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Using the word “chemistry” is risky business. People have such a visceral reaction to the word. But chemicals are around us everyday, and we use different chemicals for various jobs all the time. For example:
- You used soap when you showered today (at least I hope you did!), which is a chemical designed to remove dirt.
- And you sprayed that air freshener after the dog got soaked in the rain and slept next to your bed. Another chemical, designed to smell good and destroy foul odors.
We use chemistry everyday, and take it for granted. Just think about a world without gasoline, a combustible mix of chemicals that runs millions of engines, large and small!
But when we get to the subject of stain removal, we hope one stain cleaner will remove every substance that might soil our car’s interior. And why not expect a lot, we live in an age of miracles where you can order a pizza by touching a button on your phone. So the real question is:
Do you really need all those different stain removers you see on the store’s shelf?
Yes! You need to use a spot remover designed to work on your specific stain.
So, with a quick nerd warning (it feels like a warning is needed these days after always seeing spoiler warnings), let’s explore the reasons why one product cannot possibly remove every stain out there.
So What Is pH Anyway?
Let’s start with something simple: Water
Most of us know water is H2O, or another way to write it is H-O-H. This can be broken into two parts: H+ (hydrogen ions) and OH– (hydroxyl ions). This is important because if a solution has an excess of H+, you have an acid solution. And if you have an excess of OH–, you have an alkaline solution (or a base).
So, the pH scale is a way of determining whether your solution is an acid or an alkali. Yes I have simplified a little here, but it is important to mention this for a couple of reasons.
The first is that pH is a property of aqueous solutions (that’s how the chemists like to say it, but it just means water based!). So, in order to have a pH, the solution must be water based. And when you state you have an acid or an alkali solution, you are identifying whether there is an excess of positively charged hydrogen ions or negatively charged hydroxyl ions.
That brings us to the second important point. The positive hydrogen ions are missing electrons, and the negative hydroxyl ions have excess electrons. Don’t worry, it is not important to understand how this all works, just that they are very different things, opposites in fact. With this knowledge, you can see it is not surprising to find out that they react very different with other chemicals (like say for instance, stains).
Bonus: You may now also understand why when you were a kid and mixed vinegar with baking soda, it fizzed so readily. Vinegar is an acid, and when you dissolve baking soda in the vinegar’s water, you get an alkali solution. The alkaline baking soda gives up its electrons to the acidic vinegar and … fake volcano!
Now back to the pH scale. The scale runs from 0 to 14, with 0 being very acidic, 14 being very alkaline, and 7 being neutral. And an important thing to understand about this scale, it’s logarithmic. Yeah, I know, another fancy word, but it is important to us because each number on the scale means the concentrations jump ten times. For example:
- 3 is ten times more acidic than 4,
- 9 is ten times more alkaline than 8,
- 2 is one hundred times more acidic than 4,
- 10 is one hundred times more alkaline than 8,
- and so on.
So, yes, the pH subject is complex and you may have asked a few times if you read this far:
Why is pH important in explaining how stain removers work?
Good question and that leads us to the next subject, ways to “design” a spot remover.
How to Design a Cleaner
And I am sure you noticed, the first two choices employ a knowledge of pH to help remove a stain. Now it may make that painful technical pH dissertation more understandable.
So, imagine you just landed your first job in with a well known cleaning product company, working in the lab. You are asked to develop a formula to clean ____ (you fill in the blank, it could be motor oil, ketchup, lipstick, or even vomit). So you wonder:
How do you go about designing a stain cleaner?
Well, in general you have a few options, and these are:
- Adjust the pH to modify the solubility of the stain.
- Use pH to react with and break down the stain in water-soluble by-products (in this case you use an acid on an alkali substance, or and alkai on an acid substance).
- Add wetting agents (typically silicone compounds) to the cleaner and make the stain “accept” water better.
- Use surfactants (soaps) to provide a “bridge” between the stain and water molecules so that it dissolves.
- Employ enzymes to break down the stain into water-soluble components.
- Special mention: Heat (use with caution!)
Let’s discuss each option in a little detail.
1. Adjust pH to Make the Stain More Soluble in Water
Pure water is neutral, with a pH of 7. It will not dissolve substances like hair gel or tomato sauce very well on its own, but if you shift the pH to the acid side of the scale, it dissolves these substances more readily. The same is true with many alkali things, like say makeup, except these like to dissolve more readily in an alkaline solution.
So we can use pH to make the stain easier to dissolve into water, meaning it is lifted by water and washed away more easily. The rule of thumb here is to employ a cleaning solution with a pH similar to the stain. But this technique will not always completely remove the stain, and other “tricks” may need to be employed by the formulator.
The number of acidic and alkaline solutions (also called acids and bases) available to use in a cleaning product are large, but the formulator has to take some care. Some will stain fabric (not great for an upholstery cleaner when the product itself stains), and some will damage things like leather and vinyl. Plus some will induce rashes or leave foul odors. So, there is much to consider when selecting an acid or base to use in a stain remover.
2. Use pH to Break Down the Stain
The second way to use the pH of a water based cleaner is to wreak havoc, break things. Yes, we can break down the stain into simpler, easier to dissolve pieces (or molecules as the nerdy types like to say). If the stain remover employs this strategy, the pH of the cleaner is typically the “opposite” of the stain pH (e.g. an acid based cleaner is used on an alkaline stain, or vice versa).
