Game Plan: Soil Suspension
The purpose of the “Game Plan” is to explore in detail the technical or mechanical process of cleaning carpet. This process involves following the steps set forth in S100, the Standard and Reference Guide for Carpet Cleaning, by The Clean Trust (formerly the IICRC). Those steps are:
1. Dry Soil Removal
2. Soil Suspension
3. Soil Extraction
4. Finishing or Grooming
Previous conversations centered on the first step, dry soil removal. This month, I’ll continue the conversation about the second step, soil suspension. The argument can be made that this step may be the most important step in the entire process. Not to minimize any step, but it’s just that if we don’t get the soil loosened from the fiber, we’re likely to have poor final results. When we examine other cleaning processes, such as washing clothes, the soil suspension step is by far the most extensive, with the most obvious part of the mechanism being labeled the “agitator.” The most significant part of washing ones hands is the thorough agitation, or scrubbing action, to loosen soil. This brings us to the four fundamentals of soil suspension: “TACT.” Last month, I discussed the chemistry part of soil suspension (hence, the “C” in TACT) and the importance of using pre-sprays that maximize the potential to remove the soil from the fiber being cleaned, while taking into account the fiber and degree of soil. The other fundamentals - temperature (T), agitation (A) and time (T) - complement the action of the chemical pre-spray.
Many instructors used to illustrate the importance of heat in the soil suspension process by referring to “Arrhenius’ Law” with the statement that, “chemical activity doubles with each 18 degree increase in heat, starting at 118 degrees.” The exact interpretation of that law has been challenged, but nevertheless, adding heat to the pre-spray improves the action of the chemistry. If one applies a pre-spray with a siphon type sprayer, the heat will be very good and constant. The only consideration one should take into account when using such a sprayer is the type of chemistry in the solution line - acid, alkaline, or neutral - and the possible effect that it might have on the desired chemistry of the pre-spray.
If a pump-up sprayer or an electric sprayer is used to apply the pre-spray, one should use the hottest water available. The disadvantage of this type of application is that the water will cool over time and the advantage of heat is lost. Understanding that we have lost the advantage of heat, we would then apply a greater amount of one or both of the remaining two fundamentals of soil suspension: agitation (A) and time (T).
I’m partial to the agitation part of the soil suspension process, because in our company we utilize a 175 rpm rotary machine with a shampoo brush to facilitate the agitation process. This is the ultimate application of the agitation portion of soil suspension. With a good pre-spray or a carpet shampoo, this is tantamount to instant soil suspension. Unfortunately, very few carpet cleaners have the luxury of being able to haul a rotary shampoo machine around with them. A good option would be to utilize a rotary extraction tool during the agitation phase. The next best piece of equipment would be a counter-rotating brush machine, which is again, not widely utilized. For the vast majority of cleaners, the only tool available to use for agitation is a carpet grooming tool. Agitation with a carpet grooming tool, when done correctly, is similar to doing an upper body workout, depending on the weight of the carpet, the size of the area being cleaned and the degree of soil. I would venture to say that the biggest reason for poor soil suspension is poor agitation.
The time (T) portion of the soil suspension is perhaps the easiest to utilize. After the hot pre-spray has been correctly applied to the carpet - more in the highly soiled areas, and less in the lightly soiled areas - and adequately agitated, the last fundamental to apply is time, usually referred to as “dwell time.” Unless a cleaner has used some form of mechanical action, the pre-spray will require some time to suspend and emulsify the fluid soil. This dwell time is typically five to 15 minutes for traditional pre-sprays (but possibly longer for green-certified pre-sprays). Enzyme dominated pre-sprays can require extended dwell times depending on the extensiveness of the protein soil.
The four fundamentals of soil suspension (TACT), when properly understood and properly applied, are arguably the most critical step in successfully removing the maximum amount of soil.
I’d like to give a big shout-out to “GP.” GP works for a large cleaning company in a northern city. He has worked for the company for 33 years, which is almost unheard of in this industry. He is still the largest producer, maintains a great attitude and makes a very good living. GP is a true cleaning professional.
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