We often read the term “acid rinse” in various carpet cleaning publications, but what does it actually mean and how is it done and why? And, should we even use the term “acid rinse”?
Strictly speaking, "acid rinse" simply means that, after extraction cleaning the carpet, an acid-based product is run through the machine to rinse out detergent residue in the carpet, rug or upholstery and to decrease the pH by neutralizing the alkaline components of the cleaning compound used.
What is the history of the term “Acid Rinse”?
Historically, when carpets were constructed with jute backing, the jute would often bleed out brown lignin resulting with a "browning" residue on the tips of the carpet fibers. Additionally, in the “old days”, high-pH detergents were often used to clean carpet, leaving a high pH residue on the surface. An acid product or browning agent had to be applied to prevent browning and chemical yellowing and also to stabilize the carpet or rug dyes.
When and how should an “acid rinse” be used?
We recommend the use of what some call an acid rinse but what we call a Brown Out rinse or Brown Out flush, which is used by adding 2 or more ounces of Brown Out® per gallon of water (no detergent) through the base unit only when we need to get the pH down, have detergent residue of ice melt track-in or a lot of detergent residue from previous cleanings. In this procedure, extraction clean with the Brown Out solution using plenty of vacuum-only strokes to leave carpet as dry as possible.
Should we use the term “acid rinse”?
We never use the word “acid rinse”in front of a customer! The term “acid”, in the minds of the customer, signals “danger - poison”! Instead, we call it a Brown Out rinse or Brown Out flush.
Does an “acid rinse” remove detergent residue?
Some preach prespraying and then using an “acid rinse” to neutralize the detergent and leave no residue. I continue to be amazed that anyone actually believes that an acid leaves no residue or that an acid will somehow magically “zap” the prespray and make it disappear into thin air! Acetic acid (vinegar) will evaporate, but the acetate salt formed when it neutralizes alkali does not evaporate. Some use hydroxyacetic acid, but its evaporation rate is slow and its salts also don’t evaporate. Additionally, acetic acid and hydroxyacetic acid, have an odor that is objectionable to most customers.
What conditions might require a “Brown Out Flush” or “Acid Rinse”?
If a non-extraction system was used for the cleaning, there may be a great deal of soil attracting residue in the carpet. Moisten an area with water and agitate with a Carpet Shark. If a significant amount of foam is generated, a detergent residue was left behind. Bonnet cleaning and the shampoo methods are infamous for this problem.
Additional Acid Rinse Related Information: