Of all the cars I’ve painted, the only ones I’ve had no problems with, either immediately or later, were the ones I stripped to bare metal to begin with. This could be coincidence. But more likely it has to do with what lay below the surface of the dragged-home derelict vehicles that I didn’t strip. Lord knows where they had been and how many times they had been painted.
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When you’re starting a paint project you once again have a few options. First, let’s assume you know, or are pretty confident, that the paint on the car is either factory original or a respray that was done properly in the past, and there is no evidence of cracking, checking, peeling, bubbling, or so on. If this is the case, you can usually sand down the paint on the car, smoothly and evenly, and paint over it using most of today’s modern paints. If the existing finish is still relatively new and in good shape, and you just want to change the color or put something like a pearl coat over it (as we show later), then sanding down the existing paint and recovering it should be fine. Don’t forget that some new cars get damaged and spot-painted—sometimes even body-worked—at the dealer before being sold. Hopefully such work has been done properly, with good catalyzed paints, primers, and sealers. If so, it can be painted over like the rest of the car. If not, you probably won’t know it until it wrinkles or lifts while you’re painting the car. Similarly, if the original paint, or a good repaint, is just faded, or possibly the clear is peeling in places, you can sand it down and repaint it the same color (including a base coat and a clear coat), without having to repaint the doorjambs, under the hood, and so on. Further, when the car is built at the factory, the body and other sheet-metal components are dipped, electrostatically sprayed, or otherwise treated with rust-protective coats and other primers that are tougher and better-bonded than anything you can buy and spray at home (it’s the same for bodyshops or custom painters). So some painters suggest not stripping the vehicle to bare metal (especially inside-and-out, as in immersion stripping), so that you don’t remove these tough factory undercoats. It’s a debatable point.
The second—and usually better—option is to thoroughly sand whatever paint is on the car, then cover it with a good sealer followed by a modern catalyzed primer. Actually, if the existing surface sands down nice and smooth, you could spray a coat of catalyzed sealer over it (preferably a colored sealer of a shade close to the final paint color, if the sanded surface ends up multi-colored), followed by the new paint. However, most cars needing a paint job also have dings, door dents, scrapes, or other surface problems that won’t simply sand out. So most often, if you’re going to paint over existing paint, we suggest sanding it down with relatively coarse paper (180 to 220 grit), and then either shooting the whole body (preferably), or just any rough, dinged, or bodyworked areas, with a good, catalyzed, high-fill primer. If the paint on the car is multilayer, old, or otherwise edgy, give yourself extra insurance and add a coat of sealer before the primer. Then you can use some catalyzed spot putty where necessary over the primer and start block sanding, as we detail in following chapters. Most of my early paint problems, when painting over existing finishes without stripping, occurred because I was using lacquer primer and lacquer paint. We talk more about this later, but lacquer solvents are extremely aggressive, and lift or wrinkle all kinds of underlying paints, especially older non-catalyzed ones, including old lacquer. For both of these reasons, modern paints really are better, especially if you’re spraying it over existing paint.
The third option is iffy and always debatable. It pertains to older vehicles, or ones that you know have been damaged and bodyworked. But in this case the exterior surface, whether it’s fresh and shiny, old and faded, or maybe in a coat of primer, looks relatively smooth and straight and shows no evidence of cracking, bubbling, rust, or other badness. If the surface is shiny and fresh, and you want to repaint it, I can only assume you just bought the car and paid for a paint job you didn’t want. Don’t compound the issue (in my opinion) by immediately stripping this paint off only to find what you consider to be an excessive amount of filler underneath. Lots of good paint jobs, even by big-name builders, have filler under them. It’s the most expedient way to get a super-straight show-winning body and paint job. But the majority of these cars are stripped to bare metal to begin with, metal-worked pretty close, and then the filler and other undercoats are added properly. If you strip all this off, you’re just erasing several man-hours of work that have to be repeated, either by you or someone you’ll have to pay big bucks by the hour. If somebody has already spent a lot of time bodyworking, priming, and sanding the car, you’d be nuts to strip all that out and do it over again, right? Now, if there’s rust under there, or the filler’s an inch thick, it’s a different story. The body needs stripping to start, and more work after that.
