How To Repair Paint Flaws without Respraying
Whether you want to paint your own car to save money, or just for the satisfaction of doing it yourself, you should know what you're up against before you begin.
Many amateurs make the mistake of believing you have to completely prime the whole car, which isn't necessarily the case. It isn't a bad idea, just not 100% necessary. If you're painting the whole car, a nice even coat of primer will give you a solid base to spray over, which will result in even coverage with less paint. Any area that has had bodywork, or where bare metal is exposed, must be primed before painting, but paint will adhere just as well to sanded paint.
There are many different types of primers ranging from general purpose primers to special primers for specific needs. Ask where you buy your paint to find out what will work best for your project. You might find yourself using an etching primer on bare metal, and a different primer for a full coat, or over filler. Ask at the paint store to make sure there are no compatibility issues.
Compatibility with paint is very important. Generally if you stick to one particular brand for everything from primer to clear coat, you should be fine, but it never hurts to ask just in case. You don't want to spend weeks getting the body perfect, and hundreds of dollars on paint, only to have to paint wrinkle because it reacted adversely to the primer.
Priming a car can be good practice for using a spray gun. At this stage you don't have to worry as much about getting a run, as they are much easier to sand out in primer. Also primer generally dries faster so you don't have to wait long to be able to sand out the problems. Some primers require a light coat over areas that have been sanded, others you can sand and apply paint directly over. Reading the instructions that come with the primers and paint products is very important at every step of this process.
Now that you have the car in primer, all sanded and cleaned, you're ready to start painting, right? Wrong! You've probably been doing the bodywork in your garage so move the car out and clean up.
Since most people don't have easy access to a fancy professional spray booth, this article is based on the assumption that you will be spraying your project at home in your garage. You have to treat your garage just as you would a paint booth because that's what you're using it for. Clean out all the dust-collecting items in the garage and then clean the garage itself. Sounds like common sense but many people overlook this important step and end up with a dust covered paint job and an angry wife because you got overspray on the Christmas decorations that were stored in the garage. Try your best to avoid both by doing a thorough clean-up. Wet the floor with water and move the car in.
Before spraying, make sure the car is clean. The cleaner the better. Use an air blower to ensure all gaps between panels are free from dust that might blow into the paint while spraying. Then use a good surface cleaner and clean cloths. Avoid touching the car from this point on as the natural oils in your skin can cause problems in the paint.
After an initial cleaning, mask the car if you haven't already done that before bringing it into the booth. Be sure to not leave any folds in the masking paper that dust or paint mist can gather in. Tape these up. Now do a second cleaning with cleaner and new cloths. Don't re-use the same ones because you may spread contaminants from the previous cleaning back onto the surface. Most surface cleaners are applied with one cloth and wiped off with another. When you're finished cleaning, go over the whole car with a tack cloth. It may look clean but the tack cloth will pick up the really tiny dust left behind. After tacking the whole car, give a light tack to the masking paper as well just in case there is any dust on it. You don't want that blowing into your paint job.
Now that the whole car and booth are ready, add the reducer, hardener, etc. to your paint following the manufacturer's instructions. I suggest taping a piece of cardboard to your booth's wall to use for test spraying. Adjust your air pressure according to the spraying directions, fill your gun using a funnel cone filter (or similar type of strainer), and test how the gun sprays on your cardboard. Once you're happy with how it sprays, start on the car.
Many beginners have difficulty keeping the air line off the paint. If you think this might be you, and your garage is big enough, have someone join you to watch the hose. Make sure you are both wearing respirators suitable for spraying paint.
I recommend starting spraying on the roof. Work your way down to the hood and work your way around the car. When you get back to where you began, the first coat is finished. Remember that the object is not to get full coverage in one coat. Don't be tempted to spray it on heavier to get better coverage. Multiple light coats are far better than one or two heavy coats. Usually three or four coats will achieve the coverage you desire. This is art, don't rush it!
