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Carpet Cleaning Residue

No matter which method of carpet cleaning you use, you are going to leave behind residues. You can pre-condition with any type of detergent, use an alkaline rinse, an acid rinse, or water rinse, and you are going to leave behind residues. That seems bad, but it doesn't have to be.

Types of Residues

If you were in the carpet cleaning industry 20 years ago, you probably remember the popularity of alkaline pre-conditioners, alkaline rinses, and the heavy use of acid chemical oversprays to try to fix carpet problems that often resulted.

Cleaners were frustrated with white or light-colored carpets that tended to "yellow" but were fixed with an acid overspray. Those return trips to fix a problem didn't pay very well. They were also frustrated with complaints by customers saying that the carpet cleaned recently was dirty again.


Those Days Are Long Gone

Today, you can still clean with alkaline-based rinses (formulations are much better now), but most cleaners find success by using an acid rinse, which strips away soils and preconditioning detergents and leaves the carpet fiber soft to the touch and less likely to become the victim of the dreaded "rapid resoiling" foe.

(Note: Furniture fibers also benefit from this information. They too need the proper type of residue left behind.)

Basically, the type of residues most common include:

  • Alkaline rinse/residue
  • Acid rinse/residue
  • Neutral rinse/residue
  • Water rinse/residue
  • Compound residue

Solving a Problem

One problem many cleaners come across is heavy detergent load in a carpet, and when cleaning begins, huge amounts of foam slows down the cleaning process. To solve this problem, turn off your heat. Use a cold water rinse (or cold water acid rinse) and the detergent will not foam nearly as much.

You can also add defoamer to your waste tank (most common) or to the carpet itself (some powdered defoamers are made for this).

Which Type of Residue is Best?

Alkaline rinses/residues are good shoe cleaners. Think about it: What does alkalinity do to soils? It strips soils from other surfaces.

  • A strong alkaline residue (There are good mild alkaline rinses on the market, but we are talking about higher pH in this technical bulletin) will leave a carpet "crusty" to the touch and will re-soil rapidly as it attracts soils to the fibers.
  • Acid rinses/residues neutralize your alkaline pre-conditioner (if that is what you are using) and leave the carpet with a soft "hand" or feel, and do not attract soils if used properly. Remember, always follow manufacturer directions. Doubling up on chemical isn't smart.
  • Neutral rinses/residues are gaining popularity as they still have good surfactancy yet are neutral on the pH scale. Water does not qualify as a neutral rinse in the context of this technical bulletin.
  • Water rinses/residues are also popular (and free!) but the problem with using water as your rinse alone is you have no chemical action to balance the pre-conditioner in the carpet, along with no chemistry to continue the cleaning process (except for the cleaning power of water alone).
Of course, the hotter, the better... but if you are applying chemicals to the carpet and using a water-only rinse, you need to ensure you are removing as much of the chemical as possible.

Compound residue is the result of using either a synthetic or natural compound cleaner in the absorbent compound category. The goal of compound cleaning is to use very low moisture and remove as much soil as possible without leaving behind sticky detergents. Subsequent vacuuming removes more of the compound residue and also more of the soil in the carpet (also the goal of encapsulation chemistry). A huge benefit of compound cleaning is that the carpet can be used almost immediately after it is cleaned.

Test for Yourself

There are ways you can determine for yourself which type of residue is best. A simple test is to clean areas of a carpet in your own home or business, using various type of rinses (or no rinse at all), and gauge how fast each area re-soils.

Another way to test is to put small amounts of the rinsing agent on a glass plate (rinses mixed according to directions) and allow to dry. Then, using your finger, see which ones flake off or are powdery, and which ones seem sticky. You want to use the type that flakes or is powdery; anything sticky is a mistake.

Most encapsulation rinses are on the acid side of the pH scale, and they are good choices for many cleaning applications.

Using the pH Test

An easy way to see if your rinsing agent is doing its job in balancing alkaline pre-conditioners, is to test the carpet pH after you have cleaned it.Testing the pH of your cleaning solutions is a good guide, but it's not the final result. You must test the fiber.After cleaning, put a small amount of litmus paper (pH paper) on the carpet. If you are not getting the desired pH reading you wish (most are looking for an acid reading) then you need to determine if the cleaning chemistry you are using is best.

Many professional cleaners have their own opinion on which type of rinse is best; now it's your turn to form your own opinion.

The most important goal? Use what works best for your company or your facility.