Real Paint Problems - Paint Rejuvenation
Bring Back Your Old Paint On The Cheap Instead Of An Expensive Repaint
From the January, 2001 issue of Mopar Muscle
By Steve Dulcich
Three days of hard work bringing...
Three days of hard work bringing the paint back resulted in a car far from the shameful sight we started with.
In a perfect world, everyone would drive a classic Mopar, and they would all have flawless show-car paint. But for the average street driver, the real world means real paint problems. With use it's inevitable-a chip here, a ding there, and the progression of time and the elements take their toll. Let's face it, cosmetics can only get worse from where you started unless some effort is expended. Care and maintenance can keep a finish looking good for years, but sometimes we're faced with neglected and hurting paint. The surest cure for problem paint is just wiping the slate clean and starting over with new pigment; but sometimes, at least for the time being, it's not in the cards. It might be a matter of cost (priced a quality paint job lately?), or just practicalities-maybe having the car down for weeks or even months for a repaint just isn't likely when having that car laid up means hoofing it.
Our 'Cuda is an extreme example of neglected paint. When it was shot with quality DuPont Centari acrylic enamel back in 1990 it looked good, but now the ten-year-old paint is trashed. It didn't have to be. Left in the hands of others, it was smacked up front, bodyshop repainted on the front fill panel and fender sides, and then left outside to cook in the Bakersfield sun for two years: "Here's your car back." Thanks a lot.
Though it runs good, this...
Though it runs good, this old Mopar looked like a heap. It will have to wait its turn for a full resto, but we'll at least make it look respectable in the meantime by fixing the paint. We know, the AAR hood isn't correct.
No question; to get it looking the way we want it, a total repaint is in order. But with several resto projects underway, pulling the 'Cuda down for what will be a bare-tub rebuild will have to wait. In the meanwhile, it runs and drives, so it gets used-but going down the road in what looks like rolling junk is getting old. Rather than repaint, the solution for now is to work with what's there and repair the existing paint.
Just about any finish can be made to look decent with some effort and the right techniques. On this car, the basic paint was still sound, but it suffered from a wide range of maladies: chips, scratches, gouged paint, cracked plastic filler, a dented door, and extreme oxidation; all these things can be fixed. Fortunately we didn't have unfixable problems such as blistering, checking, peeling, or puckered paint or clearcoat. We'll go through the problems and the cures, and from junker to jewel.
Step one is a thorough wash,...
Step one is a thorough wash, using harsh detergents in this case to get it clean. The front fill panel and fender sides have been repainted since the last overall paint job, and remained glossy, but the rest of the car was so heavily oxidized it was flat as primer. Here you can also see that the extreme oxidation caused a color shift from red to flat orange.
Fading And Surface Flaws:Cutting
Fading or oxidized paint comes in different degrees, but the cure is always the same: removing the oxidized outer layer of paint to expose a fresh one below. Some colors are more prone to fading than others; red, like on this 'Cuda, is one of the worst. Removing the oxidized layer makes the presumption that the paint is sufficiently thick to get down to good paint without running through it to the primer. Which technique is used for cutting depends on the extent of the problem. Sometimes a mild abrasive cleaner wax and some handwork can do the job. For more serious problems, a cut-and-buff is the serious solution.
Cutting-and-buffing begins with sanding the paint with ultra-fine sandpaper, then buffing the finish to a high polish. To remove minute surface imperfections, most show-quality paint jobs receive a cut-and-buff as the final step to that glass-smooth finish. Sanding is done by hand and has to be done wet, which keeps the sandpaper from loading up and clears the debris from the surface being worked. Generally, 1500-grit paper is used because it removes the surface and leaves sanding scratches fine enough to be machine-polished out. A foam hand-sanding pad backs the sandpaper strip.
Sanding can be ruinous if certain mistakes are made. First is the cut-through. Obviously, if the color coat is sanded too far and you've gone through the paint, or even made it too thin, the primer will show through. Use care around any edge or character line, since the raised edge will cut-through easily. Solid colors and clearcoats lend themselves to cutting, but non-clearcoated metalics can present problems.
The first process to bring...
The first process to bring back extremely oxidized paint is wet sanding (1500-grit here), which preps the surface for paint repair and cleans and smoothes it for the buff-out. A hose, sponge,or bucket will work. The bright trim has been taped off to prevent scratches. Mirrors, emblems, and the fender-mounted turn signal indicators are removed.
Though hard to see in a black...
Though hard to see in a black and white photo, sanding exposes the original red, as seen on this fender top. It works like a guidecoat, as we can see the surface clear up as we go.
The chips are filled with...
The chips are filled with spot putty to bring them level with the surface. A small piece cut off a plastic Bondo spreader helps apply the putty with precision, which is vital for a successful repair. Don't overfill the area.
Spot putty on the various...
Spot putty on the various chips and gouges is sanded back with 400- or 600-grit paper, depending on the size of the spot.
The biggest problem was a...
The biggest problem was a bent-in door edge. To fix it, the door had to come off.