Flash time is the time you wait between coats of paint. If the instructions say the flash time is 15 minutes, wait the full 15 minutes from the time you finished the first coat. Then start the second coat. Start each coat from the same place. That assures even flash time on each part of the car.
If you're spraying single stage paints like acrylic enamels or urethanes, you'll be done after the three or four coats of color. If you're spraying base coat/clear coat (my favorite), you'll have more spraying to do. Waiting time between base (or color) coats and clear coats is usually longer than the flash time between coats. Check the paint manufacturer's instructions for proper waiting times at this stage. I usually wait an hour at this stage, longer in cooler temperatures.
One trick I've learned is to make the first coat of clear a light one, followed by the recommended number of coats of clear (as per instructions). The norm is three coats of clear but I recommend adding an additional couple of coats of clear. This allows additional build-up of clear that can be wet-sanded later. The reason for this wet-sanding is to eliminate flaws in the finish, such as minor dust, some runs, and orange peel. Part two of this article will discuss how to use this technique to repair those flaws you may have thought were irreparable. For now, lets get the paint on the vehicle. We'll worry about fixing problems later.
Once you have finished your final coat of clear, walk away. You may be tempted to go back repeatedly to admire your handiwork, but this can raise dust from the floor, or you may accidentally rub up against the wet paint. Avoid the temptation & stay away until the following day.
After letting the car dry overnight, you can go out and remove the masking tape and paper so you can inspect it and see what a great job you did. Remember that fresh paint is soft. You can rub your hand across it once it's dried overnight, but if you press your finger against it, you will likely leave a lasting impression. A friend of mine painted his car and the next day leaned against the fender for a picture with his pride and joy. It left an impression of his jeans in the paint.
OK, so what do you do if someone leans into your paint? What if you got some minor dust, runs, or over-spray in the finish? Relax... you can fix that without having to repaint. More importantly, you can turn that "decent" paint job into something to be proud of.
First of all, you will want the paint to be good and dry before attempting any repairs to the finish. I recommend 24-48 hours to allow the paint to dry before wet-sanding and buffing. Sitting around waiting for paint to dry will give you the opportunity to return to your local paint supply store. You will want a sanding pad designed for wet-sanding (I use 3M part #05526), and some sandpaper made for wet-sanding. The wet-sanding paper you will want should be a minimum of 1,000 grit, but also buy some 1,500 grit. Some people take it a step further and use 2,000 grit or even finer (higher numbers equal finer grit), but I find you can get amazing results with 1,500 grit sanding. You may think the word "grit" is misleading because of how fine these papers are, but make no mistake; they will sand the paint surface. Also on your shopping list will be an electric buffer, preferably variable speed, and not a polisher ï¿½ there is a difference. A polisher is typically used for the application of wax and polish, where a buffer is for rubbing compounds as well as polishing.
I use an assortment of rubbing compounds, but a medium cut and fine cut compound, followed by a finishing polish should suffice. Rubbing compounds and finishing polish require different pads on the buffer. Asking at your local paint store will get you the right pads and compounds for the job. Personally I use 3M compounds and polish, finishing up with a 3M product called Final Inspection. This is a spray-on, wipe-off application that will remove the haze left over from buffing. If you're buying a different brand, ask for similar products in whatever brand they sell at your local paint supply store.
Starting with the 1,000 grit wet-sandpaper, on your hand-sanding pad, you'll want to begin with the roughest areas on the paint first (the areas with the worst flaws). Have a small pail of water with you and keep the sandpaper wet by dipping it often into the water. Some people prefer a spray bottle or a hose trickling, but whichever method you choose, the important thing is to keep the surface and the sandpaper wet.
Once you've sanded out the larger imperfections with the 1,000 grit paper, and have it smooth, go over the whole car with 1,500 grit paper. This method will remove minor dust, many runs, and even orange peel. Sand in a different direction each time you change grits. This will eliminate sanding scratches left from the 1,000 grit paper. For those of you who may not be familiar with the term "orange peel", it refers to the bumpy texture of the paint. It has nothing to do with the color orange. If you examine the surface of an orange, you will see small bumps or dimples in the surface. Paint often has a similar finish, thus the name.
