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Thread: Clearcoat sanding technique for mirror finish

  1. #1

    Default Clearcoat sanding technique for mirror finish

    Hello everyone!

    Nice to join what seems like an excellent site and forum! I look forward to getting involved!

    I've been practising orange peel sanding technique on scrap panels and ran into a problem; I can remove all the texture, but then I'm still left with little waves in the finish afterwards that make it look like some minor orange peel is still there when looking up close.

    This has plagued me for a while now. However, I was only using 1200 grit maximum back then and it's only recently I found that if you want the flattest possible finish you should hand sand. It also wasn't until I discovered this site I realised that using as low as 400g might be necessary, by hand.

    What grit should I be using to level, below 1200? Should I be using the longest block possible when I can, or can flattening work with a small block?

    What is the correct method to follow when going for the flattest, most even, mirror finish possible? What grits, what dry, what wet? One issue I have with wetsanding is my sandpaper always catches on some strokes and I don't know how to solve it. It will grab on, like suction, and cause me to put gouges in it no doubt. To clarify, this is all on OEM paint so far.
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    Last edited by lmeddick; 07-24-2017 at 01:02 AM.

  2. #2
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    Yes, blocking it with a more coarse grit can help level the orange peel but you want to be careful to have enough clear so that you don't sand through the clear.

    Start by using a "good" spray gun that will lay the paint on smooth. Many low-end guns will produce a lot more texture and make a smooth finish much harder to achieve.

    Also make sure that you apply enough clear so that you don't risk sanding through to your base coat. If you do sand through the clear you will probably need to apply more color before re-clearing and that can also cause problems.

    We very rarely sand our clear with dry paper. Using a Sagola spray gun we have almost no orange peel and if we sand we will normally start with 1500 wet by hand to start then 2500 by hand or 3000 on an orbital sander. Sometimes we'll even go to 5000 on an orbital in order to minimize buffing time. Dry sandpaper can pick up particles that can put deep scratches in the paint and they can be difficult to remove but wet paper has less tendency to cause scratches because contaminants are flushed away.

    Another good method of achieving a mirror finish is to level the peel with sandpaper then re-apply more clear (a "flow coat") with over-reduced clear then sand and polish. This is what many show car painters do.

    If you're wet sanding you should have a clean squeegee so that you can remove the water in order to SEE your progress. Usually a 12" block is long enough but you may also need rounded blocks in order to address some of the surface shapes.



  3. #3

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    Thanks. I wondered what a flowcoat was. I'm sure I'll find out on the DVD but what's a 'wet coat'?

    Ahh I see where you've posted in another thread a while ago that starting with a fine grit has a tendency to leave waves in the surface while a more coase grit would tend to flatten it. Sounds like my initial problem is resolved now! I'll polish out during the week and find out.

    Any thoughts as to why my sandpaper gets caught when wetsanding? Perhaps I'm not soaking it long enough. Recently I've just been wetting it with no soak time. My sandpaper occasionally grips more during certain strokes and when using a long block I find myself gouging it.
    Last edited by lmeddick; 07-24-2017 at 03:56 AM.

  4. #4
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    Quote Originally Posted by lmeddick View Post
    Thanks. I wondered what a flowcoat was. I'm sure I'll find out on the DVD but what's a 'wet coat'?

    Ahh I see where you've posted in another thread a while ago that starting with a fine grit has a tendency to leave waves in the surface while a more coase grit would tend to flatten it. Sounds like my initial problem is resolved now! I'll polish out during the week and find out.

    Any thoughts as to why my sandpaper gets caught when wetsanding? Perhaps I'm not soaking it long enough. Recently I've just been wetting it with no soak time. My sandpaper occasionally grips more during certain strokes and when using a long block I find myself gouging it.
    I doubt that soaking will make much difference in the amount of drag on the paper but it should be soaked for about 15 minutes before using. What makes a bigger difference in the amount of drag is the amount of water used while sanding. We usually use a pump sprayer to continually wet the surface while we sand then we use that squeegee to remove the water and check out progress.

  5. #5

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    Quote Originally Posted by Len View Post
    I doubt that soaking will make much difference in the amount of drag on the paper but it should be soaked for about 15 minutes before using. What makes a bigger difference in the amount of drag is the amount of water used while sanding. We usually use a pump sprayer to continually wet the surface while we sand then we use that squeegee to remove the water and check out progress.
    I've been using a sprayer but admittedly I've been trying not to 'over saturate'. I'll try using more water tonight. I have a squeegee to use. Can I use 400,600,800 and 1000 wet on the clear? I'm just not sure what dictates whether you sand wet or dry.

  6. #6
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    Quote Originally Posted by lmeddick View Post
    I've been using a sprayer but admittedly I've been trying not to 'over saturate'. I'll try using more water tonight. I have a squeegee to use. Can I use 400,600,800 and 1000 wet on the clear? I'm just not sure what dictates whether you sand wet or dry.
    The problem with using a coarse grit is that it can be difficult to see when you've eliminated the coarse scratch when you sand with a finer grit. As long as the coarse scratch is sanded out then it's ok to use coarse paper.


