confused on ph scale for soaps

I

III

97 bonneville/98 Z71
I've used Dawn dish soap for years for cleaning my foam pads and other items. I called the company because I was curious to see what level on the ph scale Dawn is. I was told that the regular Dawn is a 8, while Dawn complete is a 9.

This confuses me a little because I fully understand not to use household soap for washing vehicles, and I never have, nor do I plan to. I've been told that Meguiar's Gold Class car soap is also a 9 on the ph scale. This is where I'm confused. If Dawn has a ph of 8 or 9, and an automotive soap has a ph level of 9, why is it bad to use the Dawn on your paint? Has this nothing to do with the ph of each product, but it's the ingredients of the product?
 
I dont see how infrequent use of Dawn, especially once a year, can damage paint. this is always a controversial topic.
 
III, you have raised an interesting question. Perhaps it has been addressed before, but I don't recall the response. Hopefully someone will come along and enlighten us all.
 
Carwashes typically use alkaline (pH 9-10 max) presoak chemicals because of their effectiveness on organic soiling such as bird droppings, sap etc. High pH is used in waste treatment to separate fat and oils from water before skimming the risen fat and oils from the waste (usually greasetrap waste). Low pH (acids of course) clean glass very well, neutralising calcium salts (water marks) and can break down oils as well. Detergents on the other hand I believe work through polar and nonpolar properties of long hydrocarbon chain chemicals with sulfate groups attached. These molecules surround nonpolar molecules of dirt, grease and oils etc that are not soluble in water. Soluble dirts are treated by changing the pH of the water to force the dirt to 'fall out' of the solution. I.e. acidic solutions inhibit calcium, iron and magnesium from dissolving in water. These elements and their compound salts are readily soluble in higher pH's hence the difficulty cleaning a car using hard water.

Maybe there's a chemist amoungst us that can correct me.
 
Oh yeah, since paints contain essential oils and oil and water don't mix, the binding action of detergents on these non-polar oils in the paint would be disasterous for paint. Don't believe me that detergents are tops at removing oil from water? Then you might want to wash your baking tray on it's own in the sink. The rainbow of oil in the water quickly dissappears when the detergent is added and splashed around. But the oil isn't gone, its just wrapped in a detergent molecule ball. Take a clean drinking glass and take a scoop of the washing water, hold it up and look. Mirky isn't it? But there's no oil slick on the surface. Isn't chemistry great ;)
 
I think I read somewhere the dishwashing liquid is particularly bad on the plastic part of the car (the rubber seal etc)and not so much damage on the paint.
 
Even on the Dawn website They tell you
Ok to wash car?

Question
Can I wash my car with dishwashing detergent?

Answer
Your car surface and the dirt that gets on it are a lot different from the food soils and dishes that dishwashing liquids clean effectively. We don't recommend them for cleaning your car.
Click to expand...
 
I'm sure that's all true but once a year, on the paint only for several minutes probably won't do anything. Environmental conditions the car is exposed,probably most likely acid rain could do more damage. I wonder instead of Dawn, maybe using Prepsol after using a regular wash would give the same results everyone wants from using Dawn.
 
EZ Boy said:
Carwashes typically use alkaline (pH 9-10 max) presoak chemicals because of their effectiveness on organic soiling such as bird droppings, sap etc. High pH is used in waste treatment to separate fat and oils from water before skimming the risen fat and oils from the waste (usually greasetrap waste). Low pH (acids of course) clean glass very well, neutralising calcium salts (water marks) and can break down oils as well. Detergents on the other hand I believe work through polar and nonpolar properties of long hydrocarbon chain chemicals with sulfate groups attached. These molecules surround nonpolar molecules of dirt, grease and oils etc that are not soluble in water. Soluble dirts are treated by changing the pH of the water to force the dirt to 'fall out' of the solution. I.e. acidic solutions inhibit calcium, iron and magnesium from dissolving in water. These elements and their compound salts are readily soluble in higher pH's hence the difficulty cleaning a car using hard water.

