How much wetsanding needed?

Discuss anything after that final masking comes off.



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PostPosted: Sun Nov 12, 2017 7:58 pm
This is my first time spraying a car, so bear with me if this is a newbie question. I put three medium wet coats of clear on and have significant orange peel due to my compressor's smallish (25 gallon, 6 scfm@90psi) size.

I chose a panel and got to work wetsanding. Started with 1000 grit, then onto 1200, 1500 and 2000. I then chose a subsection to test and used my Griots polisher and orange correcting pad with Meguir's ultra cut compound, and after 10 minutes could see that things weren't working the way I'd hoped. I just wasn't getting things smooth.

This is what the panel looks like after wetsanding, aside from the section I tried polishing-- the image is zoomable if you click it.
Image



After polishing that section I went back to 1200 grit and really took my time. The section in the red rectangle is where I am with it now:

Image


Am I correct in assuming that photo #1 isn't nearly sanded enough, and that photo #2, with the all-over 'haze', is more where I want to be? (I hope the photos are clear enough to show where things stand; I can try to take other ones when the light is better.)

I went easy on the wetsanding because I didn't want to burn through the clear, but I guess that's not likely to be a problem at the moment, that my bigger issue is flattening everything out?

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PostPosted: Sun Nov 12, 2017 11:18 pm
You still have orange peel in both photos.
Check this thread on page 11: viewtopic.php?f=12&t=22145&start=100

A rotary buffer is the way to go IMHO.
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PostPosted: Mon Nov 13, 2017 2:15 am
'68 Coronet R/T wrote:You still have orange peel in both photos.
Check this thread on page 11: viewtopic.php?f=12&t=22145&start=100

A rotary buffer is the way to go IMHO.


Thanks for the link, you did a great job there. May I ask how difficult it is to sand through three coats of (Summit Racing in my case) clear with 1000 grit, assuming you're smart about it; not too much pressure, keep the panel wet and clean, etc? I ask because I'd like to knock this down as quickly as possible. If I should stay with 1200 grit to play it safe then ok.

There's no way I can duplicate your efforts however. For me, this is my daily driver I'm painting, so 'good enough' will have to suffice. I know that a rotary buffer would be a step up from my DA unit, but if it's just a matter of spending more time with the DA (and less risk of burning through the clear) to get good results then I can live with that-- I just won't use the rotary buffer often enough.

It's just that right now there's so much peel that I have to take more action.



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PostPosted: Mon Nov 13, 2017 7:33 am
That's some pretty rough peel there. I have no experience with the clear you are using, but my guess is there won't be much clear left when you get all the peel off. UV protection could be compromised which can result in premature failure.

Have you though about sanding most the peel off, take a red scotch brite to it, then shooting a couple more coats of clear? You should be able to get it to lay down fairly well with a small compressor if you do one panel at a time and then let the compressor pump up. Or borrow a larger compressor?

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PostPosted: Mon Nov 13, 2017 9:42 am
When looking at your panel keep in mind that the shiny spots are the lowest level of the clear coat.
You have basically been sanding off the peaks of the orange peel and the valleys are still untouched.

I think BeoBob's suggestion is the best in this case. Get it as flat as you dare with the 1000 grit. If you use the wooden block like I did and sand just till it removes the shiny spots you "should" be okay.

When you spray your next coat of clear try moving the gun closer to the panel. If you were at 6" then move to 4" away and apply the clear "wet" not medium. It will flow out much better over sanded clear than it does over base. The trick is getting it to go on wet without runs but IMO better to have a minor run than a ton of orange peel.
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PostPosted: Mon Nov 13, 2017 11:29 am
Thanks for the advice gentlemen. I'll go with 1000 or 1200, get it as 'flat' as I dare, smooth with 1500 and 2000 and if buffing it works then great, otherwise I'll try another coat, using the techniques you mentioned to minimize peel.

I'm not overly concerned about losing UV protection in this case because I shot over single stage and so the paint itself has protection in it-- the reason for doing single stage plus clear is that I knew I'd have orange peel in the paint regardless, and my understanding is I can't wetsand and buff single stage metallic without affecting the look of the paint and orientation of the flakes and basically ruining things.

That reason, and with two layers of paint protection (SSU + clear) it protects me all the more from bird droppings, etc. That's the theory at least. This isn't a show car and my goal is a good shine without peel, and if I don't end up with a mirror finish (and I won't) I can live with it.

One question I did have was, how much surface area can I wetsand with, say, a 5x10" piece of 1200 grit before it loses its effectiveness? Approximately how many sheets of that size would I need for a compact sedan?



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PostPosted: Mon Nov 13, 2017 1:32 pm
larryq wrote:Thanks for the advice gentlemen. I'll go with 1000 or 1200, get it as 'flat' as I dare, smooth with 1500 and 2000 and if buffing it works then great, otherwise I'll try another coat, using the techniques you mentioned to minimize peel.



with what ya have, heres how id sand:
start with 1000 grit with a backer/block. sand in one direction like //////////.
get it all so theres no( or very few_ shiney spots.
switch to 1200 with a blacker/block and change direction to \\\\\\\\\\\\\.
then to 1500 and change direction to ///////////////////////
sand, squeegee off an area to check progress. proceed.
changing that direction helps see the refinement of each grit. when i start with 1000 in a ///// direction then switch to 1200 in a \\\\\\\ direction, if i still see scratches in ///// direction, i still have more sanding to do with the 1200.
good lighting helps to see the progress,too.

NOTE:
im not one of these guys that can rock out wet sanding, so i run some tape along body lines and edges i could sand through.
which was learned by sanding through when i was a REAL greenhorn. :)

P.S.
i hope youre not trying or thinking you can get the surface smooth with the compounds- get rid of OP with them.

P.P.S.
on this:
"One question I did have was, how much surface area can I wetsand with, say, a 5x10" piece of 1200 grit before it loses its effectiveness? Approximately how many sheets of that size would I need for a compact sedan?"

that depends on the quality of paper being used. using meguiars unigrit, ill change paper after a fender/door of regular size. as in, not a semi door or fender.
that doesnt mean the paper is shot and not able to cut any more. i just prefer to do that.

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