Painted surface as as you begin to wet-sand out the orange peel.
If you lightly wet-sand an area of your paint and dry it off, you will notice light and dark spots. This is because you're sanding down the high points of the orange peel bumps. Once you've finished sanding, the surface should be completely smooth. You're actually sanding off some of the clear coat, which is why you applied those extra coats of clear when you painted. It's vital not to sand too far, and use extra caution near the edges, corners, and bodylines.
The orange peel is gone.
Excessive orange peel and run in door.
Sanding out run in door. [Note: the color shift is caused by our cheap digital camera]
Run almost gone.
After buffing, there's no sign that the run ever existed.
Now back to the rest of the car
Now that the car has been wet-sanded with the 1,500 grit wet paper, you'll notice that there is no shine to the paint. This is normal, and usually the point where most people think they have to spray on more clear. I wouldn't do that to you. Let me explain how to get that shine back, better than ever. Wet-sanding a whole car is a time consuming process but the end result is well worth it. Once the whole car has been sanded and dried off, you are ready to buff it. Perhaps I should say it's ready to be buffed. Whether or not you are ready to buff it remains to be seen. Buffing a car with new paint is trickier than it looks, especially if you've never done it before. If you have access to an old car or body panel (like a hood), I suggest practicing on that first. Fresh paint is a lot easier to damage with a buffer than cured paint.
Closeup of runs around door lock area.
Wet sanding around the door lock area.
When you wet-sand a car that has been clear coated, it turns white as you sand. Many people expect a dark green car such as this one to be dark green when sanded, not white. The white is because you are only sanding the clear coat. The color underneath remains untouched, provided you don't sand too far.
The car has been reassembled and wet sanded.
Some people prefer to apply compound directly to the buffing pad, where others prefer to apply it to the car itself. There is no right or wrong in this, it's simply a matter of preference. I apply it to the car and spread it around with my hand, then buff. I find this creates less chance of compound getting flung around as the buffer spins. Either way you apply the compound, work in small areas, like two feet by two feet or so. Working in a larger area increases the chance of the compound drying, which makes it considerably harder to buff off. Also do not work in direct sunlight. You can do your wet-sanding outside in the driveway, but bring the car back into the shade of the garage when you buff, or wait until there is shade in the driveway if you want to do it outside where the light is probably better.
I suggest three applications of each compound, starting the buffing process with the medium cut compound, and then fine cut. Do the whole car once (or at least the whole panel), and then give it a second pass, and a third. You will start to see the shine come back from the first pass with the medium cut compound but we're going for mirror finish here, not just sort of shiny. Friction creates heat which will damage the paint, so keep the buffer moving and don't apply much pressure at all. Let the machine do the work! I hope you beginners practiced on an old hood like I suggested.
After you have finished with the rubbing compounds, switch pads and use the finishing polish. Again I suggest three applications of this. You will notice the car is covered in a haze at this point, which is where the Final Inspection spray comes in. You've made the paint shine by buffing it, now clean it with the Final Inspection spray and wipe it off. Often once is enough, but if there is any remaining haze, go over it again with Final Inspection.
Now you have a very shiny car that you can tell everyone you did yourself. If you're thinking a good coat of wax will make it perfect, you couldn't be more wrong. Paint manufacturers generally agree that you should avoid waxes for at least 30 days. Wax will seal the paint so that potentially harmful contaminants can't get in, but they also prevent the solvents in the paint from evaporating, which they need to do. You can wax your car if you like, but wait at least a month before doing it, or you will ruin the new paint. Other things to avoid in the paint's first month are car washes and pressure washers. Car washes have brushes that can damage new paint. Even touchless car washes use water under considerable pressure, just like a pressure washer. It should be obvious that blasting water or anything under pressure at new paint can't be good for it. To wash your car, I suggest a garden hose with only gentle pressure, a soft cloth designed for washing cars, or a sponge, or car wash mitt, and car wash soap.
See you at the car show!