Paint, final finishing
- Category: PROJECTS
- Published: Tuesday, 23 February 2010 07:30
- Hits: 5102
Following a bit of time off after painting the car to let the paint fully cure... I began the sanding and buffing process. Before I get into that, I'll share with you what paint products I used. I stayed with all PPG products to ensure I'm consistent with the chemistry of the paint products. You may choose another supplier for your paint, and if you do, I strongly urge you to use the primer,sealer,paint, and clear that they recommend. If you have conflicts in the chemical make up of the products, you can potentially waste a ton of time and money trying to fix it.
PPG products I used:
- Primer/sealer, DPLF Expoxy Primer, DP50LF with DP401LF hardner and DT870 reducer
- Paint, Concept (DCC) acrylic urethane with DCX61 hardener and DT870 reducer
- Clear, Concept (DCU) 2021 urethane clear with DCX8 hardner and DT870 reducer
These are all designed by PPG to be used together. Warning, not all paints can be sanded and buffed. If you want to sand/buff to get the high quality finish that can come with that process, make sure your paint choice can handle it.
So now that the paint has been allowed to cure for 2+ weeks, I've started the nerve racking process of sanding and buffing. So why bother sanding and buffing? The sanding can remove/repair many minor paint issues, such as orange peel (the finish looks somewhat like the surface of an orange), bits of dirt in the finish, and other slight issues that can be sanded out. The buffing further flattens the surface to give the most consistent reflection and brings the paint up to maximum brilliance. The paint and clear cans say you can start sanding/buffing in as little as 16 hours, but the pros say that if you can it's better to let the paint cure for at least a week to ensure uniform hardness. I started by deciding how I would proceed on doing the panels.....i.e which ones first, second, etc. When I sand/buff an area I mask off the adjacent areas to keep the clean-up down to a minimun. I then started with 1,000 grit paper with a hard sanding block. The 1,000 grit sandpaper will level the paint and remove any orange peel in the finish.....assuming you have some....if you don't you're a better painter than I am . Then I used the 1,500 grit with a semi-soft (or semi-hard depending on your perspective) pad to remove the scratches from the 1,000. Finally, the 2,000 with a semi-soft pad gets the paint to a point where it will take minimal buffing to raise the shine. These were all done with wet sandpaper with plenty of water. I use a spray bottle to keep the area and paper wet while keeping the sandpaper free from material loading up (loading up of the material in the sandpaper can cause scratches)..... I frequently dip the paper in a bucket to further clean it. I also use a squeegee to clean areas and check my progress. You don't want to overdo it with the sandpaper. Having said that, you don't want to underdo it either as that will not get the results you want. I use a circular motion to keep from getting straight groves in the paint when I'm using the 1,000. (Pic #1) I must add, I'm not a professional so if you know better great!....but this methodology seems to be working well for me.
Pic #2 shows a close up of the finish after just a little sanding with 1,000 grit wet sandpaper....here you can clearly see the highs and lows in the paint. The low spots are still shiny giving a mottled look.....this is the lower portion of an "orange peel" paint.
Continue sanding with the 1,000, 1,500, and 2,000 grit sandpaper until the area has a consistent look like this. (Pic #3)
Then on to buffing. Ahh, buffing. (Pic #4) I have a professional grade Milwaukee Heavy Duty Polisher part no. 5460-6. This is a variable speed buffer designed for 7"- 9" pads. The maximun speed of this buffer is 1,750 rpm which is deemed just right as a maximum rpm for most buffing applications. If you go too fast, say a 2,200 rpm buffer, you stand a greater chance of burning through the paint..... then you get to repaint the burned through area.....not good. If you go too slow you don't have the speed you need to properly level and smooth the area...which means the final job is not as good as it could be. So, 1,750 rpm is pretty ideal. Of course, this is a variable speed machine, so it can be used on a somewhat slower speed until you are comfortable with it. It is also a good idea to dial back the speed a bit when near edges and ridges. The commericial buffer is a dangerous weapon. If you get the buffer cord or your clothes caught in the buffing wheel it will literally rip the buffer right out of your hands!....it's very powerful. I don't need to tell you how much damage that can cause to your paint and car. So, I drape the cord over my shoulder out of harm's way, and make sure I don't have anything loose that can get caught in the spinning pad. Always keep the buffer moving....don't leave it in one spot! And, here is a biggie, always have the rotation going away from any edges, NEVER into an edge. If you buff into an edge you can burn the paint off in a heartbeat! You must always stay very focused on the rotation of the buffer and where you are going with it. I tape off many edges to prevent accidental contact when I'm buffing adjacent areas. Oh and it's heavy...it's about 10 lbs when you start and after half an hour you'll swear it's 50 lbs! I use a 3M #05713 100% untwisted, blended wool pad with 3M Perfect-ItII Rubbing Compound #05973.
