Monday, March 10, 2008

How to Paint Your Car at Home

Heres an Artical from Carcraft Maginzine on how to paint your car at home.

How to Paint Your Car at Home

How to Paint at Home
photographer: Steve Dulcich
BEFORE
AFTER
1. After thoroughly cleaning the car with detergents followed by a wipe-down with wax and grease remover, the work starts by sanding down the old paint with a dual-action (DA) orbital air sander. The DA sands without digging in like a rotary sander or grinder. Sanding the car down to at least the level of its original paint offers a great surface to build on if it’s in good shape. Heavy duct tape protects the windshield molding from getting scuffed by the sander.
2. On the lower driver-side quarter we struck a solid sheet of body filler over wire mesh, hiding some serious rust. A tape line was laid out, and the offending area was cut loose with a cut-off wheel. The inner trunk floor extension was also rusted, so most of that got the knife too.
3. This is the quarter after the final cut. Make sure when making repairs that the work area is pruned back to solid metal.
4. We culled a replacement section for the quarter-panel from a wrecked Dart Sport and painstakingly trimmed it for an exact fit so we could butt-weld it in. We cut the piece from the donor car with the inner panel still attached, and welded it in that way, so that the factory join between the two panels remained at the bottom, front, and rear. These butt-welding clamps are from The Eastwood Company, and keep the panel edges lined up.
5. The new panel was MIG-welded in place. With its confined heat zone, MIG welding keeps distortion to a minimum. MIG gear is affordable enough now to be within reach of the hobbyist, with this Campbell Hausfeld unit from Harbor Freight Tools priced under $400. Make sure to step up to a gas-bottle system rather than the gasless flux core wire, since the latter will leave flux in and on the weld. The auto-darkening helmet, also from Harbor Freight, is a significant step to welding ease and worth every penny.
6. After grinding the weld and some hammer-and-dolly work, the result was a solid, seamless repair. This area will get just a very thin coat of plastic filler to get the surface perfect.
7. The car had several other smaller rust areas, some of which exhibited only minor pinholing through the surface. These pinholed areas will blow out paint or filler in a short time, so don’t be tempted to just cover them up with body filler. Here, the rusted corner of the quarter ahead of the rear wheel was cut out and replaced with a patch. To prevent future corrosion, thoroughly clean the rust area while it’s accessible, and coat the backside of the repair sections with weld-thru primer.
8. A cut-off wheel is useful for grinding back any excess welding buildup at the tacks. The thin cutting wheel can be focussed precisely on the weld beads to avoid unnecessary thinning of the sheetmetal. Final dressing of the repair is done with an angle grinder using a 40-grit grinding disc backed with a rubber pad.
9. Follow the mixing instructions to prepare the plastic body filler. Apply a light skim coat to the patched area and the repair is done.
10. Minor surface flaws are easily fixed with a skim of filler. Apply the filler smoothly with a plastic spreader.
11. After it dries, the filler can be filed with a Surform blade (a ridged, half-round shape is the best one to get). Unless a huge amount of shaving and shaping is needed (it shouldn’t be), forget the old “consistency of cheese” advice about when to file it back, since that’ll only lead to peeling off or overfiling the filler. Let the filler dry fairly hard, and then rough-shape it with the file until the surface reveals uniform file marks and is properly contoured.
12. The best tool for shaping filler is a long sanding board. For heavy leveling, use 36-grit sandpaper, followed by 80-grit. Try to leave uniform sanding marks and a smooth edge that feathers into adjacent areas. Finish up by DA sanding with 120- to 150-grit sandpaper to smooth the surface.
13. Regular filler has a fairly coarse texture, and is subject to leaving pinhole-size bubbles. The final step of the filling process is to use acrylic glazing compound to fill minor surface flaws and create a superfine feathered edge. Use acrylic glaze sparingly because it takes a long time to dry and can shrink if glopped on.
14. Glazing compounds are designed to sand easily due to their fine texture. A hard autobody sanding board is the best tool to use. They come in either 1/3- or 1/4-sheet sizes. Sand to create a uniform surface with a finely feathered edge.
15. Once the bodywork is done, the car is cleaned again and masked. Since the jambs, engine bay, and trunk of this Duster still had nice original paint, we also masked these areas to protect them from overspray. 3M soft-edged foam tape, which works like weatherstrip, is useful for sealing panel gaps.
16. Masking is an important step in getting a quality job. We bought a 1,000-foot roll of 3-foot-wide masking paper and enough autobody masking tape to do the job right. We left the windshield moldings in place, and tucked the tape under the edges with a thin plastic card. The underchassis is also vulnerable to overspray, and the only way to avoid a mess below is to build a curtain all the way around the underside of the car, taping it to the backside of various panels. A good masking job takes six to eight hours, and will need to be redone before the final paint is applied.
17. Before spraying any material, we did a final wipe-down of the surface to remove contaminants. In some parts of the country, solvent-based products can be used for this step. They work quicker, so check your local regulations.
18. For the first primer coat, we used Valspar epoxy primer. We could have used other types of primer, but for the Duster’s multisurfaced base, epoxy provided the best sealing and stability. Valspar’s epoxy primer combines excellent filling characteristics with minimal shrinkage, but it is slightly harder to sand than traditional high-buildup primer surfacers.
19. A vital step in achieving a top-quality finish is to apply a thin haze of a contrasting color over the primer to serve as a guidecoat while sanding. The guidecoat reveals high and low spots in the body much more effectively than sight or feel alone. We mixed a bit of black basecoat into the primer with double the normal reduction to get the right consistency and color. There’s no need to paint it on; just mist the guidecoat over the surface to get a uniform speckled look.
20. Sanding the primer is critical to a distortion-free finish. Use long, hard boards rather than flexible rubber blocks, which follow distortions in the panels, and whack the surface hard with wet 220-grit paper or dry 150-grit. Coarse paper quickly whittles down the high spots without riding into the low areas. Where trouble areas appear, work the panel as far as the primer’s material thickness will allow, but stop sanding if it cuts through to the layer below.
21. This corner of the hood displays the typical minor distortions that separate “super straight” from “almost there.” After an initial blocking, the remaining guidecoat (near finger) between the cut-throughs on either side reveals a low spot. A short, flexible rubber block or fine-grit paper would have simply blended this area in by floating with the distortion, rather than revealing the flaw.
22. To fix it, we filled the area with a paper-thin layer of glazing compound and feathered it in by sanding with 220-grit sandpaper on a hardboard.
23. Unless the surface is still rough enough after the initial blocking pass to warrant a second primer/filler application, this is the last chance to fix flaws. This distortion in the cowl was also fixed with acrylic glaze.
24. Once the final detail repairs were complete, we sprayed on a second coat of primer/sealer. This blended and filled the detail repairs as well as the 220-grit surface left in the epoxy primer coat by the blocking process. The second primer layer will be sanded to a much finer 600-grit surface for the basecoat and clearcoat. We used Valspar’s Supa Seal polyurethane primer/sealer. After it cures, the epoxy leaves a much more stable surface than softer primer surfacers. We tinted it with some basecoat color to turn it from light gray to a reddish pink to improve coverage of the basecoat stage.
25. When applying the primer/sealer, it’s important to build up enough material thickness so the surface can be blocked back smooth and level without breaking through to the layer below. We applied two coats.
26. We applied a second tinted guidecoat over the primer/sealer and blocked the car out as we did in the epoxy primer stage, this time using finer wet 400-grit paper. All of the flaws exposed by the guidecoat sanded out without cutting through the epoxy primer layer. This is how you know a car is straight.
27. Before topcoating, the car was demasked and washed thoroughly to remove the accumulated wet-sanding slurry from the panel gaps and surfaces. All the edges were wet-sanded, and the entire surface was given a quick going over with 600-grit paper on a soft rubber hand pad.
28. After remasking the car, the surface must be immaculately clean before any color is applied. The Duster was dusted thoroughly twice with plenty of clean tack rags, and then once again just before shooting the basecoat.
29. Valspar’s two-stage paint system starts with the basecoat. It flashes off fast, and dries to a matte finish. When spraying, put down as little base as required to provide uniform coloration. Keep the gun perpendicular to the area being shot, holding it 10-12 inches away. Overlap the strokes 50 percent and move the gun at an even speed. Use the same technique to apply the clearcoat. We used Valspar’s acrylic polyurethane. Depending upon the regulation in your area, shoot the highest VOC mix that environmental regulations allow to achieve the best flowout and finish. The higher-VOC mixes, legal in many areas, use urethane reducer rather than diluent (required in Southern California) in the brew. That’s it for now. The paint needs to cure for at least a few days before it is ready for the final color-sanding and buffing process, which we’ll detail next month when we wrap up the project.

