How to Properly Sand, Prime and Pick the Right Paint for Your Car

When Editor Kinnan laid out the plan for this paint series, he headedthis installment with these words: "There are too many options! How doyou choose primer, sealer, paint, clear, and so on?"

So we started digging--visiting the various paint companies' Web sites,talking to painters we knew, reading material tech and safety sheets,boning up on our chemistry . . . until at one point, we saw the light.There's a really easy answer to this question: Start with the color youwant. All the rest will follow.

After Kinnan's '69 Camaro was soda-blasted back in Part 2 of our series["How To Strip Paint"], it was rolled down to Santos Truck &Auto Repair where Arturo prepped the car for its primer coat. The firstorder of business was to blow off any remaining soda then scuff thefresh sheetmetal with 320-grit paper on a d/a. Those rust spots insidethe driprail will get a little attention with a grinder.

Too simple? Not when you look at it this way: Automotive refinishing isthe kind of subject about which five painters will give you 15 differentanswers to the same question. But there was 100 percent agreement amongall our sources on one key element: Stick with one company's paintsystem. Do not mix materials from different paint companies or you riskbonding, adhesion, and durability problems. If that custom-mixed paintjob starts to crack, fade, or flake off your car, none of the paintcompanies will stand behind their guarantees because they can blame theproblem on compatibility issues with the other guy's paint chemistry.

So the easy way to select your paint materials is to go through variouscompanies' paint-chip books, find the color you want for your car, thenuse that company's paint materials from the bare metal to the finaltopcoat.

Wow. This is the shortest paint installment ever. Is it lunchtime yet?

The sanding dust was blown off with an air hose, then Arturo rolled theCamaro into the booth and began masking off the parts of the car thatweren't to be primered. There's a real art to this: He laid down a thin(3/4-inch) strip of tape inside the window edges to give the adhesivethat's on the masking paper something to stick to. The edges of thepaper without adhesive were taped down with 11/2-inch tape.

The Cookie Theory

OK, so maybe a little more detail is in order. For instance, why can'tyou mix paints from different companies? Paint is paint, right?

Well, no. While none of the paint manufacturers wanted to divulgeproprietary information about the chemical makeups of their products,David McConnaughey from PPG's training department put it in terms evenwe could understand.

Just before painting, he wiped the car one last time with lacquerthinner to remove any remaining dirt, oil, grease, or other debris. Thiscar had been soda-blasted, washed, vacuumed, blown off (twice), scuffed,and blown off a third time, yet there was still this much dirt on themetal. Ensuring the surface is clean is imperative to this job's successso contaminants don't come up from the metal and ruin the new paint.

"It's like buying Chips Ahoy or Mrs. Field's. They're both chocolatechip cookies, but they taste dramatically different. That's because theingredients that go into their recipes may be similar, but they're useddifferently."

Put into the context of paint, "We make a whole range of products you'llneed from the bare metal up, and we've tested all our products forcompatibility with each other," McConnaughey explained. "If you use themproperly, we can guarantee they'll work. We know our primer/surfacerwill stick to our etching primer, that our basecoat color will stick toour primer, and that our clearcoat will stick to our basecoat. Thechemistries are all compatible. If you use one company's etching primerand someone else's high-build, someone else's sealer, another'sbasecoat, and so on, we can't guarantee that all those resintechnologies will stick together.

The car was primed with PCL Poly Primer, a high-fill polyesterprimer/surfacer. Arturo added some lacquer thinner to the paint alongwith its hardener to improve its flow from the gun.

"Unfortunately, a lot of people buy paint based on price alone, and thatwill lead them to buying a mix of products," McConnaughey continued."Then if the product falls off in a big sheet, which company do you goback to with a claim? When you're using one system, if you have afailure, you can talk to one person."

Yet adhesion is just one reason you want the various paint layers to becompatible, said Brian Lynch, training manager for House of Kolor (HoK)."A migration of solvent occurs between layers of paint. We depend onthat for adhesion, since one hard shell on top of another won't adhere.But some of our colors depend on that solvent migration to move pigmentsfrom one layer to another. Pigment can soak up into the clearcoat to geta custom color. They're designed to interact with one another inpredictable ways."

Lynch also pointed out a fundamental difference between HoK paints andthose from companies whose main business is with the vastcollision-repair industry. The restoration of a factory paint job"typically won't be more than 5 to 7 mils thick," he said. A HoK paintjob, particularly one with special effects like candies, mica, or pearl,could be as much as 10 to 15 mils thick, "so the foundation has to bethat much more stable."