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Category: Repair Articles
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Published on Thursday, 03 November 2011 21:43
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Written by Justin Jimmo
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Hits: 1291
***please note the following is preparation notes for a video. it is intended to line up with video and other visual aids, it should still be of use to read but anywhere I've made a reference it may not make much sense on its own***
Hey guys, jimmo here with refinishnetwork. Today I have put together the most comprehensive repair video you will find on the net, start to finish completely free. I am going to give a complete breakdown from dent repair all the way up to painting. Now we'll cover things in between such as blending clear, using waterborne paint, aerosols and many other what if scenario's. So theres a lot to cover, let's get started.
Now, its best to look at this process in 3 parts, bodywork which covers dissasembly, metal, plastic or other material repairs, which would also include Dent repairs.
Second comes prep, this would cover feathering, priming, sanding, blend panel preparation, masking and a final inspection.
Lastly comes painting. This of course would include spraying the necessary products, base and clearcoat and sometimes non sanding primers.
So to get ready for your repair, the best practice is to wash the car down entirely with soap and water, followed by a solvent based degreaser. I'm sure they're is water based degreasers available and if you come across one designed for this use then by all means use that. Once the cars clean you have a good opportunity to check it over and make sure you mark out any damage you see and intend to fix.
So theirs one last step before we start sanding, remove any trim items on the panels we'll be working on. Now I'm going to have to jump ahead here for a second and talk about blend panels and then we'll come get back to it..
When you get the paint from your supplier the odds are it will not match 100 percent. In the case of a metallic color the even if you were given an identical color you would have to know the specific pressure, distance, tip size and temperature it was sprayed at. It sounds far fetched so I'll show you an example. These sprayout cards were sprayed with the same paint, half at high pressure and half at low. The light part of the card is where the paint landed dry and the metallics reflect closer to the surface, the dark where they went on wet and sunk down. So the bottom line is to achieve an undetectable match we must blend our paint out. If you do not have enough room within one panel you will need to take your color into the next. So that begs the question what is enough room? Unfortunately they're is no magic number for me I like to have about a foot minimum, for someone starting out they may need 2 to 3. Many factors come into play, solid and dark metallics are fairly easy to blend while light metallics such as silvers and golds are more challenging, I'll cover more about that later but at this point you would need to decide if you need another panel to blend your paint into so you can complete your disassemble. Ok back to the body dept.
Okay so now that your up to speed on blend panels, you'd want to go ahead and remove any trim from the repair and blend panels. Now every car comes apart different so I can't cover this, best advice I can say is try a google search any you can probably find somewhere in cyberspace. You'll want to take off mirrors, door handles, molding,etc.you can in some cases just loosen or you may need to completely remove bumpers. Now can you tape these pieces up? Sure ya can but you won't be able to sand the edges well and run the risk of paint peeling in that area as well as damaging or getting over-spray on the trim, so you'll have to use your own discretion on the job at hand.
So time to start the repair, we have a simple dent here were going to apply some body filler into, so to get it ready we need to sand the area down to the bare metal. We want to remove the paint from the dent and slightly beyond. In the case of a larger dent we'd use a grinding disc but on a small one like this we'll use 80 grit paper on a dual action sander.
Now you can do this by hand if you like but I strongly suggest you get a hold of one of these. They call it a dual action sander because it moves orbital but also up and down which leaves the surface with an even and consistent sanding. you can possibly get them in electric but in the professional environment we use pneumatic or air powered tools which is more cost effective because each tool doesn't require a motor, they run cooler and can be made lighter. Ideally whatever your setup is an air compressor is a necessary if u plan on doing this often or want your work to turn out as good as possible.
