Ok, I have to ask this 1. I've heard, and read about orange peel on here. But, I'm not exactly sure what it looks like. The reason I'm asking is I'm trying to paint my car parts so I can put some of it back together. It's 68 Arctic White, and if I look close at it I can see what looks like a fine texture in the paint. It feels smooth, but I can still see it. I haven't put any clear coat on it yet. I have wet sanded it twice, and it looks better than it did but still there. Do I keep sanding it until it's gone? I don't want to take all the paint back off. I'm assuming it will still be there if I clear coat it, just under the clear. Sorry for my lack or knowledge on this subject, but I'll never know if I don't ask. Hopefully I don't get slammed toooo hard for it :Brow: Thanks Dan :3gears:
Listen, you can get a near orange peel job with "todays" paints. It really is no different than years ago, you are GOING to get a certain amount, PERIOD. I do want to make it perfectly clear, you DO NOT, EVER sand a base coat color prior to clear. There are a few brands that you could pull it off, but honestly, there is NO reason to do it. And more importantly, there are some brands that have a bold print warning in the tech sheets "Do not sand base color". So, read the tech sheets to find the proper info. Below are some basic tips for reducing orange peel. Brian >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Basics of Basics Atomization By Brian Martin Being HVLP and low VOC products are the way the industrys going I will be referring to them in this discussion on painting and paint guns. Most all basic issues dealing with HVLP can be applied to conventional guns, atomization is atomization. The HVLP just arrives at it differently. The object of the spray gun is to break up the primer/sealer/paint/clear (I will call this PSPC from here out) into small particles and lay them in neat little rows on the panel being PSPRed. So the whole outcome rests on how well the gun is doing this. Picture the droplets of PSPC coming out of the fluid tip of the gun and then the air slapping them into smaller droplets. You have two things that help you with this process, air and solvent. Solvent can mean something that is already in the PSPR from the manufacture or something the manufacture has told you to add to it. By the way, you should always mix in proper ratios as instructed in the tech sheet. The thinner (less viscosity) you get the PSPR or the more air you have at the fluid tip of the gun the more it will break up the PSPR. The target for you is getting the perfect balance needed. Too much solvent and the PSPR will have no body, fill, durability, etc. Too much air and you blow the PSPR everywhere but the car, poor adhesion, excessive texture, etc. So, the answer is proper air supply and gun (and fluid tip) choice and how you adjust it. With todays high solids-low VOC (Volatile Organic Compound, you know the bad stuff that goes up into the air we breathe) products there is less solvent. And with HVLP guns there is less air at the cap to break up the PSPC, proper air supply and gun setup is more important than ever. FIRST THINGS FIRST, your compressor and air supply. An HVLP gun requires more VOLUME of air to operate (the V in HVLP, High Volume Low Pressure). Now you may notice that your HVLP gun is adjusted at maybe the same PSI as an old conventional gun, around 50 lbs at the gun (many HVLP guns are set at much lower though) so where is the Low in PSI they are talking about? It is at the actual air cap where the air and paint come out. An HVLP gun has only 10 lbs at the cap while a conventional has upwards of 50! This 10 lbs at the cap is something you have no way to measure. AT THE CAP means at the fluid/air cap where the paint sprays out. It takes a special air cap with a gauge on it. This test cap is used by paint reps, air quality control agents but only a few painters. I have never seen on in a body shop. I say this because the instructions that come with many HVLP guns tell you to adjust to 10 lbs at the cap all the while they give you no way of measuring the cap pressure. There is usually a MAX PRESSURE stamped on the gun or in the instructions. This max pressure is the maximum pressure you can set the gun pressure and still keep the cap pressure at the 10 lbs max at the cap the law allows (in most VOC regulated areas where HVLP is required). So the VOLUME of air (CFM, Cubic Feet per Minute) is the key to proper atomization with an HVLP. If you have a gun that requires 15 CFM you will need a compressor and plumbing that will produce that at a very minimum. There are HVLP guns that need as little as 7.5 CFM so you can get good results even from a smaller compressor. Air supply is a complete subject by its self so lets assume that you have the air supply needed and move on to gun set up. So atomization is the key, but why? Why cant you just lay it out wet and let it flow, as an old painter will say. Picture a jar full of bbs, they will represent well small, atomized droplets of PSPC. The gaps in between the bbs is solvent. Now picture a jar filled with marbles, they will represent large, poorly atomized droplets of PSPC. The gaps in between are, you guessed it, solvent. If you apply your PSPC in large poorly atomized droplets, what you will have is a film full of solvent. This can and will cause slow curing, shrinkage and dieback (the loss of gloss in the hours and days after application). So, now that we have learned the need for gun set up, how do we do it? Lets start with the fluid tip choice. The newer high solids low VOC PSPC products need to be broken up more, so a smaller fluid tip is needed. Basically you want the smallest fluid tip that will still allow you to PSPC the particular part you are PSPCing keeping the entire thing wet and in a fair amount of time. In other words a 1.0 tip would be beautiful for clearing one fender, but would be lousy to paint a complete. The application would be way to slow and the first panel would be way to flashed by the time you got around back to it. So you need to compromise, a 1.3 is a great all around tip, while a 1.5 though getting a little big, can get you by. If you read the tech sheet on the particular product you are shooting, it will have a recommendation for fluid tip size. There are needs for other tips, for instance when shooting polyester primer you may need as big as a 2.3, but for many urethanes and epoxies, or base coats the 1.3 or 1.5 will work great. If you plan on using a pressure pot or paint a bus, all bets are off and we would need to study a little bit more. As an example of the use of a 1.3 tip I did a test once that proved the point well. I shot two panels of metal with a med solids urethane primer. One was shot with a 1.3 super high atomizing top of the line topcoat gun. The