Body Preparation and Painting
From The Scratch-Built Hot Rod
Chapter 14: Body Preparation and Painting
There are many authoritative and well-written books already on the market covering the subject of automotive finishing, as well as custom painting. In addition, there are some very fine websites with great instructions for anyone hoping to paint their own vehicle. Novice painters should consult as many of these sources as possible to learn how to do basic body work, how to prepare metal surfaces properly and how to apply primers and paints.
Since your author is only a novice painter himself (this being his first base coat/clear coat paint job) this chapter will contain very little in the way of detailed "instructional" material. It is not intended as a painting or body work tutorial.
Instead, this chapter will provide a photojournal of the preparation and painting experience, as seen through the eyes of a beginner. Along the way, a few tips, tricks and shadetree tools will be offered up, but they are intended only to show how this one novice struggled through the painting process.
As any professional painter will quickly tell you, a quality paint job is 95 percent preparation. What goes on prior to applying the color is far more important than spraying the paint itself. All told, what you are about to see required over 1600 hours to complete. However, less than 1 percent of that time was spent spraying color or clear.
While a skilled and experienced paint and body technician can achieve much more in far less time, the amateur backyard painter must somehow compensate for his or her personal lack of skill and experience. That compensation almost always comes through a heavy investment in time and effort.
These are the basic rules that were followed during the preparation and painting of this project:
- Avoid short cuts.
- Read product labels and abide by the manufacturers' recommendations.
- Go the extra mile.
- Don't rush the process.
- Keep at it even when progress seems painfully slow.
- Guide coats are your friend. Use them.
Blow everything up
The very first step to putting color on your car is to blow the whole thing up. Well, almost. What you need to do is tear apart everything you have just built up. It can be very disheartening to see your "almost completed" hot rod stripped down and totally disassembled, but this is an essential on the road to a nice paint job. The car must be dismantled so that every part and every piece can be properly prepared and painted.
Bust the rust
|Nearly every part of a scratch-built car that comes from a donor vehicle is going to be covered with years of rust and corrosion. Media blasting equipment is essential for getting your parts cleaned up for painting or powder coating (or chroming, for those with a large checkbook).
For this project, two different blasters were used. A stationary cabinet blaster is the tool of choice, because it is cleaner and more efficient to use. For parts that were too large to fit in the cabinet, a portable "pressure pot" blaster was used. The majority of the blasting was done using glass bead as the blasting media.
Large parts, like the rear end and front axles, were done outdoors on large tarps. The tarps allow the user to collect a decent percentage of the media and to use it again. Photo 14-1 shows the results of using the portable blaster. It is quite obvious which axle has been blasted. Photo 14-2 shows the rear end after being blasted.Literally hundreds of parts, from bolt heads to oil pans, were blasted for this project. It is a time-consuming and rather mundane task, but well worth the effort.
|An entry-level Eastwood powder coating gun and a used $50 electric oven were used to powder coat the chassis parts on the project. Anything that could fit in the oven and withstand the 450 degree temperatures required for the coating process became a candidate for coating. Photos 14-3 and 14-4 show just some of the many pieces that were powder coated. Items that could not be powder coated were painted with spray can aluminum (metallic) paint. These parts will have to be repainted from time to time to retain their finish and to protect the metal.|
|The headers and side exhaust were painted with 1200 degree aluminum paint (Photo 14-5).|
Frame prep and painting
The first step to prepare the frame for painting is to grind and sand smooth every weld holding the frame together, as well as every weld on every bracket that is attached to the frame. This is done with a combination of burrs, grinding wheels and sanding wheels. This is a long, tedious and boring process that takes many days to do right. In addition, the entire frame is sanded or wire-brushed and then wiped down numerous times with wax and grease remover to get rid of any possible surface rust or coatings applied by the manufacturer. This process also cleans off the cheap spray can primer that was used throughout the fabrication process to prevent rusting of the newly-welded areas.
The frame was then shot with a coat of Dupont Nason epoxy using a Harbor Freight purple gun. After letting the epoxy coat dry two hours, as recommended, three coats of Kustom Shop Polyester High Build Primer were applied. The frame was suspended on chains and hooks while it was being painted, so that it could be rotated for painting on all sides (Photo 14-6 and 14-7).
