You might think it’s impossible to write a book about how to paint cars without talking about paint, but that is essentially what I intend to do. If it weren’t such a cliché (and if it weren’t largely untrue), I would say that the paint itself is one of the least important parts of this whole process. Yes, the surface preparation—from the bare metal to the final, sanded undercoats—is the most important element of a good quality and long-lasting automotive paint job. Secondly, given moderate skill with the spray gun (and given excellent surface preparation), the final color-sand and rub out are what make any paint job look professional and ultimately award winning. Good paint, compatibility of products and, especially today, proper mixing of the elements of each product, are all very important to a good paint job. But talking about paint is about as exciting as watching paint dry. And looking at pictures of paint cans in a book is worse than boring, even in color.
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But those aren’t the real reasons why we’re not going to discuss specific paint products here. We describe paint as solid particles suspended in a liquid “carrier” so that those particles can be transported, by pressurized air, and deposited on a surface, where they adhere once the liquids all evaporate away. That’s the way paint had been for decades (centuries if chemical compound. The other liquid you mix with it—even though it may contain evaporatives or thinners—primarily contains a catalyst, which is a chemical agent that instigates a molecular change over a relatively short period of time once the two chemicals are mixed. Today’s paints don’t just dry, they also chemically bond, which in current auto painting parlance is called “cross-linking.”
Chemistry, even though I took plenty of it, was never my favorite subject in school. So I won’t go into textbook details. But if you remember any of your high school courses, you know that in any chemical equation only so many atoms or molecules of one substance will combine with so many of another to produce a set number of molecules of the new substance. Two hydrogen atoms will combine with one oxygen atom to produce one molecule of water. No less, no more. And if you want a whole bunch of water, you must combine a lot of hydrogen and oxygen in a ratio of 2-to-1, exactly. Reactions involving catalysts are a bit different, but the emphasis here is on exact mixing ratios. To work properly, to chemically bond as designed, today’s paints must be mixed in the exact proportions specified by the manufacturer.
You may also remember that heat (temperature) has a bearing on all chemical processes. Heat is energy, and most chemical reactions require some energy to occur. In an article I did for Rod & Custom magazine in 1991 called “New Age Painting,” I quoted a PPG paint expert as saying, “With all catalyzed urethanes (clear or color), room temperature must be maintained above 50 degrees F for 24 hours for the paint to fully crosslink (harden). If not, it never fully crosslinks, and can break down with age. This is critical.” This is something I have not heard mentioned much, before or since. Good, modern paint booths are heated, and most professional painters leave a freshly painted car in the heated booth overnight to “dry” (or chemically harden). But this is pretty hard to do, even in warm climates, if you’re painting in your garage.
The worst problem is that, in most cases these days, none of this information is on the paint can. Even the type of catalyst to use, and the mixing proportions (which used to be printed in plain diagrams on the label), are often left off. Instead, you need to get a special “information leaflet” for the given type of paint, at the specific time you’re going to use it, which is filled with more precautions and legalese jargon than actual instructions on how to mix and use the product. You need help.
Then, when and if you do figure out how to use the paint product properly, the next time you go back to get some more, you are told bluntly, “Sorry, that product is no longer legal. We can’t sell it to you. You have to use such-and-such instead.” Which means, of course, that you have to learn how to use the new product. Not only that, but whatever mixing agents you had for the old product (if they had a shelf-life of more than a few days anyway) are now obsolete, and must be replaced with new, different ones. This is not only annoying, it also gets expensive quickly.
Make Friends With Your Paint Dealer
This is another major reason why we are not going to talk about specific types, brands, or product names (or numbers) of paints in this book. As I have said more than once, we are in a tumultuous, rapidly changing period in terms of auto-motive painting (among many things). Painters in many parts of the U.S. can still buy acrylic paints and reducers. Where I live lacquer is illegal, and I’ve had to change nearly all types of paint I use three times in three years. At the same time, custom water-base paints are just coming on the market, available for home-painters, but they are not perfected (at the moment they take multiple coats to cover and still must be top-coated with a urethane-type clear). I used to dread the day when I would have to paint my car with “water colors.” But the more I think about it now, I hope they perfect it quickly. If manufacturers get it figured out, hopefully the paint (once it’s on the car) will be as durable, shiny, and vibrant as anything we have now, but you could (hopefully) mix it with water, clean up with water, and not have any toxic chemicals or vapors to deal with. We’ll see.
But I can’t tell you what exactly is coming in the future. And there’s no point in talking about specific products available today, because they’ll very likely change by the time you read this. So….
