Article 22 Final Paint on the Body Shell
In the last installment of my restoration of an E-type, I had completed the application of the final paint on the bodyshell. I used a “two-stage” paint, where coats of color are applied first and then coats of clear are applied last. This is also commonly known as “basecoat/clearcoat” and is a very common methodology with the paint systems on today’s new cars, especially high end models. The basecoat can be optimized to provide excellent coverage over the primer and the perfect desired color. The clearcoat can be optimized to provide a great shine and durability. The other option is a single stage paint, which combines the color and the clear in one product. This is not a bad way to go and may prove to be a little cheaper. The range of colors available will tend to be more limited. In either case, modern single stage and two-stage paints are predominantly urethane based. The older enamel and laquer based paints are very difficult to obtain anymore in automotive grades.
Whichever way you or your painter go with, I highly recommend that after the paint is applied that you finish up with a sanding and polishing step. This step goes by several names. One is “color sanding”. Another is “cut and buff”. What you are going to get is the best possible appearance to your paint job.
If we were to look at any paint job under magnification, we would see that the surface is not flat but rather contains peaks and valleys. This irregular surface reflects the light off at crazy angles such that the paint doesn’t shine as well as it could and reflections of objects are distorted. What you are going to do is “cut” the peaks down until they are at the same level as the valleys, leaving an extremely level surface. Like Kansas! Then you are going to “buff” that surface to a brilliant shine.
In my case, I didn’t need magnification to see the peaks and valleys. My application of clearcoat contained a generous dose of “orange peel”, which takes it name from the granular surface of an orange. There are several reasons why orange peel occurs. In my case, my fear of laying the paint on so thickly that runs would develop led me to spray the paint too lightly, causing it to dry in peaks and valleys before it could naturally flow out to a more level surface. This was a necessary outcome due to my inexperience but, as we will see, one that the amateur painter can recover from.
If you know you are going to be cutting and buffing, be sure and apply several extra coats of clear, so that you have plenty of surface to work with. Cutting can begin as soon as 24 hours after the clear is applied. In general, the sooner you get started the better. The chemical reaction that hardens the urethane paint takes place over several weeks. If your were to wait say a month to begin cutting, the process would go much slower due to the hardness of the paint.
If you are doing this for the first time, you might want to start on a smaller part like a door or even a scrap item that you paint for this purpose. Bad stuff can happen, like cutting through the clearcoat. A little practice can help build confidence in the process.
The first step involves the use of modern ultra fine grit sandpapers. These sandpapers come with number rating like 1000, 1500, and 2000. This is compared to the paper you may have used to sand wood, which runs in the range of 60 or so. Although the work can be done by hand, I highly recommend a random orbital sander. In the air driven variety, they come as “palm sanders” as they fit into the palm of your hand. The sandpaper attaches with velcro and floats on a foam base. At this stage, I recommend “wet sanding”, which just like it sounds involves the application of water as you go. This will flush away sanding dust and the odd bit of debris as you go. I use a squirt bottle to keep the surface moist. If you have bad orange peel like I did, you might start with 1000 grit paper. As soon as you begin wet sanding the existing shine will go very dull. Don’t panic, this is normal. After a few minutes work over say a 2 foot square area, stop and dry off the surface. In fact, the peaks will be dull but the valleys will still be shiny, since the sandpaper hasn’t worked its way down to them. As your surface becomes mostly dull with a bunch of shiny specs, switch to 1500 paper. You can even finish up with 2000 or 2500 paper, which will reduce the amount of buffing required. You are done when the entire surface is dull in appearance. Be careful to stay away from edges and folds, as you can cut through the clear to the color coat very quickly at these locations. Edges and folds can be carefully hand sanded or maybe just left as is. Note that wet sanding process can also be used to work out minor paint defects that reside near the surface of the clearcoat, like dust particles and insect parts.
The next step is the buffing step. This is most efficiently done with a buffing machine, although it can be done by hand also. I use an electric Makita that has a variable speed capability. Mounted on the buffer is a flat disk, again with a Velcro face, to which various pads are attached. Normally a wool pad is used for initial buffing, using a liquid buffing compound. The liquid buffing compound is a form of sandpaper. Within the creamy liquid there is a suspension of fine abrasive particles. These particles will serve to knock down the very fine scratches left behind from the wet sanding paper. The buffing compound is spread over the paint surface and worked with the wool pad, following the instructions on the bottle of compound. After the initial buffing, you will immediately see a big improvement in the shine. Note that this same process is used to rejuvenate older paint finishes that have dulled and is indeed referred to as “compounding”.
The final step is the polish step. This is performed similar to the buffing step. A foam pad is mounted on the buffing machine and the polishing paste is spread over the paint surface. Follow the instructions on your bottle of polish as to the speed setting for the buffing machine. When you are done polishing your paint surface will have a deep brilliant shine and, if you are like me, you will feel an immense feeling of satisfaction and accomplishment!
No comments yet.