But this option we’re discussing pertains to vehicles that you know or suspect have had some bodywork done, and you assume it has been done properly because nothing indicates otherwise. In such cases I suggest not stripping the car because most types of stripping either remove existing filler, or “infect” it with chemicals so it must be removed. Opinions differ on this issue, but I think it’s smarter to be an optimist. Given that you’ve checked carefully for any real gremlins, and the body looks good the way it is, sand it down and repaint it. Even if it’s a little wavy, do your block sanding on what’s already there, if it’s a stable surface. Add some high-fill primer or spot putty, as needed. But consider yourself lucky you didn’t have to go through the major job of stripping and a bunch of arduous bodywork. If you keep this car for years and it starts showing signs of some missed rust or improper body-work, either fix those spots or strip the whole car at that point, rather than assuming it from the start.
On the other hand, if you’re a true pessimist or Doubting Thomas, and you don’t know what lies under the painted or primed surface of your vehicle, there’s only one way to find out—strip it to bare metal. This is the final option, and it’s the only viable one if you know the body has too many layers of paint already, has obvious problems with existing paint not adhering to the body, has bodywork you can tell is bad (including excessive filler), or shows visible signs of rust. The only question, given this fourth option, is how to strip the body.
So Strip It
First the don’ts—please don’t take a grinder, or any kind of rotary sander, to the body to try to strip all the paint off. Not only does a grinder not reach into lots of areas that need to be stripped, but it scars the surface and actually removes metal, which you do not want to do during the stripping process. If you use a big body grinder, it not only gouges the surface, but it can also heat and warp the sheetmetal. During the stripping process, you want to remove everything except metal from the body.
A note about fiberglass-bodied cars: If you’re working on a fiberglass body, most all of the other paint processes covered in this book apply, but not most of the options for stripping—and definitely not anything like a body grinder. Some media blasters say they can carefully strip fiberglass bodies, and I’ve seen it done. But fiberglass doesn’t rust or dent, so most bodies of that type should need nothing more than a good block sanding and typical prep before repaint.
Trying to sand layers of paint off a whole body, by any means, is usually a waste of time compared to stripping. All kinds of sanders, strippers, strappers, flappers, and whatnot are advertised for removing paint, either self-powered or for use with an electric drill. Given enough time, patience, and maybe a burned-out drill or two, you could strip a whole car with one, but I wouldn’t recommend it. The same goes for any sandblasting attachments for a home air compressor that I’ve ever tried.
I once saw someone with a bag of quarters strip a whole paint job off a car with the wash jet at the 50-cent car wash. That was obviously a while ago, and it was a $29.95 paint job. If you can strip the paint off your car with any kind of pressure washer, at least you know it needed stripping.
Typical, acceptable forms of auto-motive paint stripping fall into two categories: chemical stripping and compressed air blasting with some form of abrasive particles.
Let’s start with the most serious and most thorough. It’s generally known as “immersion.” Simply put, it’s a giant vat or open tank of an acid solution (usually muriatic acid, just like you put in your swimming pool) big enough to dunk a whole car body in (actually, such strippers often have their own “secret formulas” for stripping and derusting metals that include an acid bath preceded or followed by a caustic, or alkaline, bath so that they neutralize each other; but we don’t need to get into the chemistry here). Such a process obviously requires complete disassembly of the vehicle to do it properly. I have seen one example where a ’40 sedan was immersed with its frame, suspension, and even wheels and tires still attached. I don’t know why. Maybe its chassis was so rusty nothing would come apart until they did this. But for chemical dipping to do its job, you really need to take the body off the frame, take the glass out, take the doors and trunk off—remove everything. Then the bare body is dipped and stripped and parts like the fenders, hood, and so on, are dipped separately. This is obviously a major deal for a full-on rebuild or restoration. If all you want is a new paint job, don’t do this.
But if it’s an older car that comes apart easily, if the body has lots of paint and crud on it, or—and this is probably the most serious—if this car has some real rust problems, this is your best way to go. Immersion/acid stipping is the only method that attacks and removes rust. It not only chemically removes all rust from the surface, but it also eliminates rust from the inner surfaces—even inside enclosed body areas that you can’t reach any other way. A good immersion-stripping job leaves your body and other sheet-metal parts looking like they just came out of the stamping presses, brand new. In fact, immersion stripping works very well on frames, chassis parts, and is a real hot tip for engine builders—it actually cleans out rust build-up in water jacket passages inside old engine blocks (it’s not perfect at this, but better than any other process). The only question here is what the stripper lets in his tanks—usually not a bunch of grease and oil.