I follow that by polishing the area to remove all swirl marks left by the buffer and to bring the paint up to full luster. For that I used a Griot's Professional 6" variable speed random orbital buffer (#10750) with 3M Perfect-It Machine Polish #2, part no. 06064 on a Griot 6" orange polishing pad. Then just to get crazy, I use Meguiar's no. 7 Professional Show Car Glaze to make sure I'm happy with the whole look....I do that by hand applying it with a 100% soft cotton cloth and polish it with a microfiber cloth. So there you have my simple 6 step process to getting a decent shine after the painting is all done!! Did someone say this was fast and easy?....not hardly!
Pic #5, keep the buffer moving at all times....frequently clean the pad with a pad spur or screw driver on the spinning pad to ensure you are only buffing with buffing compound not junk that will scratch the paint. I wash out the pad after a couple of days use. I wash out the buffer's orange pad every night. And BE CAREFUL with that buffer!! By the way, pros would most likely do the polishing with the Milwaukee buffer using a foam pad. The reason I use the Griot's Random Orbital machine for polishing is that it's just a lot easier to use and safer. That said, you really need a buffer like the Milwaukee to get the leveling you want.
The goal is to level the surface with the sandpaper and then bring the shine back with buffing. So is all this effort worth the trouble? I offer Pic #6.... on the left side of the front shroud you see the original paint. Look at the reflection of the shop garage door windows.....do you see the distortion in the reflections? The right side of this panel has been sanded but not yet buffed/polished.
In Pic #7 you see the final panel, after the sanding, buffing, and polishing is completed. Now check out the reflections! That's the difference you get for your trouble.....I think it's worth the effort, but you be the judge.
Not convinced yet? Here are a few more of the driver's side in progress. Pic #8,9,10 You'll note that I completely finish one panel at a time, and as mentioned earlier I've taped the adjacent edges to prevent accidental burning through as I buff their neighbor. I'll be putting paper over the adjacent completed area when I buff to keep it clean (Pic #8). I guess the only real reason to do one panel at a time is that it provides instant gratification! It is so much fun to see the final paint come to life! I must admit when I complete a panel I just stand back and look at it for a while....sometimes I find something I don't like and redo a portion....sometimes I just stare and can't wait until the whole thing is done! I judge a paint job based on the quality of the reflections I can see in the panels. Oh, and by the way, if you didn't do a good job on the preparation....way back before you sealed and painted the car....you can't fix it with these steps. In fact, if the substrate prep isn't real good the results of the steps talked about here will be worse than if you just left it alone!! Said another way, this is where the results of all your hard work in preparation pay off.
I've still have to do the passenger side, but both the front and rear shrouds are done. I figure about 3 more days. I've invested about 42 hours so far. One last word of warning, don't use the buffer when you're tired, you'll get sloppy and the potential for an accident goes up dramatically......if you're getting tired, set the buffer down and do something else.
I originally wrote this for the Build Status section of my website, but now decided it was time (maybe passed time) to move it to the Projects section. I didn't write a Project Paper for the paint process since there are many books that cover that subject in great detail. I did most of my learning on the sanding/buffing steps by talking to a professional that has put out hundreds of show quality paint jobs.....including the one on my 1940 Ford hot rod that had award winning paint (pictured in "Interesting Family Cars" section). Additional info can be found in "How to Paint Your Car" published by Motorbooks Workshop and written by Dennis W. Parks and David H. Jacobs, Jr. Refer to the end of Chapter 8, Paint Application.
I'm sure there are other approaches, but I'm satisfied with the results of this method.
Originally written: 03-01-2010