So after you've removed the paint you can go ahead and apply your body filler. In this case we are using a light filler, or what's usually referred to as a finishing putty. Its a thinned out body-filler used as a final skim over heavier dents or useful to fill minor dents like this. It will generally sand easier and go on smoother then a heavier body filler. So let's get you up to speed on different types of fillers. Starting from the high end of fillers you'll find fiberglass filler which is used for severe filling and useful for large restoration jobs and some collision repair jobs. The benefit of it is its stronger, but it also does a better job of waterproofing the repair from condensation in the air. It utilizes glass fibers rather then talc found in regular body fillers which can hold moisture, more problematic if it sits on the vehicle without a primer for an extended period of time. The downside of fiberglass is it sands harder and more difficult to shape. It comes in short and long hair, the long hair isn't overly practical and is more difficult to work with.
Next we have our regular body-fillers which are most commonly used for large dent repairs. Most of them utilize the polyester resin however you may find other ones such as evercoats maxim line that uses an epoxy resin designed to sand easier. They are made to go over bare metal and generally adhere best to grinder scratches.
Finally there is a finishing putty, may come across it as a glaze. In any event its a thin version of body-filler designed as a last coat or where small filling is required. It is also useful for filling pinholes. Now pinholes are small air-pockets created from mixing the filler that can appear and are more visible once its painted, so make sure you look for them and fill them before the priming stage.
Your find all kinds of specialty fillers, aluminum, ones applied threw a gun... I can't really touch on them all so let's move on to mixing.
Now any filler you'll be using should have a hardener with it. If your unsure of the mixing ratio go to the manufacturers website and look up the technical data sheet or tds to get the proper information on the product. If the sheet contradicts anything I'm telling you then just follow products tech sheet instead.
In my case using 3m's flowable putty I need to activate it by adding 2 percent hardener. To get more accurate of a mix you can do it on a scale. So you will then take your spreader and mix in a downward pushing motion and what this will do is squeeze out any air and keep pinholes from forming. Another thing to keep in mind is try and mix on metal or a board designed for mixing. If you mix on something like cardboard, being porous it will introduce air into your mix creating pinholes, and also cardboard is often coated with a wax-based waterproofing substance that will dissolve in your filler and contaminate it.
You will have maybe a minute to apply depending on temperature and humidity, so on a larger job only mix up what your have time to apply. You will want to gradually apply in a few smaller skims rather. Then blob it on all at once. Apply it a bit beyond your dent, its ok over the paint a bit because you'll likely sand it back in the next step.
It will take about 5-10 minutes before its ready to sand, feel it. Once its hard you should be able to tell pretty easily. Now were going to use 80 grit paper to make our first cut and when we get closer you will ideally want to finish sanding no coarser then 180. So start by placing your sandpaper onto a block and sand the filler by applying a bit of pressure but not pressing too too hard. Come at it for every direction, a few strokes up, down, sideways, diagonally.
Now when the filler is fairly close and starting to feather out you'll want to switch to 180, you might be better to switch to 120 a bit sooner and gradually move down. At this point it can be beneficial to apply a guide coat, so let's pull you up some information on that.
A guide coat is a paint of coating, in this case a graphite powder that is applied to a primer or filler to help spot out high and low spots. When you block sand a panel the high spots sand first and the guide coat is removed, where the guide coat remains it tells you that area is still low and requires more block sanding to level it. So essentially a guide coat is a visual aid for leveling and refining scratches. A contrasting colored spray paint will work for this too.
So we'll finish sanding our filler until we run our hand over the dent and can't feel it. It may take a few trys to get it right so if you need to, reapply the filler and try again. Also we want to check the filler over for pinholes, if you find some apply a really tight skim of putty and sand it level before moving on.
So that's it for the body section, next we move onto prep.
So the first thing we want to do is feather our paint layers. At this point you likely have a sharp transition in the area the paint was removed. So what u want to do is separate the paint layers by sanding to create a gradual taper. Now ill be using a sander but a block will get it a bit straighter. According to basf, they suggest to visualize it and begin sanding from the outside and gradually moving it. They suggest that going from the inside out peeling the layers back creates a torn edge visible under a microscope that can lead to visible rings when the paint cures. I received that information after doing this job and its probably how 99 percent of jobs are still feathered today.
So you can use 180-320 grit paper here, when your trying to preserve blending space I'd suggest trying to use 320 because you will need to apply a primer over-top of a 180 scratch.
