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There is a big debate going on amongst detailers over what chemicals to use when hand washing cars. Some purists follow the principle of using chemicals for what they were formulated to do. For example, carwash shampoo is used to wash the car; engine degreaser is used to degrease and clean the engine; carpet shampoo is for the carpet, and so on. Others believe that if a chemical works, then it should be used. So, they will use degreasers at different dilutions to clean the engines, wheels, vinyl, carpets, etc. Some of these same detailers will do the same thing but will use a dishwashing detergent to hand wash the cars. But, I am here to tell you that doing so is a very bad idea.
Good for hands, but bad for clear coat finishes
Dishwashing detergent makers claim that their products “soften hands while you do dishes.” Others promote the ability to remove grease with one drop, and others will say that they can provide dishes with a spot-free shine. Hearing this, is it any wonder that so many consumers — and unfortunately detailers — think it is safe to use dishwashing detergent to wash an automobile?
Chemical experts will point out that dishwashing detergents are a very poor choice for today’s clear coat finishes. Not only should detailers not use dishwashing detergents, they should inform their current customers of the harm that these detergents can do, not just to the paint, but also to the wax as it can strip off the wax protection that they just paid for.
Read on to find out the top seven reasons why washing cars with dishwashing detergent is dangerous to a vehicle’s finish. The reasons include a lot of scary words, like “spotting,” “rust” and “corrosion,” and they should be enough to deter even the most determined dish soap user. This article can be used to educate customers on why they shouldn’t wash their vehicles with dish detergent as well. Hopefully, it will generate repeat customers who will be convinced that it takes more than the soap in their kitchen to get their cars clean.
There are many detailers who will disagree with what I have to say and contend that dishwashing detergent works just fine for them when hand washing cars. But, that’s like saying you can use dishwashing detergent in the shower or for washing your hair. It will still work, but at what cost to your skin, scalp, and hair?
Reason #1: Water softeners and water spots
Manufacturers of dishwashing detergents assume dishes will be hand dried, and many detergents do not contain water softeners that will prevent spotting. Using dishwashing detergent on an automobile increases the likelihood of water spotting. A car will look shiny and clean at first, but the spots will appear soon after, much to the disappointment of the car owner.
However, most carwashing products contain ingredients that soften the water, which helps in preventing water spotting.
Reason #2: Grease cutters
Dishwashing detergents are generally made with certain surfactants which are designed for grease cutting and removal. However, these surfactants can strip off silicones and waxes on a vehicle’s surface. The surfactants will also strip any protection on bare metal parts of the vehicle, such as the engine compartment or the areas inside the doors. This can promote rusting when the detergent finds its way into these areas. Just as well, any chipped spots on the paint are susceptible to corrosion.
The end results are a dull, unprotected finish and the possibility of corrosion in undetected places.
Carwash shampoos are formulated with surfactants that are gentler to the car’s surface in that they do not strip the car of wax or sealant protectants applied to maintain a glossy and protected finish.
Reason #3: Emollients
Dishwashing detergents often contain cosmetic chemicals or emollients to keep hands soft and prevent the cracking and drying that can occur when immersed in water for too long. It’s nice for the skin, but not as nice for the car. These emollients will make a vehicle finish difficult to dry and/or leave it with a smeary appearance and dull finish.
Carwash shampoos do not contain emollients or anything that would be a cosmetic “perk.”
Reason #4: Surfactants
The surfactants found in dishwashing detergent can produce foam that is thicker, denser, and often will not rinse as well as traditional carwash shampoos, which can certainly be a huge problem and a waste of time while washing a car. On top of that, because dishwashing detergents may not completely rinse off, the vehicle may end up with water spotting or a smeared finish.
The surfactants added in carwash shampoos give a thicker, stronger appearance to the product, since “no foam” is often misconstrued as a weak shampoo. However, the surfactants used in carwash shampoos are not the same as surfactants used in dishwashing detergent and will rinse easier.
Reason #5: Dirt removal
For the most part, the surfactants used in dishwashing detergents are not the same as those used in carwash shampoos, as mentioned above. Surfactants used to remove food residue and grease from pots, pans and plates are not the most effective surfactants to remove dirt and oil film from a vehicle. The surfactants used in dishwashing detergents can leave dirt and oil film behind, causing you to work harder having to wash the vehicle more than once.
The surfactants used in carwash shampoos are specially formulated to remove both dirt and oil film.
Reason #6: Additives
Dishwashing detergents contain no special additives. However, well-formulated carwash shampoos contain special additives that provide benefits for hand carwashing. For example, a small amount of high pH additive helps to more effectively remove the dirt and road film and to neutralize any acid rain spots that are on the vehicle. These additives are not contained in dishwashing detergents.
Reason #7: Table salt
Sodium chloride (table salt) is commonly used as a thickening agent in dishwashing detergents to give them the appearance of a quality product. Washing a car with dishwashing detergent is literally like using salt water. This can result in severe water spotting and the promotion of corrosion.
A good quality carwash shampoo will not contain salt to thicken the product.
R.L. “Bud” Abraham is president of Detail Plus Car Appearance Systems, Portland, OR, and a nearly 40-year member of the car care industry. He is also the executive director of the International Detailing Association and a member of the Western Carwash Association Board of Directors. Abraham can be contacted at firstname.lastname@example.org.