We will talk about general types of paints and products that are used in the painting process (such as primers, sealers, color coats, clear coats, etc.). But to find out what specific brands, names, and numbers of those types of paints you can get, legally, in your area, at a given time, you need a knowledgeable advisor. Hopefully that is your local automotive paint dealer, with whom you should start to cultivate a friendly relationship. This is someone you’re going to have to trust.
I suppose these days you should be able to get some sort of product information from the major paint manufacturers over the Internet, but it wouldn’t be the first place I’d try. The deal is that motor vehicles are in every part of this vast land of ours—no matter where you live—and they have an amazing propensity for bumping into each other or into stationary objects. Most car and truck dealers have a collision repair shop (dealers make much more money off of repairing your car than they do selling it to you); separate, independent, collision repair shops are in every town, big or small; and a few shops around the country still specialize in automotive painting, custom or otherwise.
All of these places have to buy their paint and related supplies from an automotive paint store, whether it’s a business of its own or a corner of the local auto parts dealer. This is not a boutique business. Where there are cars and trucks, there are places to repair and repaint them, and there are stores to sell them the products needed to do so. Anyone can buy paint and supplies (and usually equipment) at these paint stores. You don’t have to be a professional or anything like that. The automotive paint stores know what products they can get from the manufacturers (what’s currently legal; what supersedes what; and so on), and they should be able to provide you with the proper catalyst/reducer, tell you the exact proportions for mixing, and what undercoats/topcoats are compatible. They need to know this, and stay on top of it, because their primary customers—the repair and paint shops—have to use these paint materials on a regular basis, and can’t afford screw-ups and redos. They know what works and what doesn’t, from using them daily. If a new product doesn’t work well, or if a certain combination isn’t compatible, they (the painters) let the paint store know right away, and demand something better.
As always—as stated in every article or book about automotive painting—the rule of thumb is to use the same brand of products for one whole paint job. The manufacturer should know, and state, what works with what. But today, more than ever, there can be exceptions to that rule, as manufacturers keep bringing new products to market, many to meet tightening government regulations.
So my advice to you is to try to find and get to know a friendly, knowledge-able, and helpful automotive paint sales-man. The easy part is that automotive paint stores are common. The hard part is that you, the hobbyist/home car painter, are not their primary customer, by any means. So don’t pester them with questions or waste their time. You might have to pay retail rather than “shop rate” for your stuff. But tell them what you’re doing, and ask what specific combination of products they recommend for the job, and what their regular customers (the professional painters) seem to prefer. Reading this book should give you a pretty good idea of what you, and they, are talking about.
One more thing, and this can get really iffy depending on which “stage” of paint job you plan, how fast you work, and how well you stick to your plans. In an ideal world, you should get all the paint products you need for one paint job at the same time. In fact, you should probably get a little more than you think you need. I’m talking about stuff that comes in cans: primer, sealer, mixed-color paint, clear, and proportional amounts of all necessary compatible catalysts/hardeners/reducers. I say this for a few reasons. First, no matter how carefully paint colors are mixed (by formula), they can vary slightly from can to can. So it’s always best to get all your color mixed at the same time, by the same person, and to get a little extra to save for potential touch-up later. If you need more than one gallon of mixed-color paint, it’s even advisable to get an extra empty can, and pour the cans of paint back and forth to thoroughly mix all the color. I’d also recommend getting an extra, smaller, empty can, say a quart, to store your leftover paint for touch-up, with minimal air in the can.
Second, get the proper catalyst/reducer, in the corresponding amount, at the same time you buy the paint. If you come back later for more, it might very well be “no longer available,” having been superseded by something incompatible with the paint you have. Further, keep these cans of paints and (especially) catalyst/reducer closed until you’re ready to use them. Most have a long shelf life, but some “go bad” within weeks—if not days—of being exposed to air (and there’s really no way to test them).
Third, these days certain primers/base coats and, more particularly, certain clears are only compatible with certain types of paints. This is where the time element comes in. If it’s going to take you a couple years, or more, to prep and paint this car and you buy all your products now, will they still be good when you’re finally ready to use them? (If you keep them tightly sealed, and in a cool place, they probably will—but check with your paint dealer when purchasing.) Probably the worst situation is to buy a mixed-color paint now, and find out after you have applied it some time later that no compatible clear is available to put over it. In a slightly different situation, I had to throw away (properly dispose of) two gallons of very expensive urethane clear because no correct catalyst was available any longer, anywhere in the country. While the natural impulse is to buy your paint color first, a better plan would be to buy your sealer and sanding primer now, because the body work/sanding process takes the longest in any paint job, and because most all catalyzed primers can be covered with any types of paint. Then, when the car all straight, primed, blocked, sanded, and really ready for paint, have your color mixed and get a compatible clear at the same time (if you’re using a clear coat), along with the necessary additives. Once you’ve done what masking is needed, it should then only take a couple days to spray the color and the clear.