Next we will need to get this area ready to apply a primer or better referred to as a primer surfacer. So to do that we need to backsand the repair. We know that we need to apply the primer surfacer to the feathering and anything inside but the guns gonna end up spraying slightly outside that area. The primer won't adhere well applied to non-sanded paint, so we back-sand slightly beyond so our primer sticks. So you wanna grab some 320 grit paper and sand a few inches beyond your feathering and/or 180 scratches.
Next blow it off and wipe it down with a cleaner, I like to use a solvent or alcohol based cleaner at this point. Mask it up to keep primer over-spray from getting on the next panel and were ready to prime. You'll notice I don't tape a solid line around my repair, you do not want to make a sharp line made of primer or you might see a visible line when your done, play it safe and give yourself a bit of room here. Another option on small area's is taking a piece of cardboard, cut a hole in it and spray threw the hole about an inches away from the panel.
So now we are onto choosing a primer, so let's get you familiar with the different primers available.
Now, even I've been tossing around primer and primer sufacer around interchangeably. Most often when I refer to primer I'm speaking of a primer surfacer. A primer surfacer is designed to not only protect the repair area from corrosion but also provides filling so we can block sand it one more time to level the feathering and any other minor imperfections.
Now primers come in 4 main categories that refer to the resin used to hold it together.
Epoxy - which is known as one of the strongest resins, superior corrosion protection but slow drying. It is often used as a protection coat on bare metal under a urethane primer but it can also be used as a primer surfacer. Generally it doesn't build as well as urethane.
Urethane - this is what I'll be using on this job. these primers probably comprise the most popular part of the market, they are designed to dry fast and sand well. For the most part they are only used as a surfacer for filling. They come in various styles, if your doing a job like this you want to ensure your using on that's approved to use over bare metal, otherwise you'll need to apply a precoat to your bare metal.
Etch primer - this primers sole purpose is to protect metal. it is an acid based product the bites into the metal and provides protection, you would need to apply a primer surfacer over this. Etch primers vs epoxy I can't say which one is better, but on a large job you would want to pick one as a precoat.
Polyester primer - this is mostly used in restoration work but some collision guys use it. Its pretty well sprayable body filler. Its super high filling and cheap. Some are made to paint over, some are not. Its usually used to get a panel looking as straight as humanly possible, but for small repairs its completely unnecessary.
Lastly you'll find lacquer primers. For the most part u see them in aerosols
Now you'll find other specialty primers along the way such as plastic primer but I'll have to save that for another video.
Next thing you'll find is lacquer based primers and surfacers. Now there commonly found as aerosols but you can get ones designed for spray. The problem with lacquer based products is they are simply air drying products. All of the previous products mentioned require a hardener that creates a chemical cure which makes them much more durable. Avoid using lacquers at all if you can.
So back to spraying, you will hopefully be using a gun. For someone starting out I highly recommend getting the 3m accuspray. It can utilizes disposable tips that come in different sizes for priming or paint, I've even cleared with it and had great success. Now if a gun isn't an option for you, in this modern age they've developed 2 part aerosol cans for primer and clear coat. These cans have a button which injects the hardener prior to using. I've done a fender complete with them and had success with it but if you can look into a gun, the accuspray is a great investment especially starting out and is priced well. You should note that you will need to also use either the 3m pps paint mixing system or a compatible system to make the gun work, it does not have a hard cup but it makes cleaning it very simple, especially if you don't have a gun cleaning machine.
So moving on, after you've mixed by following the mixing ration, on the tech sheet for whatever product your using, yes tech sheets, remember them on your product manufacturers website. You've got you primer mixed and loaded your gun. Spray it a bit beyond the feathering at about 25psi or the specifications found on your tds.
Give it about 5 minutes before applying your next coat or go by the guidelines on your tds known as flash time, which refers to the amount of time for solvent to evaporate.
Apply your second coat and if necessary, a third. Now each coat you want to bring inward so your not priming over top of the previous coats dry over-spray. The old way was to go the opposite way but since been discovered that it can result in sinking which would appear as visible rings in the finish, weeks later as the paint fully cures.
