Determining Which Detergent to Use

Determining Which Detergent to Use

By Diane M. Calabrese / Published September 2017


Cleansing, or wiping clean, goes to the Latin root of the word detergent. Therefore, the goal of using a detergent is never in doubt. What about the choice of a detergent? Manufacturers of everything from asphalt to vinyl now recommend how to clean the materials and products they make. That has not always been the case.

How does a contractor choose a detergent without specific instructions in hand? Carefully. The overarching approach of contractors for decades has been twofold: Do the most with the least. And do no harm.

Thus, although treading lightly on the environment has long been part of methodology, the environment is now central. Words such as green and biodegradable enter discussions routinely. A significant point is that even a synthetic washing agent that’s designed to remove dirt and oil may be biodegradable. Prior to degrading or being assimilated by the environment in a natural way, however, some chemicals can produce unintended consequences. Recall the accelerated growth of algae (blooms) responding to abundant nutrients (e.g., nitrates, phosphorous) from terrestrial fertilizer runoff.

“Virtually all compounds in detergents are biodegradable,” says Dean Fernholz, general manager at Hydrus Detergents in Graettinger, IA. He emphasizes that definitions are important, and he welcomes absolute clarity in definitions in all federal regulations.

Fernholz’s expertise includes being licensed by the state of Iowa to operate a city water department. The licensure enables him to work with water suppliers. In one instance in a former job as a troubleshooter for a company, he located the source of the problem with a customer’s automatic parts wash as the city water supply. Chemicals were being adjusted incorrectly by the water supplier to the degree the pH had been pushed to near 10. That alkalinity neutralized the mildly acid iron phosphatizer in the parts washer, which was putting an iron phosphate coating on steel parts.

In short, things happen to the municipal water supply that are not the result of contractors using detergents. The detergent topic is a huge one, which we whittle to the essentials here.


Five questions can get a contractor on the path to a correct detergent, says Fernholz.

  • Is it a light, medium, or heavy-duty cleaning application?
  • What degree of clean does your customer require?
  • What price is your customer willing to pay?
  • Which detergent worked well in similar applications?
  • Should the detergent be applied upstream, downstream, or pre-sprayed?

A contractor can only make the best choice by knowing “the water, the cleaning application, the equipment, the detergent, and the concentration,” says Fernholz. Knowing the water means taking time to request a free water analysis from the municipal supply that will be used or using a test kit, test strips, or meters.

To successfully match a detergent to water, a contractor should know “the water hardness, pH, bicarbonates, iron content, and total dissolved solids,” says Fernholz.

Once a match is made, verify consistency. “Use a flow meter. Check pH at the nozzle.”

For many cleaning projects, one detergent will not be sufficient. Different components require different approaches, whether they are parts of a car or parts of a commercial building. Prepare in advance.

More About Choices—Q&A With Linda Chambers

We put questions to Linda Chambers, the brand and sales manager at GCE/Soap Warehouse Brand in Norcross, GA. She kindly responds.

Cleaner Times (CT): What are the top criteria for determining which detergent to use?

Chambers: First, you need to know what the dirt or stain is—its makeup; and second, what pH of detergent will be needed to break it down to remove it.

For the most part, normal dirt and stains are acidic in nature. Therefore, an alkaline product will allow for the acid, water, fats, and salts to create the process of saponification. The detergent emulsifies the dirt so that it can be washed or rinsed off of the surface that is being cleaned. The lower the pH of the dirt or stain, the higher the pH of the cleaner needs to be. You need to have at least an equal opposite of pH to work well, but having a larger difference toward the alkaline side means it will clean better and faster. Trying to use a neutral or near-neutral detergent will give you little or slow results, requiring more physical labor to be used during cleaning in order to remove the dirt or stain.

You can only learn the pH of something that is dissolved in water because pH is the measurement of hydrogen found in a liquid. So how could you know if a dry stain is acid or basic? You can know by experience, by trial and error, or by adding water to a stain and then using a pH strip to test it.

Oil and greases are usually slightly acidic, as mentioned before, and by adding salts and water we know fats or oils turn into soap with an alkaline detergent, so that one is easy.

But a natural stain, like from leaves, moss, and wood bark, is created by the tannin in them, a natural dye. To remove color dye, just like from fabric in clothes, you can use a color remover like bleach, hydrogen peroxide, or percarbonate. Acids can also sometimes work—a natural acid, vinegar, has been used for centuries to set dye into fabric and other surfaces. An acid is actually breaking down a small amount of the surface and allowing the stain to be removed with it instead of removing just the color.

If the stain or material to be removed is a mineral or metal, like iron rust, calcium efflorescence, or oxidation from aluminum, then an acid with a low pH will be needed…

CT: Are biodegradable detergents available for most cleaning jobs?

Chambers: I would say yes without question, but the real issue is with the word biodegradable itself. Biodegradable means that the substance is capable of being decomposed naturally, by bacteria or organisms, over time in a way that is not harmful. Almost everything is biodegradable given enough time. So, what are we really asking when we are asked if our cleaners are biodegradable? Are they safe, for what or whom? What may be safe to allow to be absorbed by the ground may not be the same as safe to discharge into a septic sewer.

It is not the cleaner but the substance being cleaned that really should be the issue. The same detergent used to clean out a horse trailer versus cleaning out a toxic waste tank will not be the same when it comes to being biodegradable!

Most soap detergents by themselves are biodegradable because of the natural ingredients they are made from. But some contain ingredients that can be harmful or toxic to some things, as they may be toxic to aquatic life even if perfectly natural and degradable. Detergents made with synthetic or man-made ingredients are less likely to be biodegradable.

Read the SDS [safety data sheet] to know what is in the detergent. Know what you are cleaning before you can say for sure if the waste and wastewater from the job will be biodegradable or what steps you will need to take to make them that way.

CT: Can you give an example of a difficult cleaning project?

Chambers: The most vexing cleaning issue we are asked about is how to remove oil or grease from concrete or asphalt. This used to be an easier question, although never with a perfect solution. Motor oils used to be all made from petroleum, a natural material that could be removed by using a sodium or potassium hydroxide detergent. Although, a light shadowing seemed to always be an issue no matter what was used due to the porous nature of concrete and the molecular bonding between the oil and the materials in the concrete. Sometimes the shadow could be lessened or removed by bleaching or with a mild acid.

Today vehicles oils are not just made from petroleum…but from man-made synthetic materials that are not easily broken down. They sometimes require totally new synthetic detergents as well or solvents to remove them. We now suggest that you first try hydroxides, followed by one of the butyl degreasers and finally a solvent, until the right product or combination for that particular oil is found. Newer bioengineered oil enzyme eaters have been successful for some, but not all, stubborn oil stains…

Grease stains mainly found around restaurants are slightly easier, as they are created by natural animal and vegetable oils, and hydroxides will almost always work.

The big issue when cleaning oil off asphalt is that since asphalt is itself a petroleum product, what will take out the oil stain will also remove the oils in the asphalt, and you will have color change to the area that you clean. The newer the asphalt, the more dramatic it will be. If you are not careful, you can soften and remove complete layers of asphalt from the cleaning area, while that may leave a dip or indention in the asphalt surface.