After drying overnight, the frame was set down flat on supports, and the long and tedious task of feather filling and sanding all the welds and joints was begun. This step is necessary to eliminate any grinding or sanding scratches left after smoothing the welds (Photo 14-8).
|The next step is to block sand each of the four surfaces of the rectangular frame rails all the way around the chassis. Although it is not readily apparent to the naked eye, rectangular tubing is not flat on every side. In fact, every side of the tubing is slightly concave. I suspect this is due to the pressure exerted by the rollers that are used to shape and form the tubing. Whatever the cause, if you want your frame rails to be absolutely straight and flat, each surface, top, bottom and both sides, must be skim coated with filler and then block sanded level. When the block sanding is completed, the entire frame was shot once again with a coat of epoxy. This is to assure that any "sand throughs" are covered. Then, two more coats of urethane primer are applied and the entire frame is block sanded with 400 grit paper (Photo 14-9 and 14-10).|
|After a complete wipe down with wax and grease remover, and a once over with a tack cloth, the Restoration Shop Firethorn Red Pearl base coat is applied using a Devilbiss Finish Line 3 gun equipped with a 1.3 mm tip (Photos 14-11 and 14-12).|
|After waiting the recommended dry time and wiping down the frame with a tack cloth, three coats of Kustom Shop clear were applied (Photos 14-13 and 14-14).|
|The clear was later color sanded (wet) by first cutting down the orange peel with 800 grit paper and then smoothing everything out with 1500 grit. The clear was then buffed with Meguiar's "Speed-Cut" #95 (Photos 14-15 through 14-18).|
The finished rolling chassis
At long last, the fully painted rolling chassis can be reassembled. Here is a gallery of the finished product from various angles and viewpoints (Photo 14-19 through 14-27).
|At the end of our chapter on body fabrication, we left off with the sheet metal panels simply tack welded to the skeleton. To proceed, all of those seams and edges must now be welded up tight and all the beads ground smooth. No earth-shattering techniques are involved here, just lots of time and hard work. Photos 14-28 and 14-29 show the "weld-n-grind" in progress.|
Once all the welds are stitched up and ground smooth, they will still be quite rough and uneven. Evercoat "Everglass" is applied to every weld seam on the car (Photo 14-30). This is a body filler that contains short strands of fiberglass material mixed in with the resin and putty. The short-strand filler will help reduce the potential for hairline cracks developing at the welded seams in the future.
Once the Everglass has cured, it is sanded with 80 grit (or coarser) paper to remove the major rough spots and create a fairly level working surface. Then, Evercoat Rage Gold is applied to smooth the body panels and welded areas, and to begin the initial straightening of all the body panels (Photo 14-31 and 14-32).
One of the most frequently asked questions by those seeing this car and discovering it was scratch-built is, "How did you make the belt line and accent lines?" It is no wonder they ask this question; accent lines would normally require high-end tooling and pressure bending, or a massive amount of hammering over a wooden buck.
Since the builder had no access to those tools and did not possess the necessary metalworking skills to shape the metal by hand, a much different approach was taken to create accent lines: garden hose. Or, to be more precise: sprinkler hose. You can find this hose at any hardware store or garden center (Photo 14-33). It's flat, rather than rounded, giving it a natural shape very close to the shape of a traditional accent line.
To begin, the accent lines are drawn on the body wherever they are desired. In this case, a basic belt line, and then a line that will define the rear window panel typical of the sedan/delivery body style (Photo 14-34). The lines are drawn to the exact width of the hose, and then masking tape is laid on each side of the line. The tape prevents the adhesive from getting into the body filler anywhere except under the hose (Photo 14-35).
The hose sections are cut to length (one for the cowl, one for the door, and one to run from the back of the door to the rear hatch) and ground down on each end to create about a 45-degree angle. This allows the accent lines to better blend into the body panels wherever they start and stop (Photo 14-36).
The adhesive is common contact cement available at any hardware store. DAP Weldwood was used here. It is brushed onto the masked area and to the back side of the hose sections, and allowed to dry as directed (Photo 14-37). Each section is then carefully aligned and firmly pressed in place (14-38). Once contact cement "grabs", it grabs. And, under normal circumstances, the glued parts cannot be maneuvered around or repositioned. So, make sure it is exactly where you want it before you allow the two surfaces to come in contact.
Photo 14-39 shows the complete belt line glued in place.
The line that will define the window panel requires a bit of additional work, due to the two curved corners (Photo 14-40). To form the hose to fit these curves, it must be sliced around the inside radius of the curve (Photo 14-41). These slices were made using a cutting blade on a 4 1/2" grinder, while the hose was held in a vice. After the initial cuts are completed, a second pass is made with the cutting wheel, to remove additional material at the tips of each cut, creating something of a pie shape. You'll know you've removed enough material when the hose can easily be bent to conform with the line of the curve, without any kinking or bulging.