So I'll be using my infrared lamp to bring my drying time to about 10 minutes, otherwise your gonna be waiting a few hrs typically but check your tech sheet and you'll know for the product your using. So when its dry we will give it another block sanding with 320, but first apply a guide coat like we talked about earlier. Once you've sanded the guide coat away, apply it again and finish sanding in the grit specified on the technical data sheet for the paint your using. In my case its 600 here, if it were waterborne basecoat it would be likely finer, but depends on the manufacturer.
Let's jump ahead for a second and talk about the option for a singlestage.
A singlestage paint is one where the color and clear are combined in one mixture, its more practical on a complete respray or fleet vehicles. Its a durable finish however usually has less uv protection, meaning the sun fades it quicker. It can be a more cost effective solution in some cases, but generally speaking you want to go with base/clear. Blending singlestage is not an easy task, it is the same as blending clearcoat and runs the same risks of the sun breaking down the edge where its been blended. I've covered blending clearcoat in other video's so you'll have to check them out because the prep is slightly different. Metallic singlestages I wouldn't recommend for anybody, I've yet to see a metallic singlestage I'd ever want my name on. Door jambs, cut ins maybe but exterior, I would never consider.
so I'm going to finish this with a dual action sander, it leaves a consistent scratch that's great for our paint to adhere to. You can sand by hand if you like or even wetsand at this point.
Next check the area around the primer for overspray, you should be able to feel it too. It will be gritty and can be removed with whatever sandpaper you'll be preparing your blend panel with.
So you have several options here, but first check your paint manufacturers recommendations and try to align it with this. I like to go wet here but you can do this dry or even with a sander. Here I've simply chosen to use a nylon pad which can be thought of as sandpaper with a paste that works to clean the panel and keep the pad cutting better. Another typical method would be to sand the panel with something like 1000 grit or finer and just scuff the edges with a pad. You want to be careful here not to sand the edges to hard or it will require paint, something you don't want to have to worry about on a blend panel.
Once that's complete we simply dry it off if your wetsanding and the last step of prep which is masking.
Now generally with masking you want to start from the inside and do your door jambs first, then move to the outside. Now I'll talk about a few specialty tapes for jambs. 3m makes one called a transition tape and it has a thin flap of plastic that works soften the paint edge, its best attached to a bend. Next you have a foam tape that also softens the edge, but not as effectively as the transition tape. You typically want to attach a piece of 6 inch paper taped inside your specialty tape. You can skip the specialty tape if you choose to but you'll end up with a hard tape line in that area, I have seen people fold the tape a 1/4 inch and somewhat simulate what the transition tape does. Mask inside area using 6 inch paper as well. Masking jambs is a pretty broad topic but ideally you want to ensure you don't end up with over-spray on your jambs.
Moving to the outside. You can use paper or plastic, just make sure you've cover the entire car because the clearcoat creates an overspray that will stick to anything around it. Don't forget to mask your wheels and if your using waterborne paint you will need to use a water resistant paper.
Ok so were almost ready to spray, so let's give it a wipe down with preferably a waterborne cleaner, followed by an alcohol based cleaner. The reason we choose these is because the water doesn't generate static and cleans most contaminants away, the alcohol cleaner can remove static and removes mild oils such as fingerprints that may be on the panel.
So its time to get the paint ready, but first I'm going to apply a non-sanding primer, more commonly referred to as a sealer. What this does is improves holdout by creating a better foundation for the paint. It is optional and we could skip it here without a problem. Some sealers and primers can also be tinted, what you want is the value (lightness/darkness) to be similar and you will need less paint to cover it, don't worry about the hue or color because it doesn't impact coverage.
So the sealer gets applied somewhere between 25-30 psi in accordance with your tech sheet. You want to have it go on as smooth as possible but don't run it! When spraying try to achieve a 50 percent overlap.
So its time to put color on and before I go any further, I want to stress the imprtance one more time of your tech sheet. Its gonna give you equipment recommendations such as tip size which you should follow as closely as possible.
