Urethane Wave?

DanMcG

DanMcG

Promoted Users
Is that what I'm looking at here. I hear about wave all the time but never seen a pic of it. This is low angle pic of a door I'm experimenting/ learning on. I sanded 1000-3000 (by hand and da) then cut with 3D 500. The lines you see are the power lines across the road.
This is a single stage Motocryl, white.
What say you, wave or something much deeper?
wave.JPG
 
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A good test to know if its urethane wave or primer that's not blocked flat enough is to block your primer to 400, then wipe with wax/grease remover and check for ripples before sealer/paint. If there are no ripples then but ripples after cutting and buffing then you know you didn't block the paint flat enough. Be aware that concave areas like that will greatly magnify any ripples/wave/texture or sanding scratch patterns that aren't fully blocked out by the next smoother grit sanding session.

What are you blocking the body with- both block type and grits used?

Same question for the paint- what blocks with which grits were used?

Blocking with soft-faced blocks will make it nearly impossible to get it 100% flat, especially if starting with 1000 grit on clear/ss.


If that's a test panel you may want to block it with 500 on an acrylic block to get it flat (check the reflection with w&g remover) and shoot 4-5 medium build coats of clear so you can practice blocking the paint flat with courser paper.



This is poly blocked with 80, 150, 220 with acrylic blocks, then sanded with 400 with a soft sanding pad. Guide coat was used between each step to make sure all of the previous grit scratches were sanded out. Even at super steep angles there are barely any ripples. To get the same look with paint you need to initially block the paint with hard faced acrylic blocks and course paper to eliminate texture and wave.

 
theastronaut said:
Blocking with soft-faced blocks will make it nearly impossible to get it 100% flat, especially if starting with 1000 grit on clear/ss.
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Well I guess that explains it, I did most of the paint sanding with a soft block starting with 1000 and 1500, then went to da and soft block with 2000, 2500 and 3000.
Thanks for the info John, I have a couple fenders to paint today so i'll be using you W&D method to check what I have before shooting them.
I never figured my first attempt at a paint job would be awesome so I'm not surprised at the outcome, but man is a little disheartening to say the least.
 
The big question??
Was there the so-called urethane wave before you buffed?
How straight was it after the paint was applied?
If it looked good then, then the sanding of the paint was wrong, and you put the unevenness in.
 
I thought it looked great thru the whole process, but I probably never looked at it from that low of an angle until now. From here on out I'll be looking for it as I go.
 
DanMcG said:
Well I guess that explains it, I did most of the paint sanding with a soft block starting with 1000 and 1500, then went to da and soft block with 2000, 2500 and 3000.
Thanks for the info John, I have a couple fenders to paint today so i'll be using you W&D method to check what I have before shooting them.
I never figured my first attempt at a paint job would be awesome so I'm not surprised at the outcome, but man is a little disheartening to say the least.
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If you never had experiences like these you’d never learn anything. That’s why the pro’s are pro’s; not because they’re paid but because they’re experienced, and experience is something you can’t learn anywhere.

I think you’ve got some redemption since it’s single stage; you don’t have a clear to risk burning through. How many coats did you apply initially? Since this is a practice panel, you could flatten that with 1000 with your Black Diamond blocks, give yourself a flat substrate to start with, and then shoot a few more coats and then cut and buff.

Or you could just try finishing out with sanding after your 1000 if you think there’s enough mil build.

I’d be curious to know from those more experienced if it would actually require 600 to level that.
 
im with shine and don. cant beat yourself up over it too much. especially if u plan on driving the car. hell you can even have it on a trailer and a rock chip in the middle of the door from a passing 18 wheeler and all the time you spent chasing perfect , gone...

hang it verticle and see how it looks. i bet it looks better....

hack disclaimer
 
Thanks guys, I'm done with it for now except trying out some foam pads and 3d 520.
For what it's worth, the 2 fenders that had 2 coat of SS from last year were sanded down with 800 and no sign of waves, so it makes me think I screwed up the door this week with the soft pad. live and learn.
Guess I need to find some 1000 sheet paper, any favorites out there?
 
My personal truck is an '86 GMC shortie, I'm dreading redoing the bad paint I bought it with, since it's hard for me to put that kind of time into my own stuff. One thing I do is make a custom block for rigs with long concaves, you can actually use the concave portion of the vehicle as a form to create a block with a rounded shape. The last one I did I just made out of an old block and plastic filler and then tweaked its shape and smoothed it with another block. They seem to work fairly well, you just have to make their radius very slightly sharper than the vehicle radius to keep the edges from digging in. Good complement to a flat block for these shapes, imo.
 
How long a block would you build? and you'd run it in a straight line front to back?
Thanks for the idea.
 
I have only made 9 1/2" blocks this way, since they are used in conjunction with much longer blocks. The radiused block is just for use inside the radius, to smooth away any block cut marks from sanding with the long blocks. Typically I will use a steeper X-angle when using the radius block, since it's trying to straighten mostly in the z-axis instead of the x-axis. In my eye, it's waves in the z-axis that plague concave surfaces. That's just my opinion, though. YMMV.

P.S. I also use the radiused block to do the initial and maybe 2nd color-sanding cut in the radius.
 
Again thanks for the help everyone, I'm starting to figure out the color sanding part. here's the other door sanded to 3000 with block up to 2500.
3000 door.JPG

I thought I did good until I moved it away from the indirect light and into a darker corner of the garage then I noticed I can see sand scratches from maybe 1000 or 1500. I never noticed them while I was going thru the grits.. Do ya start over sanding or try to compound them out?
 
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