other was shot with a 1.5 (or a 1.7 I cant remember) hoser primer gun. Three coats were applied and after a full cure (the one shot with the larger gun took MUCH longer to flash and cure by the way) the film thickness was measured. The one shot with the 1.3 tip was 2 tenths of a MIL thicker! The larger gun laid out the marble sized droplets full of solvent and when the solvent flashed the film shrank. This however doesnt mean I recommend a 1.3 tip for your primer gun. It is only meant to make the subject of atomization easier to understand. Always refer to the tech sheets of the particular product you are shooting to see what tip you should be using. Air supply is a subject that could fill many pages by its self. So we are going to assume you have that covered and move on to gun set up. You need to tune your gun EVERY TIME you use it just as you would tune a guitar before you perform. This is done with a very basic spray out pattern test. This very basic test tells you how your gun is atomizing and you adjust it to achieve the best atomization you can. Lets do a spray pattern test: Set the fan width as need (you dont want to change it after you have tuned the gun). Turn out the material knob about 2 turns. This is the mixture adjustment, kind of like the idle screw on a carburetor. The farther in it is screwed the lower the fluid to air ratio is and the smaller the droplets will be. The farther out it is, the higher the fluid to air ratio is and the larger the droplets. Set the air pressure at the inlet to the gun to the manufactures specs. On an HVLP gun this spec is usually found on the gun and is the maximum PSI it can have while still maintaining the maximum 10 lb at the cap for legal HVLP transfer efficiency (68 %). You are now ready to do a test spray out. Tape a piece of masking paper on the wall for the test. Hold the gun at a right angle to the wall, just as if you were going the wall. Hold the gun at a spread out hands distance (about 8 or 22cm). Pull the trigger to completely open for a split second and then close it. You want an ON-OFF wide open-completely closed in ONE movement. You should have a cigar shaped pattern with complete coverage in the center with fading coverage going away from the full coverage cigar shape in the center. The center should be fully covered without any runs. If you have runs, either you are holding the trigger too long, you are too close or the gun is simply applying too much material. In which case you need to screw in the material knob or turn the air pressure down. But most likely if you have turned the material knob out the 2 turns and the air is set at the factory specs, you are just too close or holding the trigger open too long. The droplets you see trailing off the center are what you will use to tune your gun. Turn in the material knob to make the droplets smaller (and or raise the air pressure). The balance you need to attain is the smallest droplet size possible before you loose the coverage desired. In other words if you turn in the material knob too far, not enough material will be coming out to cover the panel! That balance of atomization and enough material coming out is what you are after. Now, youll notice that I said, raise the pressure to the gun, while earlier I said to set it to manufactures specs. This can be anywhere from 25 lbs to 50 lbs. This gun manufactures recommended pressure is AT THE GUN. This means at the INLET of the gun, NOT at the cap and NOT at the other end of the hose, but AT THE GUN. If your gun doesnt have a regulator on it, then install one. This regulator will tell you at all times what the pressure is AT THE GUN, which is what you need to know. Be sure to buy a quality regulator from a paint gun manufacture. Some cheapie regulators are going to rob air volume from your gun because of restrictions within them. This is something most home hobbyist CAN NOT afford do to small compressors. If you dont have the air volume to atomize your paint, you are NOT going to get satisfactory results. We are talking a very small adjustment. It is a fine balance in material to air ratio and a little more air than specified is okay. Even if it is an HVLP gun the inlet pressure recommended is to maintain the 10 lb limit at the cap. Well, about three quarters of the country has no regulations for HVLP use so if you go over the 10 lbs all it will do is atomize the material a little better. You may loose a little of the benefits of HVLP though. But remember you have a lot of control with the material adjustment knob. After you are happy with the droplet size, DONT TOUCH THE FAN CONTROL. It will change the PSI at the cap and will change the atomization you worked hard to get. Do this spray out every time you spray as material change, temp, and humidity will necessitate a spray out droplet pattern test. Good luck!
You can find orange peel just about anywhere. Almost all factory done cars come with free orange peel. Even some of the most expensive cars come with it free. Its sort of sad once you learn what a real paint job looks like. You pay $40,000 for a car with a $200 paint job.
Ok, I have determined from the above posts that I do have orange peel on the fender. I have sanded it down twice ( before reading th post telling me not to ), and it's still there. Do I continue to sand it down until it's gone, then repaint the fender? Or is there another way to remove it. I only painted 1 fender at a time for this reason. Now I only have 1 fender to fix. I painted the other yesterday afternoon, and it turned out much better. I made a few adjustments to the gun, as mentioned in the earlier post. I'm much happier with that 1. Now how to fix the first 1. Thanks, Dan :3gears:
You may not want to hear this: Do Over !!!! Not the most popular response but if you are not satisfied with the results now then you will most likely end up doing again anyway. Break out the sander!
That doesn't bother me too bad. I agree with you that if I'm not happy with it now, I never will be. That's why I did 1 fender at a time. I'll chalk this 1 up to a rookie error. At least I don't have to re-do the whole car. I have plenty of paint to repaint it anyway. Thanks for the reply. Dan :3gears:
Dan, Is this your first attempt at painting a whole car? If it is then I suggest you do a search for posts by MARTINSR. Brian is a very talented and experienced bodyman and painter. Lots of great info is offered by him. If you don't find too much on this board you can check over on Buick.net Good luck and don't get discouraged. :beer
How far down should I sand the fender. Do I need to completely start over? Or just remove enough paint to get rid of the orange peel. Thanks, Dan :3gears:
If you can eliminate the orange peel without stripping it completely then that will be fine. Then reshoot and hope for the best.
