This Makes All The Prior Work WorthwhileOnce the car is stripped, the bodywork done, the primer applied and blocked to perfection, it's time to lay down the final hue. The color coats are the pay-off, where all that work and effort are rewarded with a finish worthy of a Corvette. Really, once the proper foundation is laid with diligent work to this point, applying the final color coats is just like adding icing to the cake. The process of building our project C3 is ongoing and real, and as it is, the main body tub still isn't quite ready for the final finish coats. However, our paint plan has always been to spray the removable panels individually and off the car, allowing full coverage of the edges and jambs without seams. This is a common technique in painting top-level show cars, but taking this approach comes with its own set of caveats. Foremost on that list is ending up with a perfect color match from panel to panel. There are two main factors here: the paint and the application.
We are painting the removable...
We are painting the removable panels separately from the main body, which means they must be racked in the booth for spraying. We did not want overspray on the back side of the hood, but needed the paint coverage to include the edges, so the panels were masked appropriately.
At no stage is cleanliness...
At no stage is cleanliness more important than when in the booth for the final spray-down. Cleaning begins with a dust-down with compressed air, and then a solvent clean with a wax and grease removal solvent. We used Sherwin-Williams R7K158 Ultra Clean here.
An automotive refinishing...
An automotive refinishing tack-rag has a sticky coating that is designed to pick up dust without leaving a residue on the surface. The final wipe is just before the spraying starts.
Obviously, for the panels to match, the paint must be a perfect match. If more than one batch of mixed color is involved, it always pays to "bulk" the paint together, and then pour it back into the cans after thoroughly mixing the batches together. With this move, it all becomes one batch of the same mix. The second factor-the application-is a little more nebulous, and here there are a few variables including the paint itself. If the color coats include effects, such as pearls, candies, or heavy metallics, getting a consistent look becomes more difficult, and depending upon the effect, can be impossible. Even regular metallics can be difficult, but there are techniques to negate the potential for mismatches, such as using consistent numbers of coats and finishing with a fogged mist-coat technique.
For our Corvette project, we are using Planet Color's Chumma Orange, which is a solid orange. A solid lends itself very well to painting the panels individually, with little chance of a mismatch, as long as the coverage is complete and sufficient to hide the primer. Our painting strategy is to paint the hood, doors, headlamp assemblies, roof panels, and miscellaneous small parts first, and then paint the main body. This approach will yield complete paint coverage of the edges, hood gutters, and jambs. The result once the car is assembled is a seamless look that is much more detailed than the factory finish.
Shooting Color: A Three Step Process
The final spray session actually begins with a preliminary step-the sealer coat-which technically is an extra primer coat. The sealer coat helps fill and smooth minute sanding scratches, and it imparts a consistent bed for the basecoat, which helps color uniformity. Primer sealers are designed to go on smoothly and require no sanding prior to the topcoat application. In auto refinish terminology, the topcoat is applied "wet-on-wet" over the sealer, meaning the paint is applied just after the solvents are allowed to flash from the applied sealer coat, in a matter of minutes.
The first stage isn't a finish...
The first stage isn't a finish stage at all, but rather the sealer coat, which provides an improved surface for the color coats to come. We like the base tint to resemble the final color.
The basecoat is where the...
The basecoat is where the real color comes on, though the finish is dull. With every step of the final spray process, the idea is to apply the material as smoothly as possible.
Once given sufficient time...
Once given sufficient time to flash and dry to the touch, the basecoat can be given a light dusting with a tack-rag to remove any dry overspray that settled on the surface.
One thing we like to do at the sealer stage is mix a sealer that is reasonably close to the color of the topcoat, orange in the case of our Corvette. Sherwin-Williams' sealer system comes in a full range of colors, and we used the available red and yellow to mix an orange primer. The advantage is the tinted sealer will allow the base color coat to "color-up" or hide the primer much more easily and consistently than would be the case with a contrasting base. Fewer coats of base will reduce the tendency for undesirable texture to develop while the color is applied. Another plus with a tinted primer is that minor stone chips that may come from driving the car are much less conspicuous if there is orange under the paint instead of a contrasting color.
For the final finish, we are using a basecoat/clearcoat system on this car, which is the most popular system in auto refinishing these days. This includes the basecoat, which gives the finish all its color properties, but none of the shine and durability of the completed paintwork. Once the sealer has been allowed to flash, the basecoat is the next step, but only after a careful inspection of the sealer coat. There is no room for flaws at this stage of the game, and if the sealer coat is rough from improper solvent selection, air pressure, contamination, or poor application technique, there is no use in continuing with the basecoat. Small dust nibs or other flaws need to be corrected without compromise.
The basecoat applies like the lacquer paints of old, going on with some solvent gloss, and then dulling and drying quite rapidly as the solvents flash out. The goal is to apply just enough basecoat for uniform color coverage, and no more. Two complete coats are adequate in most cases. Properly applied, the base should be smooth and consistently level, with imperceptible surface texture. As with the sealer coat, if the base does not meet these standards, there is no use in continuing with the clear before correcting the situation. You won't meet the goal of show-quality paint if the base does not lie down perfectly.
After the base is allowed to flash and set, it's time for the money coat-the clearcoat application. Here we need to apply enough material to allow the clear to be sanded and polished later without breaking through to the basecoat or leaving the remaining clear too thin. Three coats are generally plenty of clear for cutting and polishing, but with every coat there is potential for more texture or orange peel to build. It is not practical to cut and buff every inch of the paintwork of a car, so the quality of the finish off the gun is important. While the exterior panels will invariably be color-sanded and buffed, areas such as the gutters, hinge box, and jambs will forever tell a tale of how nicely the finish came down. Frankly, if the texture in the clear is really excessive, even cutting and polishing will never remove all traces of the roughness. The painter must strive to get the clear to flow to as glass-like a finish as possible with the clearcoat. Variables here include the solvent mix, the equipment, air pressure, and technique.
Clearcoat is what gives the...
Clearcoat is what gives the final brilliance in a basecoat/clearcoat paint job. Again the goal is to lay the clear down with as little texture as possible, striving for that perfect flow-out.
The finished hood gives us...
The finished hood gives us plenty of inspiration to complete our painting project. the planet color materials delivered fantastic results, even before buffing.
Perfect coverage of the edges...
Perfect coverage of the edges is one of the advantages of shooting the panels off the car. These edges will never get buffed, but the finish quality is up to the most discriminating standards.
We were quite happy with the way the Planet Color base and Ultra 7000 clearcoat laid down on our L88 hood. The final look is nothing short of magnificent, and will only get better when given a final cut and polish. Shooting the loose panels first gave us an opportunity to identify any potential problems in a more confined situation than if we had begun with the main body first. With the results of the paint here, it looks like we are well on the way to the type of outstanding paint we think our Corvette deserves. Paint is one of the most time-consuming projects that an enthusiast will get into on a vehicle, and also one of the most rewarding. Here we demonstrated the techniques, and our project car's paint will be completed and polished in a future issue to show the final result.
|DIFFICULTY INDEX ::: III |
|ANYONE’S PROJECT | no tools required ||I |
|BEGINNER | basic tools ||II |
|EXPERIENCED | special tools ||III |
|ACCOMPLISHED | special tools and outside help ||IIII |
|PROFESSIONALS ONLY | send this work out ||IIIII |