Types of Paints and Related Products
Obviously we’re going to speak generically here. And since this chapter is titled “Today’s Paint Products,” we won’t discuss lacquers or enamels in any detail other than in the accompanying sidebar. Lacquers were great for custom paint jobs, but they are virtually unavailable today. Enamels are used for house paint and spray cans—though I think all house paint will be water-based soon. In short, today’s catalyzed (i.e., “two-part”) paints are far superior in numerous ways to old lacquers and enamels. Given that, we start with a couple of non-paint products that come in bottles or cans.
Wax and Grease Remover. Known in the old days by the popular brand “Pre-Kleeno,” this is a clear liquid cleaner that removes wax, grease, oils, and (today) any dreaded silicone residue that might be on the vehicle surface. Its application is simple, but specific: apply it with a clean (preferably white) cloth or towel in a rubbing motion to a relatively small area (one or two square yards), and then immediately wipe it off with another clean, dry towel before the liquid evaporates. If you’re repainting (or touching-up) a vehicle that still has paint on it, this is a very important first step, especially if it might have any traces of wax (many of which contains silicones today) on the surface. Even more obvious is to wash the car with detergent and water to begin with. Then use wax and grease remover on all painted surfaces or surfaces to be painted, including in door jambs and so on, after you have stripped the car of trim, but before you start sanding (sanding imbeds oils or silicone in the paint). Then, after all the sanding or priming, just before you’re ready to shoot your final coat of sealer or first coat of paint, degrease the whole car again. You never know what might have gotten on the car that would cause the paint to fisheye: your sweat, oil from your hands during sanding, whatever.
Metal Conditioner. If you have stripped your car to bare metal, your first step should be a metal conditioner, such as “Metalprep.” This is a mildly acidic wash (usually reduced with water) that is applied to the bare metal with something like steel wool or 3M abrasive pads to remove any minor surface rust that has formed from prior washing and, more importantly, to “etch” the metal surface to make it bond with your first coat of primer or primer/sealer. Wear rubber gloves and eye protection when applying it; follow directions carefully; and be sure to wash/neutralize it thoroughly and dry the surface before it can rust some more.
Self-etching Primer. This is one you should ask your paint dealer about. I’m not sure what types are available or applicable by the time you read this. Basically, they do the same thing as metal conditioner (other than removing rust): they chemically etch the surface when applied, so this non-sandable first primer coat really bites into and adheres to the metal.
Sealers. These were common in the days of non-catalyzed lacquers and enamels. They are applied over existing (and sometimes unknown) layers of paint before repainting. Their primary function was to act as a “hold back” shield to keep thinners in the new paint from seeping into, and possibly crazing or lifting, the old paint. At the same time it keeps old paint colors (especially reds) from “bleeding back through” the new layers of paint, causing discoloration. There were a variety of such sealers, some to be applied as a first layer over sanded existing substrate, some to be sprayed as a final layer (over sanded primer, etc.) just before the color-coat, and some used more for adhesion than for color-bleed.
High-adhesion Primer-Sealers. I said I wasn’t going to name names or numbers, but here’s the exception. When PPG introduced its DP-series of catalyzed primer-sealers more than 15 years ago, they simply called them “Epoxy Primer.” When I wrote about and tested it in ’91, I called it their “new wonder-grip…primer. This stuff adheres so well, they recommend you put filler over it, ’cause it sticks to metal better than the filler.” I still haven’t tried that, but that’s what they say, and the product is still on the market (if it’s gone when you read this, ask what its replacement might be). It’s excellent, very easy to use, and basically replaces both products listed above. In fact, without getting into chemistry, I’d call it a “double etching” primer: applied over steel, aluminum, or fiberglass, it not only “grips” the surface material, but it also grips the paint (or filler) applied on top of it. And, since it’s catalyzed, it acts as an even better blocking shield than old sealers over existing old paint, or over your own body-work and primers. So, it is excellent to use both as a first adhesion coat over bare metal, as well as a final sealer/adhesion coat when the surface is sanded and ready for color coats. Don’t sand the DP.
