A Little About the pH Scale, for Cleaners Who Didn't Take Chemistry

Every cleaning chemical you use, in fact have ever used, has a number that places it on a scale somewhere between extremely acid and extremely base (or basic). That measurement is known as the pH scale, first used in 1909.

Both ends of the scale, which runs from 0 to 14, are extremely corrosive to human, plant and animal tissue, and also to metals. On the high, or base end (8-14) of the scale, this tendency to eat into tissue and metals is known as being caustic.



The pH level of a chemical is a measure of how easily the chemical accepts or donates a proton.

Measurement of pH regards liquids, or "aqueous solutions." References are also common to the pH of non-liquids like soil. To test soil pH, a common method is to add water and test with a pH meter. So, essentially, the soil becomes a liquid (muddy water) in order to be tested.

You may also be familiar with pH test strips which after contacting a liquid turn colors that indicate pH level. People who maintain a home pool frequently test pH, because it both affects the comfort of pool users and how other chemicals being applied are able to adjust water conditions. In other words, if the pH is outside a certain range, then other chemical adjustments don't work quite as anticipated.

"If you want a working knowledge of chemistry, don't go to school. Put in a swimming pool."

- unknown

In the middle of the pH scale is the number 7, which is the pH of water. Water is "neutral" on the scale, not acidic, nor base. Numbers lower than 7 are more base than water. Those higher than 7 are more acid.

The term base is sometimes replaced with alkaline. Alkaline, however, refers to a solution, which is always a base in pH measurement. But not all bases are alkaline, because not all bases are solutions. Soil (which is not a liquid) with a pH of 8.2, for example, is not properly referred to as being alkaline, but rather as base. 

Fun Fact: The optimal soil pH for most plants runs between 5.5 (acid) and 7.0 (neutral). Plants like it on the acidic side of things - cropnutrition.com

The terms salty and alkaline are sometimes used for one another. All salts are alkaline (base), however, not all alkalines are salts. In other words, they are not the same thing, and the terms are not interchangeable on the pH scale.

So, to keep life simple, stick with acid for numbers lower than seven and base for numbers higher than seven on the scale, and you should be in good shape if your high school chemistry professor stops by for a beer.

The pH of a New Belgium Twisted Spoke
is 3.14.

- embracethefunk.com, a beer aficionado site

Why is water smack dab in the middle of the
pH chart?

Note that we are talking about "pure" water being in the center. Pure water is something most of us seldom, or never, come in contact with. Tap and even bottled water often have additional elements (impurities, chlorine, minerals, etc.) that affect the water's actual pH.

Here's what your chemistry teacher might have said: 

A water molecule consists of a hydrogen ion bonded to a hydroxide ion. The hydrogen ion is positively charged, while the hydroxide has a negative charge. This gives water an overall electric charge of zero. - reference.com

Basically, if ions and hydroxides are not in your daily lexicon, pure water has an essentially balanced amount of positive and negative charges, so it is "neutral." It has no charge and is neither acid nor base.

SO, What does "pH" STAND FOR, and where did it come from?

The term "pH" was first described by Danish biochemist Søren Peter Lauritz Sørensen in 1909. pH is an abbreviation for "power of hydrogen" where "p" is short for the German word for power, "potenz," and H is the element symbol for hydrogen. The H is capitalized because it is standard to capitalize element symbols. - about.chemistry.com

BOTTOM LINE, Why is pH important IN cleaning?

Acids clean faster than bases (alkalines).

Right off the bat, if you have a cleaner with a pH of 12 (base) and a cleaner with a pH of 2 (acid), the more acidic cleaner will do its job faster. Both cleaners would be five away from neutral (7) on the scale, but base/alkaline cleaners take more time to work.

Take special care with low and high pH products.

From a personal protective equipment standpoint, if a product has a fairly low number or one toward the higher end of the scale, both situations are going to be increasingly dangerous to people and harmful to surfaces. (Obviously, it is thought to be "just right" for that product's label-specific purposes.) Because the scale is logarithmic, there is a factor of ten between each number. In the infographic of the pH scale above, we have made this a little easier to visualize by using money - starting with a penny at "neutral" and spreading in both directions, acid and base.

When cleaning chemicals are blended, they are created by mixing other chemicals that have varying pH values. Once blended, there will be a resulting overall pH for that product. Every product can be measured for its exact pH. Two different products can have the same pH just like two different days can have the same temperature.

Unexpected pH provides a warning. 

The pH of products is often tested during or after production. Changed pH may warn you of a product imperfection. If the pH is different from the norm, the product may have been mixed in the wrong proportions, or a wrong ingredient might have been used. If the product was sitting in a janitorial closet and has a different pH than it should, perhaps the product has expired and chemical reactions have taken place that changed the pH. This is one reason some cleaning chemistry has expiration dates posted on the label. After that time, stability of the atoms making up the product inside is not guaranteed. If the product does change over time, then it is not the original chemical, and the results from using it may be significantly different from the ones you wanted. This suggests you should always check label expiration dates and adhere to them.

Cleaning processes often require the right pH to work.

When using cleaning chemistry, particularly in processes where one chemical follows another, it is important to achieve certain pH levels at certain points in the process for the next step to work properly. In floor finishing, for example, after stripping - a very base pH process - it is necessary to bring the floor down to a lower or neutral pH (6.8 to 7.2 is considered neutral in most cases) for the finish application stage to begin.

Because strippers have traditionally had a very high pH*, they are one in a group of products requiring great care and precaution. New, greener strippers are certified by Green Seal at no higher than 11.5 pH**. It is almost certainly worthwhile for your department to consider new stripper formulations that may fit your needs better than the technologies of the past. 

The closer to pH 7, the less harsh a cleaner is.

In general cleaning, more-neutral cleaners are easier on surfaces. Higher or lower pH levels are one factor that affects chemistry "harshness," a non-technical term that refers to how punishing a product can be on surfaces (or exposed skin) after repeated use. Because most soils are acidic in nature, many cleaners are slightly base in composition by design. The resulting neutralizing process allows soils to become easier to remove.


PH is simply one in a range of product attributes that can tell you more about any cleaning chemistry and its characteristics. When using products in step-by-step processes, it is often critically important to read label instructions to know the required pH of the next product so that the desired result can be obtained. Neutralizing floors before refinishing has always been a critical step in getting the best finish and adhesion.

And finally, the pH of a product can tell you something about dangers it may hold for you, or for surfaces. When using chemistry of very high or low pH, wear recommended PPE, personal protective equipment, and focus on the job at hand.

Ask your PUR-O-ZONE representative for a copy of the pH Scale sign above, or fill out the contact form on this website to request one. 

*Many strippers also have a high VOC content, and permeate areas being stripped with fumes that are unwanted, but have traditionally just been a necessary part of the process. Ask your PUR-O-ZONE representative about more-green formulations for improving safety and sustainability in your department.

**There are, of course, other measurements that Green Seal also judges floor stripper chemistry on before it is certified as green, but pH is certainly an important one.