Having a car with nice paint is both the biggest reward and the biggest hassle in car crafting. Between searching for a paint shop that will do a complete repaint on an older car, getting the job done to your satisfaction in a timely fashion, and paying for it, having a car painted can be a harrowing experience. But there’s no reason to let all that stand between your car and a great paint job. After all, you know the old saying: If you want something done right, you’ve got to do it yourself. And you really can if you’ve got the time and patience to do it right.

The most daunting challenge for the first-time painter is understanding the various steps of the process: prep, primer, blocking, and the final spray job and detailing. Taken as a whole, it seems like an insurmountable hurdle, but each step by itself takes no more than a couple of days. Pacing yourself, you can get the job done in a reasonable amount of time if you have a plan and stick to it. We painted this ’70 Duster in just about a month from the time the bodywork was started until it was color-sanded and ready to drive out of the garage.

It may be the oldest cliché in the trade, but there’s no escaping the truth that the final result of any paint job is only as good as the prep work. The Duster was hiding its fair share of damage, with some rust down low in the quarters, and plastic body filler higher up from previous repairs. From the doors forward, the paint was mostly original, but numerous past repairs had left the rear of the car a patchwork of partial repaints. Some were skillfully done, while other were amateurishly overloaded with filler. We took the time to get the bodywork right before moving on.

Another point we can’t hammer home hard enough is that you really need to check your local environmental regulations regarding mixing and spraying paints at home. The local fire department or autobody supply store is probably the best place to start. But even if you stop short of actually spraying the paint yourself, the techniques shown here will at least allow you to get the car ready for a pro to lay down the paint, saving you a ton of money. We’ve assumed you already know how to strip a car of all its trim, bumpers, mirrors, grille, and other items that need to be removed before you paint it, so let’s get down to the nitty-gritty details.
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