pH 101: What You Need to Know About Carpets and pH
If you’re just starting out, you probably haven’t thought much about pH since lab in high school. While it isn’t the only factor when it comes to carpet chemistry, any seasoned carpet cleaner can tell you it’s crucial to know at least the basics (pun intended). So we wrote the following as a quick guide to get you familiar with how pH affects carpet cleaning results, and some general tips to keep you out of trouble.
First, for those that need a refresher; pH is a measure of the acidity/alkalinity of a solution. The pH scale goes from 0-14, with 0 being the most acidic, 14 being the most alkaline and 7 being neutral. Each number on the scale is 10x the previous, I.e. a solution with a pH of 4 is 10x more acidic than one with a pH of 5, and 100x more acidic than pH 6. pH stands for potential Hydrogen, because what it’s actually measuring is the concentration of hydrogen/hydroxyl ions in a solution. These ions are what are responsible for the reaction we typically think of when something is exposed to acids or alkaline solutions.
So how does pH factor into your cleaning?
Well, spots, stains, and soils all have their own pH level, and knowing what they are helps determine the most effective pH to clean them with. Since most soils you will encounter in carpet cleaning are acidic, most carpet cleaning chemicals and presprays are alkaline. Now, there are also many types of carpet fiber out there, with varying degrees of tolerance for high/low pH (we’ll cover specifics below). The key is finding a balance that is effective at breaking down the soils present but isn’t damaging to the fibers of the carpet.
To get the best idea of what you’re getting into, determine what type of carpet it is (both face yarn and backing) and what pH it’s resting at before you do anything else to it! We recommend having a pH meter handy to test spots/ spills and the carpet itself! While generally, carpets rest at a pH below neutral, leftover residues from previous carpet cleaners or stain spotters used by homeowners can leave the carpet in an alkaline state. Carpets in this state generally won’t need the same level of treatment as a low pH carpet and are prime for over-applying chemicals.
Nylon, polyester, and olefin are all examples of synthetic fibers, and the most common in wall-to-wall carpeting. In general, synthetic fibers are more tolerant of high pH’s than natural fibers are, but there’s still a limit. The broad rule for synthetics is you can safely clean them all with up to a pH of 10 without causing harm. Now, of course, all rules are meant to be broken, but for cleaners still just learning the ropes, following this one will help keep you out of trouble.
Wool, silk, cotton, jute, and sisal are all examples of natural fiber. In the case of wall-to-wall carpets, wool is the most common natural fiber being used today, but overall natural fibers are much less prevalent than synthetic–at least in the U.S. (Wool carpet is much more common in countries like Australia and New Zealand). For wool cleaning, a pH ranging from 5 to 8 is generally considered in the “safe zone”, which novice cleaners would be wise to stick to. There are also products with specific wool certifications that can be trusted, even if outside the safe zone.
Other types of natural fiber are much less common for wall-to-wall applications and are becoming even rarer due to other options like synthetics being cheaper and easier to care for. You may still encounter carpets with a jute backing, however. In those cases treat similar to wool, only mild solutions should be used, and it should be returned to an acidic state to avoid issues like browning after cleaning.
What pH should you leave the carpet?
We’ve covered how to use pH to your advantage while cleaning, but what about after the carpet is cleaned? Believe it or not, the pH you leave the carpets with is arguably just as important as what you cleaned them at. Alkaline residue in carpets will attract dirt and cause rapid re-soiling. Depending on the type of fiber, it may also have other undesirable effects like stiff, crunchy carpets – even color loss and browning may occur! To avoid these nightmares, your goal should be to leave the carpet or textile as close to its natural pH as possible, which is almost always neutral to slightly acidic. This is why products like acid rinses are so popular; low pH rinses will help to neutralize alkalinity from your prespray, and remove more residue than water alone.
Let’s sum up what we’ve learned:
- pH is a measure of the potential of hydrogen in a solution. It has a scale from 0-14 with 7 being neutral, 0 being the most acidic, and 14 being the most basic.
- Most dirt and soils found in carpets are mildly acidic.
- Most cleaning chemicals and carpet presprays are alkaline.
- You should have a pH meter somewhere on hand.
- pH doesn’t paint the whole picture when it comes to cleaning chemistry, but it’s still very important to understand the basics.
- Synthetic fibers are the most prevalent nowadays and can be safely cleaned with a pH of up to 10.
- Natural fibers are becoming less common but are still likely to be encountered at some point. They are more sensitive to high pH than synthetic fibers, and you are best off taking a milder approach.
- It’s important when using strong alkaline cleaners to return the carpet to a neutral to slightly acidic level. This is most commonly achieved with an acid rinse.