Cleaning Tips: The Value of Measuring pH

Practical advice to get the job done more efficiently

Professional carpet cleaners know that effective cleaning depends on measuring the pH of the soil or stain. Quick and easy ways to test the pH of a stain include using litmus paper, pH paper or an electronic pH meter. You can also use the same items to test the pH of your cleaning solution. Cleaning solutions and carpet stains fall into one of three pH categories:

acidic (with a pH reading of less than 7), neutral (pH of 7) or alkaline (pH over 7). If you know the pH of the spot, you should use a cleaner with an opposite pH to remove the soil. As a rule of thumb, all-purpose carpet cleaners are usually alkaline (high pH) cleaners, since most stains fall into the acid category.

Adhering to these general guidelines will help you clean carpet effectively. But there’s a lot more to pH than the basics, and if you want to take your business to the next level, it pays to develop a more in-depth understanding of pH. According to James Smith in a recent article at, “We must remember that nylon and wool are the two fibers most likely to need definitive alkaline limits.” Since that pertains to many of your jobs, it’s worth digging deeper into Smith’s article. His sound advice includes the following:

  • “In most cases, wool should not be over a pH of 5.5. This would include before it is cleaned, during its cleaning, and afterwards. If wool’s reading is higher than this, its polarity will revert to its natural anionic state and it will no longer have colorfastness with acid-dyes.”
  • “It is just an educated guess, but nylon should not have a pH higher than 8. It needs a pH higher than 7 for detergency to reach a satisfactory level. Higher than 8 indicates that its stain resistance is likely damaged. Soil’s pH is generally from 6.1 to 6.7.”

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