From a Phaeton forum on the subject of jet washing:
"Remember that a pure fluid does not clean anything, really. The molecules of paint don't flow with the water (fortunately). This means that what is happening is that you can consider the fluid as a huge flow of tiny microscopic marbles that deforms and flows as the marbles roll one on top of the others (this is why it is a fluid, an not a crystal, where molecules are arranged in a permanent way and cannot move one with reference to the other).
So, at a microscopic level, molecules of paint don't move (they are crystals) but the first layer of H2O molecules that are in direct contact with the static molecules of paint don't move either. There are very strong molecular bonds between two adjacent molecules, and since H2O molecules can move slightly one with reference to another, it is much easier to get the second layer of H20 molecules to move than the first layer that is in direct contact with the paint. So the second layer that is in contact with the first layer of H20 molecules moves just a bit more, but not much either. This continues, and the further away you are from the first layer, the added movement of all the layers means that molecules that are 1mm away fom the surface of the paint move nearly freely wrt the molecule paints.
This means that if you look at the horizontal speed of molecules depending on the distance they are from the paint layer, you will get what is called a positive gradient.
Distance from solid
^
|...........................................................................o.
|..............................o..............................................
|............o................................................................
|....o........................................................................
|.o............**............................................................
|o...........**** <- speck of dust..................................
+-----------**--------------------------------------------------> speed
As a result, you see that if you have a tiny speck of dust, it will barely be affected by your jet wash, since at its level, whatever pressure you will be using will not result in molecules of water moving fast next to it to remove it.
The best demonstration of this is fan blades. Did you notice that fan blades always collect very fine dust on them, even though they should be clean since they constantly move in a flow of air ?
What all this boils down to is that you don't clean anything by using a jet wash. You only remove the larger pieces of crud that are large enough to be taken away by molecules of water that are sufficiently far from the paint to move fast enough and with enough force to remove them.
After you have jet washed your car and let it dry, if you run your finger on it, you should find that a very thin layer of dust will remain. It is physically IMPOSSIBLE to clean off everything with a jet of fluid since the first layer of molecules in contact with the paint doesn't move.
The only solution is mechanical action, like using a sponge. At a microscopic layer, the molecules of the sponge will effectively scrape (and mutually remove) molecules of paint. Unless particles are stuck on the paint, giving an (even gentle) sponge wipe WILL remove far more than the highest pressure jet wash you could use.
So the recommended cleaning products are... a bucket, a sponge and water. Make sure your sponge is really dripping so that when you pass it over the paint, enough lubricant (water) is present so that the dust particles that are removed by the sponge don't scratch the paint.
In order to help the process, you can add some tensio-active molecules (soap) that will bond on one side with oily molecules and on the other side with water molecules. With soap, crud will adhere to the water more than to the paint, so if you wipe the oil-soap-water away, the paint will be left clean.
So usually, I squirt some liquid soap in the bottom of the bucket (not much is needed), fill it up with water, dip my sponge in it, and while pressing on the sponge, gently pass it on the paint. You will see that you don't need many buckets to clean even a large car as a Phaeton, so you save on water.
Finally, you can rinse either with a garden pipe or by throwing some buckets of pure water on the car, starting with the roof.
Then, don't forget to dry the car with some kind of water absorbant matter (I still use doeskin). If you don't do it and if your water is a bit hard (contains dissolved limestone) drying drops will leave white marks on your paint.
The result of a gentle mechanical wipe will be much better than anything you could achieve even with a high pressure jet, which is *very* aggressive on the car as it will push water in all nooks and crannies, locally deform the surface and possibly cause damage (buttons on the door handles of keyless entry cars).
P.
Ps: Spraying your car with foam or soap will help the jet-washing process as it will get soapy water to adhere to oily molecules, so rinsing with the jet will allow to remove smaller specks of dust than if you didn't use any soap at all, but once more, this won't be as thorough a cleaning than with a mechanical action.
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Topic: Waterless wash/wax (Read 1584 times)