Immersion/acid-bath stripping is the most thorough and easiest way to remove paint, assuming you’re doing a full tear down and rebuild of the vehicle in question (which, we realize, is only a small percentage of our audience). But, like anything, there are drawbacks. The first is trying to find one of these places. There aren’t many in the first place, and given tightening environmental regulations, the few that do exist seem to be disappearing as quickly as chrome shops. To find one, I’d suggest you search the Internet (if your phone book fails). The few that I’ve dealt with in Southern California say they have customers shipping them bodies and parts from all over the country. This diminishes the “easy” part.
Another problem with dip-stripping that seemed to be more prevalent in the past than it is now, is getting all the stripping chemicals out of body seams, joints, and other nooks and crannies, so that nothing seeps out later to ruin your paint job. Adequate neutralizing and thorough pressure washing of all parts with water after they’ve been dunked solves this problem. I haven’t heard of it happening in several years—just be aware of it, and be assured by your stripper that it won’t happen. Secondly, because dip-stripped steel parts tend to mildly surface rust very quickly, some strippers coat them with a phosphate, or other rust-preventive, as a final step. Generally, you don’t want this, because such coatings must be completely removed before painting. Either way, your first step before painting should be to use a metal-etching conditioner (i.e., Metal-prep), which also removes any minor surface rust, followed by a good etching primer. Don’t let stripped metal parts sit and rust. Don’t strip your car until you’re ready to do the rest of the job. Got that?
The final point on immersion stripping is not really a problem as much as it can be a big surprise. You may have heard of drag race cars that had “acid dipped” bodies to lighten them. The paint-and-rust removal process doesn’t remove parent metal that way, if done properly. On the other hand, your body may have had significantly more rust on it than your realized, hidden from view. If so, what comes out of the tank might be a lot less than what went in. This isn’t the stripper’s fault. That rust had to come out, one way or another. And this way, even if the body now has gaping holes in it, at least you know where the rust was. You can feel assured you got it all out and you know where you have to cut out and weld in new sheetmetal to make it right.
Once again, there are several options in this category. Sandblasting is by far the most common. Sandblasters can be found in most any industrial, agricultural, or urban area. They can quickly—and cheaply—blast paint (and other grunge) off everything from tractors, trucks, and heavy machinery to the stucco, bricks, or wood on your house, let alone the yellow lines down the middle of your street. Such places are usually not equipped or experienced to strip paint off sheetmetal on cars (even if they tell you they can). Industrial-strength sandblasting is great for frames and similar hard parts, but warps sheetmetal and also surface-hardens it (like shot-peening), which makes it harder to bodywork and more susceptible to cracking from fatigue.
Glass beading is essentially the same as sandblasting (glass is made from sand), though it’s usually confined to a blasting cabinet and used on small parts, such as cylinder heads, primarily for cleaning rather than paint stripping. Sandblasting and glass beading are both primarily high-pressure methods of stripping otherwise hard-to-remove crud off hard surfaces quickly and inexpensively.
That said, some sandblasters do know how to delicately strip paint off of automotive sheetmetal without warping or otherwise damaging it. However, I would not trust such a sandblaster unless I had a recommendation from prior customers, I could see samples of his work (if he does automotive stripping, there should be some around the shop), and he can assure that he has dry, clean sand for this purpose. Further, just because he can do a fine job on Model A fenders doesn’t mean he can do Volkswagen or (worse) new Honda or Toyota doors, which are considerably thinner metal, without ruining them. The same even holds true for many media blasters who specialize in automotive work. Several haven’t discovered yet how thin-tinned most of the new cars (and some of the older foreign ones, let alone any aluminum body parts) are. Be careful. Possibly have some “test parts” stripped first.
What you want is a “media” blaster who specifically does automotive paint removal. This can refer to most anything (in small, granular form) which, when propelled in pressurized air, is abrasive and erodes softer surfaces (such as paint) off of harder ones (such as sheetmetal). Plastic media is the most common, but “plastic” is a very nebulous word that can refer to several types of chemically derived substances. Acrylic is one you would recognize. But a good “plastic media blasting” paint stripper I inter-viewed said he used various substances including urea-formaldehyde (a synthetic resin), melamine, and even wheat starch. I’ve heard of cars being blasted with such things as talcum powder, baking soda, or anything resembling house-hold scouring powder like Bon Ami. It makes sense. As opposed to softening or dissolving the paint with chemicals, media blasting is the same thing as sanding the paint off, except you have the sand (or other abrasive) blown on with pressurized air. In fact, I had one car walnut-shell blasted. It worked fine for taking off the paint, and even existing filler, but I wouldn’t recommend it. First, such organic substances can have oils in them that they can deposit on the surface. I had no problem with that. But this one also filled the car, in every crack, crevice, and inaccessible cubbyhole inside, with a fine brown dust that seemed impossible to get completely out by blowing with compressed air, or any other means.
