting on synthetic tufted carpets frequently leads to wicking; on tufted carpets with jute backings, it leads to cellulosic browning; on woven carpets with cellulosic backings, it leads to shrinkage.
In the real world of cleaning, no one will be able to adequately measure the amount of water absorbed or adsorbed to know if they are really performing low moisture.
The proper technique in managing water to achieve an aim or reduce the potential for a problem is one which takes into consideration applicable factors and implements relevant proven actions. In this regard, the technician may modify a method to manage moisture or make use of a method that inherently controls the moisture without altering its standard practices. In this way, the emphasis is on performance of an action or result, rather than a limitation that corresponds to only one criterion such as time.
The proper definition of low moisture cannot be as simple as saying it is a method, an arbitrary drying time or even based upon absorbency. One must take careful consideration of the primary aim of implementation of “low moisture” cleaning. That is, to safely clean that which may be harmed by the use of excess moisture.
The only workable definition is this one: A system in which the cleaning technician uses techniques by which there is a purposefully controlled moderation of moisture, in order to minimize drying time, prevent wicking and keep from damaging carpet or its fiber. Only then will you have what the industry seeks to define as “low moisture cleaning.”
Shawn Forsythe, a 30-plus year cleaning industry veteran, has worked in both the manufacturing and distribution fields. He uses his extensive experience as an active participant in technical IICRC groups and is a voting consensus member of the IICRC S100 cleaning standard. He can be reached at (714)423-2480.
James (Jim) B. Smith is an IICRC-approved instructor and a senior practicing inspector, as well as part of the voting consensus of the IICRC S100 cleaning standard. His educational studies come from Texas A&M University and the University of Houston. He has been in the cleaning industry since 1975. For more information, visit his website at www.CarpetInspector.com/jbs or call (972)334-0533 or (800)675-4003.