Some hammer and dolly work...
Some hammer and dolly work bangs the edge back into shape.
This quick repair needs some...
This quick repair needs some filler. The area is quickly stripped with a 3M Clean and Strip wheel and then feathered with a D/A.
Metalics get the metallic effect from small particles in the paint. Sanding can disturb the metallic particles in a visible pattern, and it won't readily buff out. Dark metalics are more sensitive than light ones to this phenomena. If the paint is burned out with oxidation, there may be no other alternative than to try an area and see if it will sand and buff out uniformly. Using the finest paper available reduces the chances of streaking the metallic in the sanding process.
None of the original factory musclecar paint jobs were clearcoated, but for a number of years now, clearcoating has become routine. Clearcoats cut-and-buff well, but if the clear is cut-through and the paint is exposed, the hole will be visible a mile away. Even respraying clear over the cut-through won't hide it, since the underlying basecoat will always shift color when disturbed. Our 'Cuda was painted in a solid color without clear.
No matter which type of paint surface is being worked, sand only enough to remove the oxidation and surface flaws, and leave a uniformly de-glossed surface. Don't chase deep imperfections with concentrated sanding in one area, but take a uniform cut over the entire surface. It's difficult to tell if you've gone far enough when the surface is wet (unless you're working in bright sunlight), but wiping the area dry shows the remaining flaws and shiny areas that need more sanding. The paint revival on this 'Cuda began with a cut using 1500-grit paper. Sanding serves as the first step in the buff job and provides an ideal surface for paint adherence. The heavy oxidation is clearly visible, even wet, so it's easy to tell from the distinct color change when the surface is sanded sufficiently.
It's basic, but filler mixes...
It's basic, but filler mixes with hardener, taking a few minutes to cure. To keep the filler clean, never double-dip the stirring stick into the fresh filler, mix on a clean surface, and apply it with a spotlessly clean squeegee with a nice edge.
Touch-ups can range from dabbing in some paint from those little car dealer's bottles to blending-in a repaired panel. In most cases a repair is just that, a fix, and perfection isn't always possible, though certain colors are easier than others. Solids such as the red on this 'Cuda are easier than metalics, and dark metalics can be nearly impossible. The paint should be the same type as that being repaired, preferably the same batch that was used in the first place. Barring using the same paint, take a sample of the original color to the paint jobber and have the paint-match verified at the time of purchase and the tint adjusted if required. Formula tints won't typically be a perfect match. If the paint doesn't match, the repair will stand out.
Achieving a perfect blend into a panel is much tougher than painting a panel section to a character line. Lines or panel gaps break the surface plane to the eye, making it difficult to perceive subtle variations in the paint. With difficult metalics, cutting-in to a line is probably the best way to hide the repair. To paint to a line, back-mask-rather than laying the tape flat to the edge-so it's folded back in the middle at the line, giving it a soft edge.
For very small chips, a paint-brush dab is probably the best quick repair, but not a perfect one. For the best result, try to fill the hole with multiple applications until it's even with the surface. Avoid building up a ridge of paint outside the hole. After filling, the spot can be color sanded and buffed. Larger flaws like surface gouges or large chips can be filled with spot putty. Traditionally, these are quick-drying nitrocellulose (lacquer) products. Spot putty shrinks slightly and cannot be effectively used in thick layers, since drying time goes up exponentially as thickness increases. Catalyzed spot putties are available, but the grain generally is not as fine as the nitrocellulose formulas, and if you have many small repairs, constantly mixing fresh batches slows progress. Fill ever-so-slightly higher than the surface of the chip or gouge. Don't cake the putty on or it will be impossible to sand it level without sanding through the adjacent paint and distorting the paint's surface.
You're not slopping plaster,...
You're not slopping plaster, so apply the filler as smoothly as possible and don't over-work the material.
Once cured, the filler is...
Once cured, the filler is sanded level. We used 80 grit on a short hard board. It can also be filed with a Surform file to rough it, but on a small repair like this it isn't necessary if it's applied nicely.
Next the area is glazed with...
Next the area is glazed with spot putty to fill the sanding scratches and minor surface imperfections. We used the same nitrocellulose spot putty used to fill the chips. The key is an even, thin coat using as few passes as practical. Overwork the spot putty and it will wad up.
Once dry, the spot putty is...
Once dry, the spot putty is wet sanded with 400 grit.
Once the flaw is filled and sanded, it can be touched up with paint. If the spot putty is smooth and sanded dead-level, usually no primer is necessary. Some distortion will be visible, but this will be filled by the paint and sanded-out once it dries. Larger repairs may need some surfacer to help achieve a perfect finish, but the painted area has to be extended over a larger area to cover the primer. Small touch-ups (chips and small gouges) can be done with an airbrush. We use a $5 unit from Harbor Freight Tools which works great. Larger repairs (panel blends) are handled with a touch-up gun. For small repairs, we like to over-reduce (double the normal reduction) the paint and use a slower than normal reducer. With this mix, use multiple light coats to color-up without excessive gluggy buildup. After it's colored-up, reduce it further (up to four times normal reduction) so that it almost sprays tinted solvents to blend-in the repair. Larger repairs use a more conventional mix, but thinned-down for blending, extending the repainted area.