There are thousands of acid and alkaline solutions a formulator can employ. But to get the best cleaning action, a specific acid or base has to selected to clean a given stain. And because stains vary in their chemistry (that french fry oil is not the same as that grass stain), it is impossible to find a solution, based on pH alone, that cleans everything. So a cleaning product is often designed to clean specific types of stains.
And again, care must again be taken when using an acid or base as a way of breaking down a stain. Many acids will break down your stain, but they will also break down your fabric and leather. It is stating the obvious, but the goal is to break down the stain without harming the car’s interior.
Plus, don’t forget that many of the strong acids and bases are harmful to people. So adding them to a cleaning product intended for an enclosed space (a car’s interior) is not practicable.
3. Add Wetting Agents
There are a group of chemicals that can be added to water to make it “wetter.” That sounds counter intuitive, but we all know water possesses significant surface tension. You say you didn’t know that? But you do. Anyone who has done a belly flop can attest to it with their bright red stomach.
This high surface tension is a problem when trying to get certain things to dissolve in water. Water and many stains do not always interact well. But a wetting agent can help the water interface with the foreign substance, making it easier to dissolve, and therefore clean the stain.
Many of the wetting agents that can be added to a spot remover are in the silicone family, and those chemicals are not always considered desirable in an automotive detailing shop. So read the label carefully, some cleaners do have silicones in them.
4. Use Surfactants to Provide a “Bridge”
Surfactants in the form of detergents and soap is one chemical we use everyday. The concept is simple. Try and dissolve ordinary dirt in pure water. You will see it is impossible.
This has to do with the polarity (or lack of polarity) of the water and dirt molecules and the explanation can get pretty deep into the chemistry of these molecules. But to keep it simple, let’s just say there is no place for the water to grip onto the dirt. This is where surface active agents (a.k.a. surfactants) come into play. One end of the surfactant molecule has a good way to grip onto the dirt molecules. And the other end of the surfactant molecule has a way to grip onto water molecules. This creates a “bridge” between the water and dirt, and now the dirt can be dissolved in the soapy water and washed away.
There are thousands of surfactants, and the selection of a specific surfactant will impact which kinds of stains will be lifted. So once again, a formulator is forced to focus on the type of stain to be removed.
5. Employ enzymes
One way to remove stains is to go all Hulk and bust them up into itty-bitty, tiny little pieces! (Hey, why can’t an Avenger fight a stain?) Sorry, the image of tiny little Hulks smashing a stain on a molecular level was too funny not to share, but let’s get back to the real world and the serious science of cleaning stains.
We mentioned how some cleaners break down stains by use of an acid or an alkali solution, but that is not possible with with many stains. However, there is another way to break stains down into smaller, water soluble pieces.
Enzymes are chemicals that specialize in taking large molecules and reducing them to smaller parts. This is quite useful when designing a stain cleaner. The smaller pieces are easy for water to dissolve, and hence, easier to clean.
So what are enzymes? This group of chemicals is misunderstood, and many believe that they are bacteria. But this is false. I think some of the confusion happens because bacteria do use enzymes to function. And you can use enzymes together with bacteria to make the micro-organisms more effective (you will some products labeled as bio-enzymatic cleaners, meaning they have both an enzyme and bacteria). However, be assured enzymes are a chemical family, and that they are not alive.
And like most families at Thanksgiving, there are many, many members of the enzyme family you can seat at the adult table. In other words, when formulating a cleaner, you need to select an enzyme that is effective at breaking down the specific type of stain (i.e. a specific chemistry). Because the source of the stains in our cars varies (e.g. mustard to dirt to oil to makeup), the formulator must make various cleaners with different enzymes to make the most effective cleaners.
We need to make on special mention: the use of heat.
On some stains, it is important to NOT use heat. These are typically the protein based stains (e.g. blood, excrement, egg, vomit, etc.). Heat causes substances like this to coagulate, and they become a mess that is almost impossible to clean. Spot cleaners designed to clean these types of stains will typically caution against using hot water for this reason.
But you will see times when a cleaning product says “use warm water.” This is another trick of the trade, and most of us know many chemicals dissolve better in warm water. Think of sugar dissolving in hot coffee versus sugar dissolving in ice tea. Yeah, heat helps!
So read the label. Some cleaners are designed to be used with warm water. I hate reading instructions like most people, but there is good information on that label worth knowing.
So, this article contained a fair amount of chemistry, probably more than most of you would have liked. If you read this far, thank you for hanging in there and I hope you learned the most important aspect of car cleaning product chemistry – there is no single product that will clean everything.
The variables are too great. Differences in stain chemistry are significant and require a product “designed” for the job. This by definition limits what a cleaner will work on. (For example, you cannot make a cleaner that is both an acid and a base at the same time.)
And you want something that leaves little or no odor. If it does leave a scent, it needs to smell good. Plus, the spot remover should not eat the skin off your fingers or damage your car surfaces! The list of requirements for a cleaner is larger than most of us realize. All these are limitations, and they make it almost impossible with today’s technology to make one cleaner to rule them all.
However, it is not as bad as it might sound. We can group stains together (e.g. protein based) and that allows us to minimize the number of cleaners we need to keep on hand. So don’t despair, you can get a kit, like this one from Renown. With a kit like this, you don’t have to lug around dozens of bottles and you will be able to banish just about any stain you car is likely to see.
Thanks for reading and Happy Detailing!