If you are reading this then you are likely pondering what’s involved in painting a car yourself & how you can accomplish this. First of all, the good news is people are turning out professional results from their garage all over North America. The unfortunate news is that the first few jobs may not have been the show car quality that was sought after. This is no different then in the professional world, there is a definite learning curve but with some dedication and research you can learn how to turn out a show car shine before you know it.
The fundamentals of vehicle refinishing include a few parts – Body Repairs, Preparation & Painting.
This is the part of the process in which you are making your panel straight and removing dings & dents from your panel. In the case of restoration work you are typically welding new metal into place. In this article I am going to focus only on minor dent repair so look for a restoration write-up in the near future if this is your area of interest.
So a basic dent repair would consist of flattening out the dent as best as possible, then applying some body filler over it & block sanding flat. The best way to flatten your dent is using a hammer and dolly, place the dolly on the backside of the panel and hammer the front side until your dent is reasonably flat. Any high spots can be gently tapped back down if they should arise. Sometimes they are not apparent until after block sanding & at that point you can tap them down with a hammer and small pick (or screwdriver). After your metal is as straight as you can get it you should grind the area down to bare metal using a 48 grit grinding disc. Only grind the dented area and about half inch beyond. You can go over the area again with some 80 grit and take it another half inch further.
From here you will be applying some body filler. Body fillers come in different makes but are generally all polyester based that require a creme hardener to be added before use. Consult the technical data sheet for the exact specifications of the product you are using. Generally you will be adding 2-3% hardener to your filler, mix it in with a spreader until you have one solid color. When mixing it is important to mix in a sweeping motion pressing out any air pockets that can cause pinholes. It is also important not to mix on cardboard as it can absorb the resins and trap air which can be introduced to your mixture, also leading to pinholes. Once your filler is mixed you may apply it over the dent and about half inch beyond pressing down as you go. It is best to apply a few smaller skims rather then one big blob of fillers, as you may have guessed…..prevents pinholes!
After your filler is dry (usually 15 min) you may begin block sanding. You can start with an 80 grit paper until it is near perfect then switch up to a higher grit. After your body filler is straight you can apply a finishing putty over it. A finishing putty is a thinned out version of body fill that is made to sand easier and has less build. On smaller dents you can skip the body fill and go straight to a finishing putty if you prefer. Keep skimming and block sanding until you have your area perfectly straight. You always want to try and finish this stage in 180 grit paper before moving on. If you can do this with your body fill that is fine also to skip the finishing putty, just often more labor intensive and harder to get pinhole free. This would conclude the body repairs, next comes the preparation steps.
The first thing you want to do is start with a clean panel, so a quick wash with some soap followed by a good wax & silicone remove will eliminate possible contaminants from entering your paint area.Keep the water off of your body filler/metal while cleaning. You should use only an approved cleaner over these parts, usually a quick flashing alcohol based cleaner is a good choice. Now that were all clean its time to feather out our paint layers.
What happens when body work is completed you are left with a hard edge of paint,primer & clear coat from the factory spray. This edge needs to be tapered or else it will create a wave in the panel & can even sink if tried to fill as is. You can also feather out any scratches or chips you wish to repair at the same time. You should use 180-280 grit for this step and try to keep your sander flat & obtain a half inch between paint layers. Once that is completed you can get ready for primer by back sanding.
Back sanding is done so that you can prime the entire feathered area, it allows you to bring your primer beyond the feathering to ensure its covered. The only reason for back sanding is because primer can only be applied over a sanded area or it will not adhere. Since when you prime your body fill/feathering you can not control the gun that precise, back sanding is necessary. Use a 320-400 grit paper and sand about an inch to two inches past your feathering. Now your panel can be cleaned,masked and primed.
Now when it comes to choosing a primer there is a lot of options to choose from, polyester, epoxy or urethane. I will go over the basic technology of each primer & it also depends on the level of quality you want so you\’ll have to make your own decision here.
Polyester Primer – Polyester primer is typically used to get your car show quality straight. It is an extremely high build primer that is normally only applied as added security that your panel is going to be perfectly straight. The polyester primers have the highest rate of shrinkage and are developed from the cheapest resins. It should be top coated with a urethane or epoxy primer (or both) before painting.
Urethane Primer – Urethane primers come in a few different flavors, direct to metal, non-direct to metal, plastic primer. The best way to go about treating bare metal is by using an epoxy on the bare metal then following it with a urethane primer. These are fairly high build but are developed to be very easy sanding. These are often called 2k primers, they don\’t shrink as much as a polyester primer, but more than an epoxy.