|The window accent line is glued to the body in the same manner as the belt line (Photo 14-42). Photo 14-43 shows all of the accent lines glued in place. Evercoat short-strand fiberglass filler is applied to fill all the gaps at the top and bottom edges of the hose pieces, to fill the cut ends of the hose, to fill in where the triangular corner pieces were added, and to fill in the multiple cuts made to form the top curves of the panel accent. This is done primarily to reduce the potential for air bubbles and voids forming when fiberglass cloth is applied in the next step.|
After sanding down the Evercoat filler, the accent lines are covered with two layers of resin-soaked fiberglass cloth, and allowed to cure (Photo 14-44). The fiberglass cloth should extend about 2" beyond each edge of the accent line. Although it can not be seen clearly in this photo, triangular sections of hose were cut, shaped and fitted into each lower corner (arrows) of the window panel prior to applying the fiberglass cloth. Once glued in place, these sections were further shaped and rounded using a small drum sander mounted on a Dremel tool. The corner pieces are intended to provide a nice curved transition from the belt line to the window accent line.
The cured fiberglass is sanded down to remove the major bumps and imperfections, and then body filler is applied and sanded smooth (Photo 14-45). Photo 14-46 provides another view of the finished accent lines.
Filling and block sanding are boring to do, and even more boring to photograph. Instead, what this section will concentrate on are a few tools and tips this novice discovered along the way. While the pros will have much better ways to accomplish these ends, these are just a few solutions that worked while preparing this car for paint.
|Because of the way this body is fabricated, the "straightening" process is more demanding than a typical car with factory-made panels. One of the most challenging areas of the car is the back end of the body, with its big sweeping curve, its compound-complex corners, and the tricky "corner-cap" at the very top of the curve. To get these curves straight it is not only essential to block sand them well, but also to apply the body filler effectively. This requires flexible applicators that are much longer than those normally found at the auto parts store. Two long applicators were particularly helpful. The first was cut from 3/16" Plexiglas (Photo 14-47), and is shown being used in Photo 14-48.|
|The other very effective applicator was no more than a section of galvanized roof flashing (Photo 14-49), which did a particularly good job on tighter corners and the sweeping rear corner curve (Photo 14-50).|
Long block sanding tools are also critical for effective block sanding. This one (Photo 14-51) is a Plexiglas strip with discarded 35mm film canisters epoxied to the back side as hand-holds. Adhesive-backed sandpaper is mounted on the "block" (Photo 14-52) and the block can then be formed around the curved panel to produce a uniform and level surface (Photo 14-53).
Although not homemade, another very effective sanding tool for curves is this one from Dura-Block (Photo 14-54). The paper is wrapped loosely around the block (Photo 14-55), so that it can be formed to fit the curve being sanded without creasing the paper (Photo 14-56).
|Other more typical sanders were used at various points during the straightening process, including an air-driven "long board", rotary sander and orbital sander. Also, an air-driven "jitterbug" was used. However, the control paddle which sets the jitterbug's speed can be very difficult to regulate, and if over-revved, the machine can do major damage to the sanding surface. To solve this problem, the jitterbug can be upgraded with this "governor". The governor is nothing more than a bolt through the paddle, with a couple of locking nuts that limit the top speed when the paddle is depressed (Photo 14-57 and 14-58).|
Photos 14-59 through 14-61 are progress shots taken during the straightening process and body filler work.
|As mentioned when the body was being fabricated, the car was originally designed and built with an opening rear hatch. However, with the addition of a pickup bed at the rear of the car, it was difficult to operate this hatch, and even more difficult to reach into the car to store any cargo behind the seats. Also, the large rear window in the hatch did not seem to fit the overall design of the car. As a result, the window was downsized and made more rectangular (Photo 14-62). In addition, the hatch was permanently set in position and welded in place so that it no longer opens (Photo 14-63).|
As the fill-and-sand straightening process progresses, we need to achieve greater and greater precision in straightening the panels. To do this, three coats of Evercoat Slick Sand are sprayed on the body using a Devilbiss Finish Line 3 gun with a 2.2 mm tip installed (Photo 14-64, 14-65, and 14-66). This fill primer is block sanded using 3M's dry guide coat to find any high and low areas still remaining. After trying both inexpensive spray paint and 3M's product as the guide coat, the 3M product seemed far easier to use, and more effective to boot. It may be a bit more expensive than buying spray cans, but the dry guide coat seemed to be a far more useful product.
If there are areas too low to be sanded out, they are either skim coated with body "icing", or shot with more primer to build up the area. It is then a back-and-forth process of block sanding-primering-block sanding until the dry guide coat no longer reveals any low spots or high spots, and the body panels are perfectly straight.
There are differing opinions on when the epoxy primer should be applied. Some painting experts say it is best to lay down the epoxy at the very beginning, directly over the bare metal. Others say it is best to wait until the body straightening work is complete so that there are no "bald spots" where the epoxy is sanded through to bare metal. And a third group says it is fine to do it either way...just so long as a coat of epoxy is applied.