Maybe there's a chemist amoungst us that can correct me.
Click to expand...

Pretty good answer EZ Boy. It's about 90% correct, but here's a few points. Acids won't break down grease/oils unless they are saponified AND normally are soluble. On detergents, sulfates are most common but other groups such as phosphates are used as well. You want dirts to dissolve into solution not fall out of solution. A great example of falling out of solution is a hard water spot. You are correct that changing pH is one way to accomplish this. Acidic solutions enhance calcium, iron, and magnesium dissolution, such as the product CLR. Hard water just has high levels of these heavy metals and thus they bind stronger to anions and precipitate out leaving "spots". You have the right idea at the end, you just reversed your terms.

Okay that said, while some may find tech talk interesting most are probably saying, "what the hell does it mean? get to the point". Here's the take home point on pH:

Soaps clean by two actions- Chemical (pH) and Physical (abrasives, detergents, emulsifiers, surfactants, chelators (one could argue chemical for chelators as well)). Dawn and Meg's both have a slightly alkaline pH along with Simple Green. So the difference must be in the detergents and sure enough it is. Dawn contains harsher detergents like SDS which STRIP oils where as Meg's are much less aggressive. Stripping oils from paint reduces the protection from oxidation and your paint will start to rapidly oxidize. Clears are less affected. Same for plastics except add plasticizers which make the plastic flexible are removed which cause stiffening of the plastic, brittleness, and cracking.
Hope this helps.
 
Will all of that happen in one wash once or even twice a year? How about the use of Valugard's ABC wash system or Finish Kare's equivalent on new cars for prep? I think those washes are even harsher than Dawn. If the Dawn really should be avoided at all costs, how about using Prep Sol to ensure all residual waxes and sealants are removed from the paint prior to polishing?
 
rhillstr said:
Same for plastics except add plasticizers which make the plastic flexible are removed which cause stiffening of the plastic, brittleness, and cracking.
Hope this helps. [/B]
Click to expand...

The damage that it could do to the plastic or rubber is enough to stop me from using dishwashing liquid.
 
And that is the heart of the debate. Many claim they use it without harm, like many smokers don't feel they are hurting themselves in the beginning. Like smokers many claim they only do it "once in a while" so therefore it cannot hurt. Like many things there is a safe point where you could get away with the indiscretion. The question is where and how much? Like smoking the question is unanswered so the universal advice is: DON'T DO IT. Yes it's more or less a copp out.
As for your cleaners, I am not familiar with them but if they are new car preps I assume they are for one time use since a car is only new once or are they used everytime a car is prepped for sale (ie new and used)? I seriously doubt one exposure would hurt the finish but repeated exposure would. I would also try to counteract the damage by using a polish or All-in-one type finish that had the ability to replenish essential oils to the finish. Also clears (on all modern cars) are MUCH more resilient and resist this type of damage better as well.

Lastly- Polishing removes residual wax/sealant so you don't need special stripping steps- it's a sales ploy to sell products.
 
True but one line of polish that actually contains wax is the 1z polishes, if one wants to see exactly what defects need to be removed, an isopropyl alcohol mix ( or the prepsol type cleaners) would be needed, other wise topping them with a traditional wax would be just fine as a last step
 
Poorboy's Polish with Carnauba also contains wax but if you're prepping a surface for detail and oxidation, scratches, and swirls are needing correcting you would not use a one step prep like 1Z or PWC. They are best used on a car that needs minor swirl correction and to restore the shine to the paint, preferrably on a car that was previously detailed within the last year. Also, they do not lay down much wax unless you let them dry before buffing them off.
 
Thanks rhillstr, its been a long time since I've done any chemistry, I was meant to be a sales manager for a soil testing lab in a past life. Time for a refresher I think.
 
1z is not one step, I'm referring to its line of three polishes: Ultra, Paint and Metallic polish, these cn be used on cars in various degrees of shape, by rotary if the defects are bad.
 
He he, :o yeah, this is getting long winded especially since we added discussing polishes into the mix.
 
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