Drying questions. Distilled water, should I bother, and so on.

[Jreepers]

Hi all,



1) How necessary is drying a car after washing really, especially since it seems that most people don`t dry their car after it rains. Doesn`t rain typically leave water spots too? (I`m just trying to justify spending $20-25 on a good drying towel. )



2) Instead of using a drying towel (anyone like Griot`s yellow MF by the way?), do you think pouring a gallon or so of distilled water over the car and not drying it after would work too since apparently distilled water doesn`t leave any water spots?

[imported_PiPUK]

Rain water is often better than tap water. Tap water will typically start life as rain which hits the land and flows over/through rocks etc. which results in it dissolving minerals. These minerals are non-volatile so when the water evaporates, the minerals remain and leave water spots. I often wash the car in the rain because the rain effectively is demineralised water so it dries to a spot free finish. Unfortunately it is not just as simple as that because a contaminated atmosphere (e.g. dusty desert areas) will have a load of particulate or other matter which would be carried down with the rain and this material will then leave residues when the water evaporates away.



As for the 2nd question, you could use demineralised/deioniser or distilled water, the former will tend to be cheaper but does the job just as well. You would quickly go through a lot of water though!

[Ron Ketcham]

The USA goverment has on their EPA and other websites, one may access, which show that "average" acid rain of the area of most major cities.

That should be enough to determine what is in the rain water that your vehicle is going to have land on it.

Then, and this is every important, what is the average temperature of the area where one lives and the color of the vehicle,(base coat color makes a big difference, it is the one that absorbs the heat, under the clearcoat),when that rain comes in contact with a vehicle.

I do believe that anyone with the least basic knowledge of chemistry, will be able to deal with "heat reactivity" and the basic understand how "heat" will create an expanision of the surface of a "clearcoat" (basically a "plastic substrate"), which will allow the air borne acids to liquifiy and enter the porus paint surface.(heat is what creates the "reactivity of the acids", got it, then the "paint film" is expanded, so it absorbs the acids)

This combination of heat and acids particles, being they are now liquid in form, allows them to enter the resins system (film former/binder) of the paint system and start it`s attacking, IE, eating the resin system apart.

And all this time, people read how great a "product" is to protect from "water spots", acid rain, etc and here you just read the facts, with no "buy this" hype.

[Dan]

As stated, rain water is essential distilled water. Spots happen from dirt and pollution. What sort of waterspots are you looking to avoid?

[Ron Ketcham]

As stated, rain water is essential distilled water. Spots happen from dirt and pollution. What sort of waterspots are you looking to avoid?

Dan, not so, in my work with the paint suppliers, the car maufacturers, etc, for over several decades, testing of "rain water" in various parts of the country, have shown that "rain water" , major metro areas, where there is heavy industry, refinery operations, large vehicle populations, there is the "acid rain" thing to consider.

An example, when I was still working, in LA, the average rain fall was 2.5 on the pH scale, when I was in Cincinnati, in the early 90`s, the pH of rain could be at that level or less, but could average out at 3.5 pH.

That is "acidic" in any one`s book.

This is the problem that must be take in to consideration when addressing "water spots".

Some may live in areas that do not have high acidic rain fall, but they may also be close to industry such as paper mills, refinery`s, etc.(then there is the direction of the wind and such, how it may carry into a valley, etc and become stagnet, allowing the particle to drop from the atmosphere and land on surfacews)

In those, where they live in close by areas, they may go as low as 2 on the pH scale.

Where you are, the level may only be 5 or 6 on the pH scale, however, other`s may be experinceing pH levels of 3.5 to down to 2 on the pH scale.

The level may be due to sulfuric emissions, nitric emission, etc, all will create a damaging effect on paint, just that some require more temperature or heat, or such to make it possible for them to eat at a vehicle`s paint finish.

[imported_PiPUK]

Ron is right... this isn`t something I have ever encountered but Ireland isn`t exactly heavily industrialised!

[Dan]

Both of you propeller heads are taking this a bit far. The OP hasn`t stated what sorts of spots he`s getting. Every water spot isn`t acid rain or pollution based damage. Especially if he uses a good LSP.

[imported_PiPUK]

I think the OP is having problem with wash water which will have dissolved minerals. The debate with regards to the rain is because he asked for the comparison between rain and wash water - I think between the two of us, we have covered the most important points in this.

[Accumulator]

Hi all,



1) How necessary is drying a car after washing really, especially since it seems that most people don`t dry their car after it rains. Doesn`t rain typically leave water spots too? (I`m just trying to justify spending $20-25 on a good drying towel. )

How hard/soft is the rinse water you`re using? My water is very soft, but it still leaves spotting/deposits on the car..not nearly as bad as "hard" water does, but bad enough that I`m not satisfied with just blowing it off with my AirWand and compressor (and they get >90% of the water off).

2) Instead of using a drying towel (anyone like Griot`s yellow MF by the way?), do you think pouring a gallon or so of distilled water over the car and not drying it after would work too since apparently distilled water doesn`t leave any water spots?

I sometimes use my deionizer for the final rinse, and no matter how thoroughly I rinse the vehicle with it I still get some spotting from "regular water" that was trapped in the nooks and crannies. Minimal, but I do get some. No way that just dumping a few gallons of distilled/DI water on it would do the job. Only way to avoid this is to meticulously blow said water out with the compressor and dry it up with my drying towel. IME it`s *barely* worth using the deionizer....worth it to me on some vehicles, but I`d stop short of recommending that others do it unless they`re dealing with really crappy water quality or are somehow unable to dry "properly" and just want to mitigate things a bit.



IMO it`s just a matter of how particular you`re gonna be about this stuff. Unless you dry all the water, I`d expect you to get some kind of spotting/rinse-water artifacts.