Sanding UV clear

W

Whiskyb

I am back on my feet and ready to start sanding. Last Saturday I was able to spray 2 good coats of UV clear. Minor peel and very little trash. Going to start with 800 wet today. Does the peel need to be completely eliminated or just knocked down?

I was not sure if this weekends 3 coats would fill minor imperfections or accentuate them.

Cheers,:D
 
As long as there is enough build, all the way flat is best, as Bob says. Just tread lightly if you run into any dry-ish spots which will be revealed by the very fine texture of the orange peel. I'm sure you are fine but sanding through is a bummer to be avoided.
 
Isn't 800 a little fine for the thane wave if he is re-clearing? I guess there would be that much with only two coats?
 
It's easier to recommend a coarser grit if more coats have been used. Pretty hard to see the job from where I am sitting. But you are right, a coarser grit would make it flatter.
 
yeah, a picture would be worth a thousand words, two thin slick coats of clear vs. two heavy anatomized coats of clear could vary greatly in thickness. From the description it sounds like there's just a little trash and some minor peel so I would guess the coats are thin-making 800 grit a good choice for less chance of cutting into the base. 800 will cut out even the worst of thane wave if the right blocks are used but it does take more time. If a soft block is used a coarser grit is needed or the block will just ride the wave-JMO
 
The two flat panels (hood and roof) I started with 600. The rest of the car being so curvy I have been using 800. Takes a little longer with the 800 but I am afraid to go through. Plan is for new plastic in the booth as the old stuff was really reducing my lighting. I have added a few more low 4'ers as well. Saturday morning I plan on 3 good heavy coats. I have been doing lots of reading on here and believe my technique was too fast. I am going to try slowing down and laying her on
 
sometimes i believe i am a sculpture as well as a painter too... uvc is great for that!
 
I have a related question. When sanding with lower grits like 220 and working upward is there a standard or recommendation in how big of a jump in grit size to make?
My thoughts were 500 grit increments seem to be pretty safe but is that just for 1000 and above? Should the lower grits be made in 100 grit increments or 200? Normally I would go from 220 to 400 or even 600 without much thought.
 
Just so nobody misinterprets the last post-do not sand clear with 220 grit I understand the question with the reference to 220 to be for undercoats/primer surfacers and fillers?
There's no rule or guidelines set in stone that I follow. On small to medium repairs I'll often break and rough in filler with 80 stopping short of perfect contour then switch to 180, then sometimes apply guidecoat and finish it off with 320. Polyester primer I have started with 80, guidecoated then switched to 150 or 180 or 220, applied guidecoat again and sanded again at 320 or 400-all depends if the shape is right and enough build is left. Urethane surfacers I'll start with 180 or 220 on big jobs and sometimes 320 or 400 on smaller jobs and sometimes apply guidecoat and finish with 600-same with epoxy. Think of it this way:if your contour is right at 80 grit you should have no problem resanding with a finer grit to the bottom of those 80 grit scratches while still maintaining the right shape. Grits I keep on hand: 36,80,120,150,180,220,320,400,600,800,1000,1200,1500,2000,2500,3000 and some get used more than others but they all have their own purpose. Another thing to think about when colorsanding: If you're using a good flat block or high density contour pad and removing minor orange peel (not urethane wave) you can stop sanding with the coarser grits before all the peel is out and still maintain straightness. If there's a trace of shiny specks left showing the peel hasn't been completely cut out but say 90% that's OK, use them shiny spots as an indicator of when to stop with the next finer grit and it'll also leave more clear on the car.
 
Thanks Bob,
I didn't mean to throw a curve ball and was by no means suggesting sanding clear with 220. I was recently told that when going through the lower grits you should only go in increments of 100 and I disagree with that. I can't see the sense in going 320 to 400 to 500 all the way to 800 grit. It just seems like a lot of extra sanding to me. I figure 220 to 320 or even 400 is acceptable and then to 600 and so forth. Once I hit a 1000 then it goes by 500 increments.
Does this sound reasonable?
I keep pretty much the same grits you have on hand.
 
A rule of thumb that works OK is to double the number when switching coarser grits, (40,80,150) but when you get toward the color sanding grits you only go half again or so (800, 1200, 2000, 3000). There is room for disagreement here, eventually it becomes whatever works for the individual. But the above is a good starting point.
 
I find it harder to work the scratches out when i jump too much on the grits for color sanding. I start with 800 then follow with 1000, 1200, 1500, 2000, 2500 then trizact 3000.

Lately i've skipped the 1500/2000/2500 stage by hand and used 1500 on a da with a soft pad, then finished with 3000. Seems to be a lot easier for me. Still have to finish out all the concave and small areas with atleast 2000 though, as you cant get those areas with a da. I've rreplaced 3 different sanding stages with one da stage...time saver.

The da finish just seems much nicer....but it is still necessary to do the initial block with 800 (or coarser if thats what you desire).
 
there is a reason they make all the grits of paper. each one is designed to remove the scratches of the lower grit. jumping grits just makes more work and leads to scratches left behind. especially in clear. jmho but i will use each step as it goes faster that way.
 
no kiddin. I found myself spending more time on the buffing wheel and using a lot of compound when trying to jump grits thinking it would go faster. I would rather buff than sand, but the finish is so much better and easier to buff if you step up your grits the correct way. Using the 3m compound, it takes very little compound and very low speed to buff out. I hate the sanding part but has to be done!
 
Thanks guys.
Shine, do you use each step in the lower grits like 320-400-500-600 or are you just referring to the higher grits when sanding your clear?
 
i never sand primer further than 320 . i use 600 to block for reclear . i use 800-1000-1200-1500-2000-2500-3000 on cut and buff. i do it because i don't want start polishing and see scratches that are still there. it only takes once to burn enough man hours to pay for all the sandpaper.
 
Same here. When you consider material vs labor, sandpaper is fairly cheap. I've seen guys penny pinch on the sand paper...watch high end shops do the same and the quality suffers. You dont want to waste...but at the same time you dont want to work yourself to death and waste TIME. Time is money. This pertains to all areas in paint and body...not just the cut/buff process.
 
So sanding primer to 320 will not cause scratches to be seen in your base??? Or are you applying a sealer coat of epoxy to over the 320 sanded primer and letting that fill the scratches?
Sorry for bugging you on this but I want to understand since I have been told primer needs to be sanded with 400 for solids and 600 for metallics.
 
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