The final buffing should be done only after all the repairs are made. There are countless products on the market for buffing paint. After cutting, machine buffing is required to bring back the gloss. Use the professional bodyshop compounds made for machine polishing. 3M makes an excellent line of compounds for a variety of applications. The buff-out is a two-step process starting with a coarser cutting compound to remove the sanding scratches. Next, a polishing compound, called a finishing glaze, is used. The finishing glaze removes the swirl marks from the compounding step and gives a super high-gloss finish.
Buff with a dedicated buffing machine. Though it looks like a sander, it turns the slower rpm (1500-2000 rpm) necessary to reduce the chances of burning the paint. Paint buffers are rotary, not the orbital machines sold for Saturday wax jobs. Quality buffing pads are a necessity, and are usually made from wool. Two types of pads are required: a coarse cutting pad for the compounding and a fine polishing pad for the final finishing glaze. Foam final finish pads are available, but we prefer wool.
The compound usually has instructions on applying the sauce, but handling the machine correctly takes skill and experience. Avoid using too much pressure and let the compound do the work. The main danger is catching an edge that can burn through the paint in an instant. When buffing, hold the machine at a slight angle, so only one side of the pad works the surface at any given time. Pay attention to the direction the pad is rotating and make sure it always rotates off the edge or body line rather than into it. In areas such as around doors, the hood, or trunk, slightly open the piece to raise the edge so the pad can ski over it without going directly into the edge of the adjacent panel. Where it's not possible to rotate off the edge, orient the buffer so the outside of the pad wipes over in line with the edge.
After a while the pad begins to load up with dried compound and needs to be spurred periodically to keep the surface clear of buildup. Turn it on and run the point of a screwdriver it across the surface of the pad. When switching from the cutting sauce to the polishing formula, thoroughly wash the car to remove the remnants and dust from the cutting compound. Particles are picked up by the polishing pad, introducing them into the fine polishing operation. Buffing slings compound all over, and if it's allowed to dry, it will adhere to the paint. Always clean the jambs, glass, and other areas while it's fresh, using plain soap and water.
A coat of primer-surfacer...
A coat of primer-surfacer is next, followed by a wet sanding with 600 grit. That's the extent of the prep in this area.
The back of this quarter has...
The back of this quarter has plastic filler, and it's cracked. When the car is restored it'll get metal, but for now, we'll patch it up.
Ground, refilled, spot puttied,...
Ground, refilled, spot puttied, and sanded, the next step is primer surfacer and the final sanding.
These small flaws are painted...
These small flaws are painted with an air brush, using many coats of very thin paint.
We had a deep gouge on the...
We had a deep gouge on the driver's door. Because of the size of the flaw, we airbrush some primer over this area for a smoother fill than the spot putty alone can provide. The area needing paint to color the primer spot is now much larger than the original scratch.
A relatively wet mix of paint...
A relatively wet mix of paint is stirred into a touch-up gun, and the repaired area on the door edge is painted. The panel isn't masked, we just use some wide tape around the jambs. Each successive coat gets more reducer, and the painted area is extended.
Repairing paint may have been a stop-gap measure in our case, but the resulting glass-like finish is worth it. The car has a totally renewed look. Since the paint was so flawed to begin with, the repairs took three days to complete. It isn't a Saturday afternoon's work, but it's a lot quicker than a respray. The larger panel blends with our solid color are no less than perfect, with not even a haze of an edge visible where it meets the old paint. This was partly because we still had a half-quart of the paint used the last time the car was shot. It had been on the shelf for ten years, but still worked fine and matched perfectly. Some of the smaller repairs weren't quite invisible, but much less apparent than the original flaw, while others blended perfectly. Going down the road, the 'Cuda looks red-hot.
On the repaired quarter-panel,...
On the repaired quarter-panel, the paint is blended into the adjacent panel using the same technique as on the door.
Once all of the paint repairs...
Once all of the paint repairs are completed, the spots are wet sanded with 1500-grit paper until evenly flat. The whole car is then given a quick, light sanding with the 1500 grit to eliminate any overspray and in preparation for the final buffing.
Apply the cutting compound,...
Apply the cutting compound, which removes the sanding scratches and brings a dull shine to the surface.
Once the first cut is completed,...
Once the first cut is completed, the car is thoroughly washed. The cutting pad is swapped for a polishing pad, and the job is gone over with the finishing glaze to remove the swirl marks and bring up the final gloss. Man, does it look good.
Here's the repaired area of...
Here's the repaired area of the door. Even up close, not a hint of a blend line. The deep gouge shown earlier is in here somewhere, but we couldn't find the spot to take a photo. Likewise, the blend at the quarter repair is perfect, the fixed chips on the trunk extension panel are basically gone, and the highly oxidized hood and fender tops gleam like fresh paint.