Before actual painting begins, it is essential that you prepare the surface for the paint by removing all traces of wax, grease, oil, and dirt. If the paint on the vehicle is of poor quality or deteriorated, remove it. In

Figure 8-67.- Metal shrinking process and sequence used for large areas.

this final preparation of the body before applying paint, you have several methods to choose from. The method that is selected depends on the condition of the existing paint, the equipment available, and the quality of the desired finish product.

If the paint on the vehicle is in good condition (good adherence and without surface defects), go over the surface with a disc sander. An open-coated disc of No. 16 to 24 grit is recommended. This will remove most of the old finish down to the metal. Follow this with a No. 50 close-coated disc to remove any scratches.

If the paint is to be removed from only a portion of the panel, taper the sanded area down into the old paint to produce a featheredge. Follow-up with ,a 150 grit paper in a block sander, and complete the featheredge by water sanding using wet or dry paper of 280 or 320 grit.

NOTE
Some manufacturers of abrasive paper advise different grits with variations of the above procedure. Follow the instructions of the manufacturer.

For removing paint from the entire vehicle, sandblasting is the preferred method. Among the advantages claimed for sandblasting method are speed, low cost, and a surface that has good paint adherence.

After removing the old paint, clean the surface with a cleaning agent. If none is available, a lint-free cloth saturated with paint thinner can be used to wipe down the surface. This will help the new paint to adhere to the metal and remove the dust and other foreign matter.

Apply the primer coat as soon as possible after the paint is removed. This is particularly important when the surface has been sandblasted, because the surface is practically in a raw state and quickly starts rusting.