I mention it by name because it’s pretty much in a class by itself. It also serves as a good example of a couple of general considerations. First is to follow directions explicitly. Mix the DP with its catalyst, DP 401, one-to-one. The catalyst also acts as reducer (don’t add anything else). Once mixed, let this concoction sit for a 1/2-hour “induction” period before spraying. Got that? After spraying, let it dry at least one hour before topcoating with other paint (2 to 3 hours before plastic filler). And—pay attention—you must add topcoats over the DP within seven days, otherwise it dries (or “links”) so hard it won’t grip the paint on top of it. If you do let it go more than a week, however, you can spray another coat of DP and start again (following all the same directions, of course). I’m making a big deal of this because none of these directions are printed on the label. You’ve got to ask for the “poop sheet” that goes with the paint, and you’ve got to dig through the cautions and other legal mumbo jumbo to find the real application directions—but they are very important!
Second, like old lacquer primer, DP comes in several colors. The original, DP 40, is grey-green, DP 90 is black (which makes a great hot rod “suede primer” coat), DP 48 is white, and so on. Did you ever stop to wonder why primers came in different shades and colors? Judging from primer spots on cars from years past, apparently not. Two reasons: If you’re doing spot body or paint work on a car that’s already painted, you should cover the repair with a shade/color of primer that most closely matches the color on the car. Don’t use white or light gray primer in spots on a black or dark-colored vehicle. All paints, especially lighter colors, are transparent to some small extent. If your prepared surface has light and dark sections, these either cause lighter and darker areas in your finished paint job, or you have to spray several extra coats of color to fully, and homogenously, cover the substrate.
The primer doesn’t have to be the same color as the existing paint, just a similar shade; for instance, use light gray over yellow, tan, or silver. On the other hand, if you are going to change the color of the car significantly (or are starting from bare metal), prime the whole thing (and/or use a final DP seal coat) in a color/shade that most closely matches your final color. This makes spraying an even color-coat easier, and requires less paint. Plus, an added bonus is that when you get inevitable rock chips later, they won’t show up horribly like they would if you sprayed a dark color over a light primer.
High-Build Primer. In the old days of lacquer and enamel painting, we used lots of primer. It was usually lacquer primer, and it was technically primer-surfacer, or “sandable primer.” This is what you used, in multiple coats, block sanding after each coat, to get the body smooth, all scratches filled, and so on. Today we don’t really have any “universal primer” like that anymore (and don’t use lacquer primer under catalyzed paint—it wrinkles). Instead, we have non-sandable primer-sealers like DP 40, and “high-build,” “high-solids,” or “fast-fill” catalyzed primer-surfacers to make the job of block sanding much quicker and easier. Because they are catalyzed,(1) they “dry” very quickly for ready sanding, and (2) they also act as an excellent sealer to block against any gremlins creeping up through old layers of paint. High-solids is probably the most accurate name for this stuff, because it literally has a lot of solid material in it—a gallon of it is really heavy.
During the sand-and-prep stage, you spray on one or more heavy coats of this material, let it set, and then (ideally) block-sand most of it back off. It doesn’t clog paper; it doesn’t shrink or swell; it holds back underlying color; it doesn’t absorb water. It’s really good stuff.
The first universally popular product of this type was PPG’s yellowish K 200. Unfortunately, it (and its successor, gray K 36), have been “outlawed,” so ask your paint dealer what is currently good and available. I have also heard that a few similar products are available that are essentially “sprayable filler.” This didn’t sound good to me, and I haven’t tried it, but I have been getting very good reports on it from professional painters. Again, ask your trusted paint dealer’s advice.
Two-Part Paints. Known by various names (such as “two-pack” in England), these are any of the modern catalyzed paints, be they urethanes, epoxies, acrylics or other types, that chemically harden (or “cross-link”) rather than just air-dry. Some can be a little harder to spray, more “touchy” about fisheyes or separation, and more critical as to mixing proportions, but they are far superior to older non-catalyzed paints in most respects, as outlined in the accompanying sidebar. One draw-back to these paints (besides pervasive overspray) is that they are considerably more toxic than older types, especially those containing isocyanates. You must wear a good charcoal-filter breathing mask when applying them, and effective exhaust ventilation of the spraying area is mandatory. If you paint with it regularly without protection (a full ventilated body suit is recommended), it can definitely kill you. Then again, many two-part paints were available in non-isocyanate versions several years ago, which seem to work just as well. It’s something to ask your paint dealer.