All media blasting leaves behind some sort of dust residue—some obviously worse than others—that has to be thoroughly cleaned out of the car before you start painting (otherwise it can blow out into the wet paint as you’re spraying). Discuss this with your media blaster. Hopefully he can use something that isn’t too “dusty,” and can get it all out when he’s done.
Another drawback to media blasting is that, while it can remove any old plastic filler, it does not remove rust. You have to do that by other means, either by grinding surface rust off, or cutting out and replacing more seriously rusted metal.
The big plus of media blasting is that it works at lower pressures (usually 30 to 35 psi for steel). Some media is said to “chip” the paint off, while being blown at an angle, rather than just abrading the paint away. Done properly, it strips paint and plastic filler off sheetmetal relatively cleanly without warping it or hardening it. In the hands of a good operator, at a lower pressure (20 to 25 psi) it can strip paint off aluminum and even off fiberglass bodies without attacking the parent surface. It doesn’t really require removing the body from the frame, or even taking off things like doors, hood, and trunk. The blaster can do an effective job in door-jambs, around hinges, and so on. And, though we would strongly suggest removing such things if you’re going so far as full paint stripping, the media doesn’t attack rubber, so you can mask off windows and other parts and leave them in place. One car I had media stripped I actually drove there and drove home; I just had to remove and replace the headlights and taillights.
Finally, such media blasters aren’t on every street corner. I think they’re more common than chemical immersion strippers, but you have to look for one that really knows automotive work. The one I’ve used in the past just closed because of environmental and city regulations, and I can’t find a substitute anywhere nearby.
So this brings us to the type of paint stripping that you can do at home, any-where. It’s also the least expensive, by far. You can do portions of the body, strip the whole outside, or disassemble everything and do it all, inside and out. But, as you’ve probably guessed, it is also by far the most labor-intensive—your labor. And we’re not just talking a lot of hard work; we’re talking messy, stinky, and potentially body-harming hard work. You’ve probably used it before on something like old furniture—liquid paint stripper, the stuff that comes in a can. You spread it on with a brush, and you scrape it back off with a putty knife once it has wrinkled up the paint. But we’re not talking hardware-store variety paint stripper, here. We’re talking the meanest, nastiest stuff—usually called something like “aircraft stripper”—you can get at your automotive paint supplier.
If you’re painting your car at home—hello, that’s what this book is about—and it needs the paint stripped for any of the reasons outlined above, this is most likely the method you’re going to use, because (1) you can do it at home, anywhere, any time (no appointments, no waiting time, no transportation); (2) the only cost is a gallon or two of the stripper itself, and it’s not very expensive;(3) you can do it yourself, using your own time and labor rather than paying big bucks to someone else (again, what this book is about); and (4) the results, if you do it properly, are nearly as good as the other methods. It’s just a big, long, sweaty, messy, even potentially dangerous job. Be forewarned. If you ask friends or family to help with this, warn them. And this is one of those procedures where you really do need to wear big, long, thick rubber gloves, full-shield eye goggles, and preferably a long-sleeved shirt. Even if you live somewhere with a warm climate, don’t attempt this inshorts and sandals. Keep a hose, with ready-running water, at hand.
Further, wherever you do this, we suggest you spread out plastic sheeting, taped to the ground, around the vehicle, or something like sheets of cardboard. Then be advised that once you start, you will get this stuff on the soles of your shoes and track it wherever you walk, so don’t go far. In fact, if you’re at all sloppy, I suggest you wear clothes, and possibly shoes, that you can simply throw directly in a big trash can when you’re done. I hope I’m making my point. I’ve done this job many times. I’m not messy. But I know exactly what it feels like when you get a spot of this stuff on your skin. It feels the same as when a welding spark burns through your shirt or falls in your shoe. Fortunately, in this case, it goes away if you quickly douse it with water. You do not want to get this stuff in your eyes. These are not idle precautions. No lawyer made me say this. I speak from experience.
