The CRI SOA spectrophotometre (DE) analysis of soil removal demonstrates that in-tank application of cleaning detergent during hot water extraction cleaning produces comparative soil removal using average DE values 4.6% over flushing with plain hot water. When a pre- conditioner is applied to a carpet before attempting soil removal using industry-accepted hot water extraction cleaning techniques, analysis of comparative soil removal using DE values increased to an average of 16.3% over hot water flushing alone.
Overall, cleaning with chemicals used exclusively in the solution tanks of hot water extraction units achieved soil removal only slightly better than flushing with plain water; whereas, chemicals pre-applied in the preconditioning process, followed by hot water rinsing, cleaned significantly better than chemicals applied through in-tank solutions in the course of hot water extraction.
To understand the relationship between the preconditioning process in overall cleaning, it is prudent to discuss this process within the context of hot water extraction cleaning principles. The IICRC S100 Standard and Reference Guide for Professional Carpet Cleaning sets forth five “principles” of cleaning, at least four of which apply to all carpet cleaning efforts, if soil suspension and removal are to be maximised. They are:
- dry soil removal
- soil suspension
- suspended soil removal
- grooming, as necessary
The principles of cleaning incorporate the use of two media for soil removal – air and liquids. Chemicals – properly formulated, mixed and applied when using liquid media – enhance soil suspension, and ultimately, the suspended soil’s physical removal from carpet.
Dry Soil Removal
This is the first principle of cleaning, according to the IICRC S100. As per the industry surveys conducted by DuPont and others, some 74-79% of carpet soil is particulate or protein and cellulosic fibre. These soils not only have the potential to be removed with dry vacuuming but if not so removed, when wetted during chemical application or in the course of being flushed from pile yarns, they increase in weight and become more difficult to be removed.
Once dry particle soil has been removed from a carpet to the extent practical, cleaners should begin soil suspension (preconditioning) procedures. Soil suspension or separation of fine particle, water-soluble and oily soils from fibre surfaces, is a critical step in state-of-the-art, professional cleaning.
The goal of soil suspension is to separate soil from fibre surfaces and hold it in suspension until physical removal can take place. This goal should be achieved using properly formulated, mixed and applied cleaning chemicals (detergents). Preconditioning or applying proper chemicals before attempting physical soil removal, is an essential step in achieving that goal.
There are four fundamental activities to be accomplished under the soil suspension principle. These are known as the ‘‘fundamentals of soil suspension.” They include chemical action, heat or temperature, agitation and time. The industry-coined acronym, for these is “CHAT”.
Chemicals are used to prepare carpet for cleaning by reducing the surface tension of water and by suspending, sequestering, emulsifying and saponifying the various types of soil. This procedure is referred to as “preconditioning the carpet” – an essential step for thorough cleaning. The second phase of chemical activity occurs when chemicals are mixed or metred into rinse solutions to suspend light (usually atmospheric) soils that settle on and accumulate in non-trafficked areas along baseboards or under furniture. Chemicals applied during preconditioning are essential for quality, state-of-the-art cleaning.
Heat temperature fundamental that relates to soil suspension simply acknowledges the fact that heat reduces the surface tension of water, enabling it to clean faster and more efficiently than cold water. It is merely a matter of thermodynamics or the ability of heat to accelerate the activity of the chemicals employed in the course of cleaning.
Time is the last fundamental under the soil suspension principle and it probably is the least considered. Residential carpet that is cleaned with any regularity (over and above routine vacuuming) may be cleaned on an average of once every 12 to 24 months. No other textile fabric receives as much heavy, ground-in soil with so little regular cleaning. Of the soils that are deposited over this period, none are more difficult to suspend and remove than oils that have dried out or “oxidized.”
Suspended Soil Removal Principle
By definition, soil is unwanted substance foreign to the construction of carpet. At this point, in employing cleaning principles, soils that could not be removed using dry vacuuming have been dissolved, emulsified, separated or suspended from fibre surfaces. In addition, the soil that was evenly spread out causing the carpet to look grey and dingy, has now been reduced to fewer, larger (though still less visible) masses of particles, and the carpet also looks relatively “clean”. However, to achieve state-of-the-art cleaning, this soil still must be removed physically (extracted or rinsed) as completely as possible from the carpet’s pile.
Finishing (Grooming) Principle
The term “finishing” refers to any procedure used to enhance the appearance of the carpet beyond the physical soil removal process. Generally, pile setting or grooming, using appropriate brushes or combs, should be performed in this context, especially on residential carpet styles with higher pile height. Grooming carpet is important to leave the carpet in its most pleasing appearance for customer viewing. Grooming untangles yarns, eliminates cleaning tool patterns and breaks up distortion that might be interpreted as matting, crushing or wear and generate complaints for carpet manufacturers.
A cleaning project is not complete until provisions are made to return carpet to its intended use. Effort to dry carpet as expeditiously as practical, should be made for several reasons: First, it is required to return the carpet to use by customers as soon as practical. Second, drying carpet essentially eliminates slip-fall hazards, especially in areas where carpet transitions to wood, laminate, linoleum, VCT, sheet vinyl, tile or stone flooring. Third, rapid drying eliminates musty odours that may be associated with prolonged dampness. Moreover, it eliminates the potential for microbial germination, growth, amplification and dissemination, along with real or perceived EQ or health concerns that may arise if carpet stays damp too long.