For this project, the epoxy coat is being applied near the tail end of the body straightening process. Photos 14-67 to 14-69 were taken just after application of the Dupont epoxy coat.
As a final step before shooting color, two more coats of urethane primer are shot over the epoxy, and are very carefully block sanded (wet) with 600 grit paper using 3M dry guide coat. Whatever imperfections remain in the primer after this final block sanding will be magnified about 100% when the color and clear are shot over the top.
Photos 14-70 to 14-75 provide various views and close-ups showing this final primer coat during block sanding. It is finally ready for some color.
Base coat clear coat
Remote pot paint gun
Before we begin, here's a tool worth mentioning. It was actually fabricated and used for shooting the very first coat of primer on the car but deserves mentioning here because it is really critical for shooting the base and clear.
On almost any hot rod, there will be locations that are very difficult to paint, particularly if your siphon or HVLP gun is not equipped to shoot upside-down or in tight quarters. You can get away with shooting primer at odd angles because the overspray and orange peel can easily be sanded away. But when shooting base and/or clear, you want the paint to lay down as smooth as possible right out of the gun, which usually means shooting at a right angle to the painting surface.
|The solution used for this project was to modify an old siphon-type detail gun and turn it into a "remote pot" gun. Arrow "A" in Photo 14-76 shows where the siphon cup originally attached to the gun at arrow "B". The hose is approximately 5' long, and came from an old portable air pump. The important part is that the hose had threaded fittings on each end, which happened to button up perfectly with our old gun parts. Photo 14-77 shows the changes made on the gun. A 1" long threaded pipe fitting ("A") is used to attach the hose to the gun. The fitting on the gun had limited threads and a somewhat specialized end, so an O-ring was inserted to ensure a tight fit where the black pipe fitting meets the gun. To conserve space and cut down the length of the gun, a street elbow ("B") is used for attaching the air hose.|
|Photo 14-78 shows the "remote cup", which required no modifications. The threaded fitting on the hose was just the right size to attach directly to the cup. After just one test run, it was quickly apparent that the remote pot, even when full of paint, was very light and unstable. Any movement of the gun and hose would cause it to tip over. So this very high tech "Polyethylene Paint Cup Stabilizer" (a plastic coffee can filled with sand and a peanut butter jar stuffed into the center) was invented (Photo 14-79).|
|To clean things up a bit, a hole was cut in the can lid and snapped back in place. It's not billet...but it serves its purpose (Photo 14-80). Photo 14-81 demonstrates how handy this remote pot sprayer can be. The area under the visor was simply unreachable with my HVLP gun. The remote gun worked like a charm for primer, base and clear coat.|
Paint booths should accomplish two major goals. First, they should keep the painting area isolated from dust, dirt or airborne debris. Second, they should provide a means of ventilating the painting area and removing the cloud of overspray that inevitably results when using a spray gun. You don't want dried or drying paint mist landing on the paint surface as it flows out; a good paint booth forces as much of that mist as possible out of the immediate area.
Paint booths can range from six-figure professional setups to $10 booths constructed of Visqueen and box fans.
The "booth" used for this project was created with standard plastic tarps found at hardware stores and farm centers. These tarps have holes and grommets every three feet, which makes hanging them an easy task. To make this booth reusable, 1x2 wood cleats were fastened to the ceiling around the perimeter of the 24x28 shop. Small hooks were screwed into the cleats to match the spacing of tarp holes, so that the tarps can be easily hung or taken down.
The tarps were cut to make openings around the two windows in the shop. One window serves as the intake, and the other serves as the exhaust. A box fan is placed in each window, one pulling air in and the other pushing air out. In addition, an overhead JET air cleaner is run at full speed during the painting process to help remove the paint mist.
To get acclimated to the base coat/clear coat spraying routine, and to ensure the gun is set up properly to achieve a nice finish, the car's "parts and pieces" are painted first (Photo 14-82). Then the hard-to-get-at detailed areas of the car are painted (Photo 14-83 to 14-86).
The BIG shoot
The base coat and clear coat were both shot with a Devilbiss Finish Line 3 paint gun using a 1.3 tip. The color is Restoration Shop Firethorn Pearl Red and the clear is Kustom Shop (all products available online from TCP Global).
Three coats of base were shot, tacking down between each coat to remove any paint "dust" that may have settled on the car. Then, three coats of clear were shot over the top.
The results of this first-time effort at shooting base coat/clear coat are shown in Photos 14-87 to 14-92, which were taken immediately after the painting session.
After waiting the recommended time period for the clear to dry, the pieces of the car were individually color sanded and buffed. They were then reassembled and a final buffing was completed with the car intact.
The results are shown in Photos 14-93 to 14-100.
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