All that being said, get the strongest, gnarliest stripper you can get from your automotive paint store (not the hardware store), because this job does take time—inevitably more than one application, maybe two or three—and you want the stripper to work as quickly and deeply as possible. But let the stripper do the work. Be patient. Pour some stripper into something like a big coffee can. Brush on a good, thick coat of this stuff (with about a 3-inch, bristle-type, old—or disposable—paint brush). Then have a lemonade; do a load of laundry; make some phone calls. Let the stripper wrinkle, bubble, and lift the paint. Give it time. Don’t start scraping until it does.
If you’ve gutted the car, you don’t have to worry much about masking things. A big plus of this stripper is that, though it can run a bit, it basically goes where you brush it. It won’t leave dust or other residue, and it won’t get into places you can’t see to wash it out. It does not attack rubber or chrome, just as it does not attack the metal you’re cleaning. While we, of course, suggest removing everything practical from the body before this type of stripping, you can leave the windows in place and mask them off (with good masking tape and paper), and leave the doors (and hood and trunk, if applicable) shut, and strip the car that way. Then, if you’re going to paint the doorjambs and so on, remove rubber weatherstrip and hand-sand those areas. Or, if the jambs have as much paintbuild-up as the rest of the car, you can mask off the interior and the insides of the windows to strip them, too (actually, the stripper won’t hurt glass or rubber, so you don’t really have to mask off windows; but you don’t want stripper running onto wires, power window motors, etc.). If you want to do the best-quality repaint, however, remove all glass, handles, and so on, so you can remove all paint under them and their seals. To keep stripper from running inside the body, tape any holes from the inside with masking tape.
Further tips for “hand liquid stripping”: Do not apply this stuff in the sun on a hot day. You don’t want it to dry out before it does its work; in fact, you don’t want to let it dry out at all. If you see any areas drying, possibly because you put the stripper on too thin, just brush on some more, then wait for the paint to wrinkle. Conversely, like most chemicals (including paint), it works slower the colder the ambient temperature is. I don’t suggest doing this in winter in Detroit, even if you do the stripping inside a warm garage. The final step is washing all traces of the stripper and old paint off the body with running water and scouring pads. You probably don’t want to do this inside the garage, and you don’t want the water freezing on the car in the driveway.
One trick I’ve heard of for warmer climates (but have not tried) is to brush the stripper onto the whole car, then cover it with a layer of clear plastic sheeting (like Visqueen). This keeps the stripper from drying out, but allows it to get hotter and work faster.
When you’ve given the stripper plenty of time to work, and at least one or two layers of paint have wrinkled up, it’s time to start scraping. Assuming you’re working on a metal body (steel or aluminum, it doesn’t matter), I suggest using a long-handled putty knife or flat-blade scraper to start removing the now-softened paint. Just remove the paint that’s ready to go. Don’t try to force or gouge it with the scraper. If you get down to bare metal in one application, you’re really lucky. Otherwise, brush on another thick layer of stripper and let it go to work again.
Once you do get down to some bare metal, there will still be lots of traces of paint on the surface. For getting into corners and crevices, I’d suggest using a short-bristled wire brush. Do not use a rotary wire wheel, or anything like that; even a regular wire brush with inch-long bristles inevitably flings some stripper on you (or something else nearby you don’t want it on). This stuff is nasty. Be careful.
Finally, to get the last specks and streaks of paint off the body, give it one more coat of stripper, let it sit a while, then start scrubbing it off with steel wool or, preferably, a coarse 3M Scotchbrite pad. When you’ve got all the paint off, continue with the Scotchbrite pad with a hose dribbling water, which not only washes off all remaining liquid stripper, but also neutralizes it. Dry or air-blow the car down before it surface rusts, and you’re done. Carefully roll up and dispose of the plastic or card-board you put down to catch the scraped paint and drippings. Thoroughly spray the work area with water from a hose to wash off and neutralize any stripper that may remain on the ground. If any small spots of paint were missed, they should easily hand-sand off. And if you didn’t strip areas such as the doorjambs, hand-sand them, being sure to feather any edges to bare, stripped metal.
Of course you want to prep the bare metal before painting, starting with Metalprep or an etching primer/sealer. One final caution: if you see streaks or splotches in your first coat of primer that appear not to dry, that means some of your stripper remains on the metal. You don’t want that under your paint. So you have to restrip those areas or, preferably, sand them back down to bare metal. The sanding will probably remove any vestiges of stripper, but a rescouring with Scotchbrite and water wouldn’t hurt. Better yet, give the car a double scour/wash with water when you’re done stripping to be sure you’ve got all the stripper off before you start the paint process.
Written by Pat Ganahl and Posted with Permission of CarTechBooks