Clear Coating and Buffing
CLEAR COATING AND BUFFING
by Blair Elliott
The first thing that you should consider when you think about buffing,... is,... "What the heck is wrong with my clear coating that I have to do so much buffing"? By getting better at spraying your clear, you cut your buffing needs down to all most nothing. There are so many variables involved that can make a huge difference in your finish. A few are cleanliness, room temperature, hardener and activator speed, air pressure, fluid tip size, the distance from the spraygun to the target, spray pattern overlap, and working speed.
The sprayguns mission is to atomize the refinishing material,... it takes paint droplets and divides them into thousands of tiny particles which upon hitting the panel, flow into one another giving a nice level finish. To achieve this, a sprayguns set up should be the best combination of the proper nozzle choice, pressure setting, fluid flow and fan width. The fan control is used to control the spray pattern width. As a rule, most painters want to use as wide a fan as possible, but as the fan widens, the amount of material distributed decreases causing dryness.
A slower hardener, or a slower activator combined with cooler temperature will also allow the clear more time to flow out smooth. Your spraying technique also needs to be dependent on constant visual feedback,... you have to watch what you are doing. Be sure to apply the paint evenly,... pass the gun perpendicular to the surface at a constant speed. Slowing the rate of the pass will put more material on the panel, and increasing speed will decrease the amount of material applied. Use the speed to regulate your material, and watch the panel very closely to see if you are "wetting" the surface. Each pass of the spraygun should overlap the previous one by about 50 percent. Watch the material closely to see how it is being laid down. Don't be shy about applying the clear, If you’re afraid to "wet" the panel, you’ll produce a dry-looking paint job with excess orange peel. Remember that runs in the clear coat are usually repairable after they have cured. Most painters (myself included) would rather block sand out a run than have an entire orange peel job. It’s like everything else,... the more you paint,... the better you’ll get at it!
As to buffing... first you need to determine your needs, are you fixing a couple of minor dirt nibs, (some 2000 on a block and a hand rub will do the trick)… or do you have a major orange peel problem. Anything more aggressive than 1000 can do far too much damage, and you run a high risk of sanding through the clear coat, or not being able to remove the deep sand scratches. On the other hand,… paper less aggressive than 2500 is a waste of time, you may as well just compound the area, although finishing the job with 2000 or 2500 paper will mean fairly easy sand scratch removal when it comes time to buff.
You’ll need a soft foam or rubber backing pad so that the paper may be wrapped around this pad (not around your fingers!) The backing pads can be harder or softer depending on what you need to accomplish and how aggressive you want to be with a particular piece of paper. You will also need a bucket of water to keep cleansing the paper. A water bottle (sprayer)is a good idea to keep handy to spray the area as you come upon it. A small rubber bondo squeegee to wipe water away and check your progress is also a good idea to have available, as well as clean towels and an air hose to fully dry an area you want to examine as you finish it.
Keep the paper wet and clean because it will clog with bits of removed clear coat and could cause deeper scratches than the paper would itself. Continue to dip the paper in a bucket of water often. Also keep track of the paper itself. Once it does not cut well anymore, turn it over to a fresh side, or get a new piece of paper. Constantly evaluate your progress. Periodically dry the panel and inspect it. What you are looking for is no gloss and no orange peel at all. If part of the panel still shines, you have missed a spot.
You want to finish the job with 2000 or 2500 grit paper. The sand scratches that these grades of paper leave behind are fairly easy to remove. If you started sanding the car with 1200 paper you need to gradually lighten the grades. You want to eliminate the sand scratches from the previous grade of paper. For instance, if you start with 1200 paper, you will need to go to 1500 paper, and then to 2000 paper. You can't skip from 1200 to 2000. Doing this will not eliminate the deeper sand scratch marks made from the 1200 grit paper. Once you have the entire vehicle finished off in either 2000 or 2500 grit, you can begin the buffing process.
To prevent burns, you need to know how the rotary buffer works. With few exceptions, buffers rotate clockwise. When using a buffer, lift the left side of the buffer slightly (a half inch or so). Move the buffer in smooth left to right strokes. It is best to focus pad contact on the 12 o'clock to the 4 o'clock quadrant (i.e., the right edge when looking at the top of the buffer). In this way, the buffing pad will always rotate off the edge of a panel. The reason for lifting the left side of the buffer is to prevent the trailing edge of the buffing pad from driving into a body panel edge. The trailing edge of the pad driving into a body edge creates so much friction it can rapidly burn through the finish. By rolling the right side of the pad off the body panel edge and lifting the left side, you can significantly reduce the risk of burning.
To further reduce the risk of burning, buff up to edges and body ridges, not on them. When buffing raised peaks or body lines, keep the buffing pad as flat as possible, and slow the buffer speed. Keep the buffing machine moving at all times. If you allow the buffing pad to spin in one spot for more than a few seconds, you're inviting disaster. Other tricks include opening the door, trunk or hood slightly. This gives you an edge to roll off of when buffing. Always slow buffer speed when approaching an edge.
The operating speed of your buffer is very important. I highly recommend using slower speeds. Speeds between 1200 and 2000 rpm are sufficient on most clear finishes. Just remember, slower speeds create less friction, thereby reducing the chance of burns.
Start learning by applying a single line of polish around the edge of the buffing pad. Don't use too much polish, or it will splatter everywhere and take too long to buff out. Before starting the polisher or rotary buffer, lay the pad on the paint surface to be worked and spread the polish around. Once the polish is distributed over the area you're working on, you can begin to increase speed a bit.
Work the polish in well, using overlapping left-to-right and top-to-bottom passes.
Be sure to check your buffing pad periodically, as it will become caked with polish. Use a pad spur to clean it. Lay the buffer across the top of your leg and turn the machine on. Gently press the pad spur into the pad, starting at the outer edge, and run it into the center. Don’t pass that center line or the pad will grab and launch the spur back at you,… it’s pretty easy to injure a thumb or wrist. Foam pads can be cleaned with soap and water. Do not use the same polishing pad or cloth with multiple abrasive materials.
Hmmmm,… well that’s a start anyway,… didn’t cover wool vs. foam,… or different compounds, glazes etc,… but it’s a big topic and not everyone goes about it the same way. I’m sure others will chip in with their thoughts on things I’ve probably missed. The last few years or so I’ve been using the 3M Trizac system,… but that’s another how to.
I'm sure I've missed lots here but you could literally write an entire book on the subject.
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