The 7 Most Common Misconceptions about Carpet Cleaning Chemistry – Part 4 – When pH is measured

Misconception #4 – Where is pH measured? Concentrated or ready-to-use pH.

Quick, think about the discussion we just had on stain resistant warranty provisions and the pH of the cleaning solution. You already knew about the 10 pH rule. But how is that pH measured? Is it the concentrated pH of the cleaning solution in the bottle before it is mixed, or is it the pH of the cleaning solution after it has been diluted and mixed? The fact is, most literature does not say. Now common sense may dictate that we are primarily concerned with the pH of the solution as it is being used on the carpet. That would be ready-to-use pH.

But think about this for a moment. Suppose you have a concentrated carpet prespray with a pH of 11. The directions call for mixing it 1:32 (four ounces of solution in a gallon of water). After you dilute it, the pH drops to 9.8 (how much the pH “moves” is going to be contingent upon the buffering of the solution and the water you are mixing it with – but that is for another discussion). So, if you are trying to clean the carpet with a solution below the 10 pH threshold, you are good to go, right? Well, no cleaning solution you apply, especially as a prespray, is going to be 100% residue free. What that means is that some of the prespray or extraction detergent you use to clean the carpet is going to be left behind in the carpet. Hopefully, if you are using a quality formulation, it is a minute amount. But it is there none-the-less. Now, what happens to the pH of that solution as the water evaporates out of it? Yup, you guessed it. It returns to its original concentrated pH. In the case we mentioned, the residue has a pH of 11, not 9.8.

That is the reason why a lot of teachers teach and formulators push using an acid rinse or neutralizing rinse solution, to make sure if you used a higher pH carpet prespray, that you neutralized that residue. That is a good practice, but using an alkaline detergent rinse has some advantages over an acid rinse too. We will leave that for misconception #6.

HydraMaster formulates its carpet presprays, extraction detergents, and neutralizing rinses to be highly buffered, meaning that they will maintain their pH as they are diluted according to directions. After all, if a solution is not buffered and you dilute it heavily, then everything would have a neutral pH.