Epoxy Primer – These are the best adhering primers and provide the best holdout available. They can be used a wet on wet sealer or under polyester or urethane primers. They are pretty well compatible with everything and form a bond superior to other resins. They also shrink less the the other primers. The trade off with an epoxy is that they sand terribly & are not really made for that purpose. The best place to use an epoxy is as your first primer & as a wet-on-wet sealer before your painting. (if you chose to use a sealer)
Alright, so let’s assume you chose to use an epoxy primer first then a urethane primer surface over it. After reading your technical data sheets you will know everything about the products your using and how to use them. Don’t start until you’ve analyzed every part of your tech sheet, from mixing ratio’s to flash times to gun settings..etc.
So now your primer should be dry and your’e ready to sand. You will want to apply a guide coat over your primer. It is just a contrasting color that will show your how straight your bodywork is. As you block sand the guide coat will indicate what parts are high and what parts are low. If certain area’s the guide coat remains on it indicate that area is still a bit low so continue to block sand. If you start to break through your primer it’s a good idea to re-prime it again to make sure there is adequate foundation for your paint. If you find your work is straight enough then you can skip the re-prime and go over your primer with a 500-600 grit paper to finish. You can use a guide coat over your 320 scratches to help show when you’ve successfully obtained a 500-600 finish. Now on to the rest of the car.
So now assuming the rest of your car is in tip-top shape you can simply sand the rest of the vehicle with 500-600 grit paper also. If you are not doing a respray you will need to blend your color which is outside the scope of this article. After you are done sanding it’s a good idea to follow up with a nylon scotch-brite pad to help get into the grooves and edges. You can also use it wet in conjunction with a sanding paint for an even more thorough job. After this, you can now clean up your car, mask it up and its time to paint!
One of the first things you will want to determine is whether or not you want to use a wet on wet sealer. They will provide added security to your job and produce a better foundation for your paint to be on. You can use either a urethane or epoxy based sealer. Urethane sealers are made more for speed while epoxy has quality at number 1. Check the technical data sheet on the sealer you chose (if you choose one at all). They are applied and allowed to flash for anywhere from 15 min to an hour before moving on to top coating.
The basecoat is your next step. This article will describe using traditional basecoat / clear coat, should you choose a single stage the steps would be slightly different. When choosing a brand of basecoat keep in mind that you get what you pay for. If you buy a cheap paint you will likely need twice as much so it doesn’t often put you any further ahead. After checking the technical data sheet you will know everything about the product and how to spray it. So following the instructions apply your base coat as evenly as you can and allow it to flash in accordance with your tech sheet. Use a tack rag in-between coat to pick up any little nibs that land on your panels surface. If you notice and dirt nibs they can be removed by wet sanding, check your tech sheet so you know how long to wait before attempting. When spraying always try to keep your gun straight to the panel, on metallic colors angling your gun can lead to stripping and other problems. Chose your reducers in accordance with the temperature to avoid mottling and other problems. Another thing to consider is using a hardener in your basecoat, it is an optional step usually but significantly improves the durability of your paint. Once your paint has fully covered and been allowed to dry for at least 15 minutes you can move on to the clear coat stage.
Clear coat is a urethane base coating that provides your shine and UV protection to resist fading. When choosing a clear coat you want to pick one right for the job. On larger jobs you want to avoid what are known as production clears as they dry too quickly for big panels. Once you have found an appropriate clear and as always checked your tech sheet your ready to spray. When spraying your clear it is very important to maintain a wet edge. Clear coat needs to be applied using some sort of strategy and can not go on randomly. The best practice is to go around and spray any offsets (wheel wells.. etc) then move on to your job and try to work from the top down. Try to make a starting point on a sail panel and not a larger area such as the middle of a roof or hood. The longer your clear is allowed to dry the harder it becomes to re-melt more clear into it. It’s tough to explain, let’s say you spray from the left side of the roof to the middle then take 5 minutes and try to continue from the middle to the right. You will have a visible area of clear over-spray in the middle as it will not melt in with the 5 minute old stuff just sprayed. You’ll know what I mean once you spray, maybe consider a test panel if you’ve never held a paint gun until now. If you plan on sanding your finish perfectly flat and polishing you may want to add an extra coat or even let it dry and apply another few coats, then sand and polish. If you’e happy with an OEM style finish you should be fine with the normal 2 coats.