So get your base ready, adding a hardener will improve the durability of the paint but in basecoat is generally optional. So unless your using a mixing system pour any products threw a strainer into the gun.
The next optional step is applying an orientation coat or if your using waterborne they call it a wetbed. You can apply either at the first coat or right before your last coat, or both and you can also blend your color threw it while its wet which keeps the basecoat from landing dry. Now this is only beneficial on a metallic color. Solids and dark metallics don't require this.
So its going to be applied the same way as we'll spray our paint. About 6 inches from the panel and medium wet,so not too light but now soaking on either. You can apply this over the entire job or just over the blend area. Before spraying you should wipe the panel down with a tack rag, which is simply a cloth designed to pick up dust and anything that's ended up on your panel. You can tack in between coats after its flashed, ideally you want to use it at minimum before you start spraying and before you start clearing.
After the product has flashed it will go from shiny to flat looking both with water and solvent based paint. Then we can start spraying the color. the first coat covers the primer or sealer and gets slightly fanned out to help blend as we go. Each coat requires flash time and if your using waterborne paint you can use specific air blowers to speed that up.
So bringing out each coat and fanning it out will blend the paint naturally, however with metallic colors some common challenges are:
Halo'ing - the edge where you blended out the color is light in color and visible. This is because the edge lands dry and reflects light while the rest landed wet and reflects dark. You can try dropping your pressure or applying another orientation coat or wetbed and blend another coat of paint into it while still wet.
Mottling - where the metallics bunch up and give a patchy look. Its more problematic on a horizonal spray such as a hood,roof or decklid. Try reducing your pressure and increasing your distance and try to spray as even as possible. This can help with striping looks too.
Spraying light metallics is hard and takes experience to really get the hang of. But let's assume we've applied the basecoat to our liking and are ready for clearcoat.
Now the base should be left to flash at minimum 15 minutes before applying clear, again check your tech sheet.
Clearcoat is another urethane based product that's primary job is to provide the shine, resist fading and protect the finish. Its only as strong as the prep-work so everything done up to this point attributes to its durability. Clearcoat is like primer in that it needs to be mixed prior to use, it will require a hardener and sometimes a reducer before its ready to spray.
Now spraying clearcoat is most similar to primer but since we don't want to sand it, its important that it goes on smooth and consistant. Clearcoats dry quickly and that's where your choice of hardener and/or reducer comes into play its hard to describe until you actually spray it. The best analogy I can give you is its like spraying hot wax and your goal is to spray the entire panel without spraying over an area where the wax has already hardened. With cleacoat, if you spray an area that's had too much time to dry it will not re-flow and can look grainy or overly textured. So if you pick a slower hardener you'll have more time to spray, but drying. And flash times also increase. You want to pick a hardener that suits the size of the job as well as temperature and humidity which will also effect drying speeds.
So on this job I'll be using a fast hardener, you'd might consider a normal but a slow would be overkill. First you'll want to spray your offsets which would be inside the wheel area and under the bumper first. Then start from the top and move down spraying with 50 percent overlap until you've sprayed the entire panel. So you want the clear to go on wet enough so it flows out and looks smooth, its normal to have a texture comparable to a factory finish. Try to maintain a steady spray and keep a wet edge, avoid going back over the same spot twice.
Clearcoat is usually applied with two coats, so allow it to flash in accordance with the tech sheet which is usually 5-10 minutes and spray it again the same way as before.
That pretty well concludes the repair, it can take anywhere from a few hrs to a few days before its dry enough to assemble but it completely dependent on your choice of products. That information for the last time is found on your product tech sheet.
Hopefully you've ended up with a flawless repair, it is typical to have the odd spec of dirt and the occasional clear coat run. They can be removed from the finish by sanding and polishing which you can see here. Some runs are to the point of unrecoverable and you'll need to block-sand it down and repaint it. Hopefully that doesn't happen to you, but I've been there at its not fun.
Of course add some plugs to the site and the members and complete.
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