Two-Step Paints. These are also known as two-stage (or three-stage, or more) paint, or often just “base coat-clear coat.” Whereas old lacquers were often clear-coated (with clear lacquer), the two-step generally refers to a “system” of two-part (i.e., catalyzed) paints that consists of a color base coat that sprays easily and evenly, and dries very quickly to a dull, satin-like finish, very much like the old lacquers, followed by a clear gloss-coat. Since the clear coat dries very glossy, it can be left as-is, but it is most often color-sanded and rubbed out for a glass-like finish. Whereas base coats are available in any color, including non-metallics (red, black, white, etc.), the system was designed primarily for modern metallic, or metallic-with-pearl, colors. All of these colors are available in two-part, one-step formulations (that is, catalyzed paint that dries glossy, so it doesn’t have to be rubbed out—though it could be—plus it could be clear-coated, too). But don’t get confused.
The point of the two-step system is that the usually metallic base color can be sprayed in thin, even coats without problems of streaking, running, or mottling (because it doesn’t have to be “flowed out” in a heavy, wet coat). It dries very quickly, so if you do screw up you can just scuff or sand it down and re-shoot it immediately. And the thicker, glossy clear coat not only adds depth to the color, but protects the metallic particles from being “disturbed” during the color-sand/rub out process.
A three-step paint job would include a solid-color base coat, followed by a transparent-color pearl or candy coat, followed by a clear coat. These are for advanced painters, and are only briefly illustrated in this book. True base coats, which dry satin-dull, cannot be rubbed out. Gloss-finish catalyzed metallics, pearls, or candies can be rubbed out, but it’s not recommended without a clear coat. On the other hand, I do not under-stand why painters would apply straight non-metallic colors such as red, yellow, orange, white, or especially black as a base coat-clear coat two-step process.
These colors can be ordered and sprayed in high-gloss one-step catalyzed paints, which can be color-sanded and rubbed out for an even smoother, glassier finish. Adding a clear coat (in my opinion) just means buying more paint, adding another step, and—if you’re painting in your garage—incurring the risk of a bug or dirt getting in the clear coat, which is much harder to fix than just sanding, spotting-in, and rubbing out the affected area in a one-step, non-metallic paint.
Reducers. In the old days we called these thinners. They allowed you to thin the paint to the consistency you liked best for spraying. More importantly, lac-quer and enamel thinners came in dif-ferent “speeds” (fast, medium, slow) to allow you to speed up or slow down the paint drying time, given the temperature where you were painting.
Many two-part paints don’t account for temperature; some offer a “fast” or a “slow” catalyst; others (such as high-fill primers) allow you to add reducer to the catalyzed paint, both to thin it and adjust drying time, thus making it, technically, “three-part” paint. Further, other new paints (such as color base coats) might use what is called “reactive reducer.” This does three jobs: it thins the paint; it adjusts drying time (in PPG’s current case, the last two numbers indicate its temperature range—DRR 1185 is for use in 85-degree weather); and it also contains the catalyst agent. This makes things simple for shops that spray a lot of paint daily. They can change reducer to match the weather. But the big problem for hobby painters is that the shelf life of this reducer is quite short, once it’s opened. And even if you keep the can closed, the weather might change significantly between the time you buy it and are ready to use it. Further, if you buy your mixed base coat color now, and wait to buy the reactive reducer for it when you’re ready to paint, there’s a strong possibility it might be superseded by a new product, and you are stuck with mixed paint for which there is no available, fresh reducer/catalyst. Solution? Buy your paint and matching reducer when you’re really ready to paint—and you know which way the wind’s blowing.
The above catalog is neither comprehensive nor exhaustive. We’ve listed generic types of paints that might come in acrylics, urethanes, or other chemical formulations. We’ve ignored old lacquers and enamels. We’ve also ignored strange breeds such as “alkyds” or the all-inclusive, but mysterious, “synthetics.” We haven’t explored water-based automotive paints because they don’t seem perfected yet for amateur use. We have little idea what the future holds for them, and any other new types of paints we may not have even imagined yet. We repeat: try to find a knowledgeable and helpful paint store person who can keep you abreast of new automotive paint products, and tell you which ones he or she recommends given feedback from professional customers. Further, when trying a new product, buy a small quantity and test it on something other than your favorite car, first, to see how it works and whether you like it (or, perhaps more important, to learn to use it properly).
Written by Pat Ganahl and Posted with Permission of CarTechBooks