Color Sanding And Buffing - Good Reflections
How To Cut And Polish To A Perfect Finish
From the June, 2009 issue of Corvette Fever
By Steve Dulcich
Photography by Steve Dulcich
After all the tedious stripping, bodywork, primer-blocking, and then laying down the paint, the true reward is only gained after the cut and polish is completed. In the old days, the process was called burnishing, and it meant taking an abrasive to a surface until perfectly smooth and flat, and then polishing it to a mirror finish. In the world of custom automotive finishes, the cut and polish job is the route to those show-stopping paint finishes that are the envy of all.
Although it takes considerable skill to achieve a beautifully polished paint finish, it's a skill that can be quickly mastered by those willing to put in the effort. The list of equipment required is relatively short, with the only specialized item being the paint buffer itself. As the terminology implies, a cut-and-polish effort is really two separate tasks, the first being to sand the freshly cured paint, followed by the polishing process.
It might seem drastic to take sandpaper to that gleaming fresh paint, but that's just how the job begins--with wet-sanding of the surface. Specialty sandpaper of a very fine grit is used, which creates sanding scratches of minimal depth so that they can be polished out in the buffing process. There's no question that a variety of paint sins can be improved by the cut-and-polish process, but it holds true that the better the quality of the finish "off-the-gun," the better the final results. Ideally, we would recommend the finest paper practical for the sanding process, but if the finish is showing fairly heavy texture, or "orange-peel," beginning with a coarser paper may be the only practical choice. Generally speaking, 1,000 grit is the coarsest normally used for wet-sanding the finish, while 1,500 is the norm, and as fine as 2,000 grit is preferred by some.
Clockwise from the lower left...
Clockwise from the lower left are the supplies required to cut and buff a paint job like a pro. Youll need sheets of wet and dry sandpaper, usually between 1,000-2,000 grit, hand blocking pads and/or sanding blocks, a sponge (along with a bucket) to supply the water, cutting compound, and polishing glaze.
During the sanding process, it's important to keep the surface wet and cleared of sanding debris. An ample supply of water is required, most commonly supplied by a large sponge and bucket. Use a small amount of dish soap in the water to help lubricate the surface, and work the sandpaper in long, consistent strokes. To improve leveling, it's advisable to use a flexible hand pad, or block, to back up the sandpaper, rather than working the surface by hand. The objective is to get a perfectly smooth and flat surface, devoid of any gloss. It's impossible to tell if the paint is sufficiently sanded while the surface is still wet since the water will impart a false gloss to the paint. The procedure is to sand, wipe dry, and check, and then sand some more or move on.
Polishing is the process of bringing back the luster and shine of the paint, which has been made dull by sanding. To do so the surface of the paint is evenly polished down until all the surface is below the level of the sanding scratches and perfectly smooth. Although many painters have their own favorite techniques, processes, and materials, the most common approach includes two steps: a coarse rubbing-compound cut, followed by a fine-polishing compound or glaze. The compounding cut is usually done with a coarser-texture pad on the buffer, and the objective is to remove the bulk of the sanding scratches, quickly taking the paint down to a relatively smooth shine.
The aggressive action of the compound, however, isn't fine enough for the brilliant and smooth show-car finish we're after and typically shows distinct swirl marks in the paint surface. To correct this, we have a second stage of the polishing effort. The finishing compound, or glaze, is a much finer compound and removes a minimum of paint material, while polishing the surface to a brilliant shine. Normally, a much finer polishing bonnet is used for this step. Follow along as we work through all of the cutting and polishing steps on our recently painted aftermarket L88 hood.
|Difficulty Index - 3 Wrenches|
|Anyone's Project: no tools required||1 Wrench|
|Beginner: basic tools||2 Wrenches|
|Experienced: special tools||3 Wrenches|
|Accomplished: special tools and outside help||4 Wrenches|
|Professionals Only: send this work out||5 Wrenches|
Step 1 is to cut the paint...
Step 1 is to cut the paint surface, usually the clear coat in a modern two-stage paint job. Heavier texture will require coarser paper to correct, though there's no question that the better the paint is laid down in the first place, the better the final results. Usually 1,000 grit is the coarsest used, followed by 1,500 grit to make the polishing easier. We had very nice paint, and went straight to the finer 1,500 grit, using a hand pad.
Clear will sand off in a white...
Clear will sand off in a white slurry, and the surface will show an evenly flat sheen with no shiny spots visible when wiped dry. Here, the side of the hood to the left is finished and evenly sanded flat, while the right side of the photo shows that more sanding is required.
A good buffer is mandatory...
A good buffer is mandatory to achieve good results. Unlike a sander, which operates at high rpm, a commercial paint buffer operates at 1,800-2,500 rpm, depending upon the model. Buff pads are traditionally wool fiber and come as coarse cutting pads (right) and fine polishing pads (left). Foam polishing pads are also in common use, and favored by some technicians.
Paint specialists seems to...
Paint specialists seems to have their favorite brand of compounds. We like 3M brand products, and are using their Perfect-It III cutting compound. Compounding should be done in a well-lit shady area, and never under direct sunlight. Work is done over a small section at a time; here we're applying a ribbon of compound to an area of the hood for buffing.
The technique is to let the...
The technique is to let the operating buffer pick up the compound and spread it over the work area, working the buffer side to side with light pressure. This covers the portion of the panel being buffed with a nice even layer of compound. The buffer is run at light pressure back and forth over the area until the compound dries and works off in a haze.
Edges are a special consideration...
Edges are a special consideration since the buffer can easily catch and burn, or scrape the paint. Always be aware of the direction of rotation of the buffer and how the buffer is tilted, which determines which side of the pad is in contact with the panel. Always make sure the pad is working off the edge. As shown here, the buffer is tilted so that the nose of the pad is the working surface, and the buffing pad is gliding off the edge.
Attempting to cut into an...
Attempting to cut into an edge, as shown by the buffer position here, causes the pad to grab and may quickly damage the fragile paint surface. A mistake here usually requires a return trip to the paint booth.
Once the entire hood is compounded,...
Once the entire hood is compounded, it's noticeably glossier than before, though close examination shows swirl marks from the buffer. The polishing step makes the surface even glossier and removes the swirls. Always wipe the surface completely clean with a wet rag to remove all traces of the compounding dust before changing to a finer compound, since the residue will contaminate the results.
We changed pads to a Schlegel...
We changed pads to a Schlegel number two Buff, a fine-polishing wool pad, in preparation of the final polishing, sometimes called glazing. A foam pad, as favored by some paint technicians, can be substituted here, though the traditional wool pad yields equivalent results.
Applying the glaze (polishing...
Applying the glaze (polishing compound) is just like with the cutting compound, again working a panel one section at a time. Here we're putting down a ribbon of 3M Micro-finishing Glaze.
The final glazing is done...
The final glazing is done with much the same technique as the cutting compound, though the finish buffing is done with a very light pressure, just letting the buffer skim the surface with a slightly faster hand stroke until the glaze is worked off the surface.
This is the kind of paint...
This is the kind of paint finish that makes all the work seem worthwhile.