From the zaino site:
Cleaning with Clay
Every car finish shares a common enemy: pollution. It relentlessly pursues your car from the second it leaves the factory until your car meets its ultimate demise. It's in the air we breathe, it's on the roads we drive, and it attaches to your car's paint, where it bonds and begins a process of oxidation.
When contaminants get a solid grip on your car's paint, washing alone may not be enough to remove them. Pre-wax cleaners also may not be able to exfoliate large particles. In this case, you have two choices: use a polishing compound, which removes a lot of paint material, or use Z-18 ClayBar. Clay isn't a polish or a compound, it is a surface preparation bar that smoothes the paint and exfoliates contaminants.
USES FOR CLAY
Clay is not a cure-all or a replacement for polishing. It's a tool for removing surface contamination. One of the many reasons for using clay is the removal of brake dust. Brake dust contamination, which attaches to painted rear bumpers and adjoining surfaces, is a metallic surface contaminant that can be removed safely and effectively by using clay.
Clay is also very effective on paint over-spray. If the over-spray is particularly heavy, you may want to seek the assistance of a professional. Tree sap and tar specks can also be safely removed with a clay bar. Recently, I have also started using clay on my windows (exterior) to remove heavy road film, bug deposits and water spots. It works very well, and seems to outperform even the best window cleaners.
EVALUATING YOUR PAINT FOR CLAY
How do you know if you need to use Z-18 ClayBar? After thoroughly hand washing and drying your car, stretch a piece of saran wrap over your hand extending past your fingertips. Gently slide the saran wrap across the finish of your vehicle. Does the surface feel bumpy or gritty? These bumps are contaminants attacking the finish of your car. Removing these surface contaminants (rail dust, road tar, bug residue, paint over-spray, brake pad dust, hard water spots, etc.) will improve both the look and health of your car's paint.
No matter how well you hand-wash your car, many of the contaminants that have worked their way into your car's paint finish will remain. Have you ever looked at your applicator pad after applying a coat of polish? What do you think that black stuff is? It's dirt, and you're sealing it in.
USING THE Z-18 CLAYBAR
Before using a Z-18 ClayBar on your car, you must thoroughly clean and dry your car to remove any loose dirt. Direct sunlight should not fall on your car's surface, and it's best if the work area is relatively cool to prevent rapid evaporation of the clay lubricant.
To use the clay bar, you spray a water-based lubricant (1/2 a cap of Z-7 Show Car Wash with 16 ounces of water) on a small area of your car and rub the bar back and forth with light to medium pressure. Z-18 ClayBar should glide across your paint like a hockey puck on ice. If the lubricant begins to dry, and the Z-18 ClayBar begins to drag, you'll need to spray more lubricant. Clay is fairly sticky, and cannot be used dry.
After a few passes with the ClayBar, rub your hand over the area to feel if the surface contamination was removed. Keep rubbing until all contamination bumps are gone. Finally, wipe the clay residue off with a soft terrycloth towel, and buff to a nice luster. Just like waxing, work in small areas.
Check your Z-18 ClayBar frequently for hard particles. When found, pick them off. Make it a habit to occasionally knead and reform the bar so that a fresh portion of the bar contacts your car's paint. If you drop your bar of clay on the ground, it's history. Toss it out. Don't take any chances, discard the clay bar if it becomes impregnated with grit. Read the manufacturers' directions for the number of uses of their clay bar. Do not overuse a clay bar.
When you're finished claying your car, you should wash it with Z-7 Show Car Wash to remove the lubricant film. Finally, polish and seal your freshly cleaned paint with your choice of Z-2 Show Car Polish for Clear Coated Car Finishes, Z-3 Show Car Polish for Non-clear Coated Paint, or Z-5 Show Car Polish for Swirl Marks and Fine Scratches enabled with ZFX Flash Cure Accelerator Additive.