  7. #7

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    Quote Originally Posted by Len View Post
    The problem with using a coarse grit is that it can be difficult to see when you've eliminated the coarse scratch when you sand with a finer grit. As long as the coarse scratch is sanded out then it's ok to use coarse paper.

    My concern is whether it's okay to use the coarser grits wet? Will it diminish the flattening ability?

  8. #8
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    if it were me, i'd start a bit more conservatively. maybe 800 on a fairly hard block to start. i've been working on one of my projects, trying to get rid of some waves, and i'm having pretty good luck with 1200 on a hard wooden block. my surface isn't nearly as irregular as yours though, but it still takes a good amount of sanding to do the trick. make sure to wrap the paper tightly, and not too much pressure, so you cut the tops off of the waves.
    b marler

  9. #9
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    Quote Originally Posted by lmeddick View Post
    My concern is whether it's okay to use the coarser grits wet? Will it diminish the flattening ability?
    Wet paper tends to cut better/faster than dry paper and can also leave a deeper scratch. Wet sanding will work better for removing waves or orange peel when the correct block is used.

  10. #10

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    Quote Originally Posted by bmarler View Post
    if it were me, i'd start a bit more conservatively. maybe 800 on a fairly hard block to start.
    Quote Originally Posted by Len View Post
    Wet paper tends to cut better/faster than dry paper and can also leave a deeper scratch. Wet sanding will work better for removing waves or orange peel when the correct block is used.
    That's so much to you both. You know, all this time I had the misconception that dry cut more! Wow I'm so surprised!

    I'll have to watch the pressure also - I tend to press firmly, assuming that would be best for levelling.

    Correct block will be hard like Balsa right?

  11. #11
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    Quote Originally Posted by lmeddick View Post
    That's so much to you both. You know, all this time I had the misconception that dry cut more! Wow I'm so surprised!

    I'll have to watch the pressure also - I tend to press firmly, assuming that would be best for levelling.

    Correct block will be hard like Balsa right?
    Yes, hard balsa will work, personally I like the DuraBlocks.

  12. #12
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    i have dura blocks too, and they work pretty good. but i also use a hardwood stick and even an aluminum bar. the dura blocks didn't level the surface for me on the first cut so i use the harder blocks first. maybe if i used coarser paper for the first cut the dura blocks would be fine. i'm just nervous to burn through, so i use 1200 for the first pass. don't get me wrong, the dura blocks remove any peel or small defects, but when i sight down the panel at an angle i still see those pesky waves. the hard blocks help me remove those.
    b marler

  13. #13
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    Quote Originally Posted by bmarler View Post
    i have dura blocks too, and they work pretty good. but i also use a hardwood stick and even an aluminum bar. the dura blocks didn't level the surface for me on the first cut so i use the harder blocks first. maybe if i used coarser paper for the first cut the dura blocks would be fine. i'm just nervous to burn through, so i use 1200 for the first pass. don't get me wrong, the dura blocks remove any peel or small defects, but when i sight down the panel at an angle i still see those pesky waves. the hard blocks help me remove those.
    I never get "waves", what do you think is causing them? I got orange peel before I used my Sagola but not waves.

  14. #14

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    Quote Originally Posted by bmarler View Post
    i have dura blocks too, and they work pretty good. but i also use a hardwood stick and even an aluminum bar. the dura blocks didn't level the surface for me on the first cut so i use the harder blocks first. maybe if i used coarser paper for the first cut the dura blocks would be fine. i'm just nervous to burn through, so i use 1200 for the first pass. don't get me wrong, the dura blocks remove any peel or small defects, but when i sight down the panel at an angle i still see those pesky waves. the hard blocks help me remove those.
    I got a balsa wood block today alongside two aluminium blocks myself. I like the way the aluminium feels but the negative is small blocks being required because they don't flex at all obviously.

    Quote Originally Posted by Len View Post
    I never get "waves", what do you think is causing them? I got orange peel before I used my Sagola but not waves.
    I was under the impression they're caused by uneven sanding. I've had them in every single OEM painted panel (never worked on custom painted) I've sanded and because I noticed after sanding, I thought I'd inflicted. I'm starting to question that though because if so why would they be so hard to remove and be consistent? Surely anything that is causing a wavey appearance is beyond what you could inflict? When it really shows up is when all the orange peel is removed. The panels end up looking like they have minor peel upon inspection even though you know it's gone. Thing is, who knows whether they were there already before the peel went or not, because you won't see them with peel and theyre obvious afterwards, so maybe they were just there all along but the peel hid them? Or perhaps it's just all peel but the last bit. This is an example - look at the light, the outlines are distorted on what ragtop clearly showed was otherwise a completely flat paint job * this image is 68ragtops*

    IMG_4759.jpg
    Last edited by lmeddick; 07-25-2017 at 02:59 PM.

  15. #15

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    Quote Originally Posted by Len View Post
    I never get "waves", what do you think is causing them? I got orange peel before I used my Sagola but not waves.
    Seeing as it's alien to me at the moment, if you spray and get no peel ANYWHERE and you're doing a show car, does that mean assuming no runs etc that the finish is show ready without any sanding?

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