Colour sanding - FFCars.com : Factory Five Racing Discussion Forum

garnet · 10-07-2012, 01:10 AM

Hi, I'm colour sanding single stage black and am noticing that after everything is perfectly smooth and all the orange peel is sanded smooth (completely, there is no 'shiny' left), but there is still a sort of 'orange peel shadow'. It's flat, but has the pattern of orange peel (you have to be up close and really looking).

Some parts look more monotone and even, like the right side near the edge, but most of the rest has this mottling.

Am I doing something wrong in the painting stage? Or do I need to sand more? I could try but don't want to burn through. I haven't buffed this yet so I could try that and see how it looks, but buffing just seems to make any flaws more noticeable so thought I'd ask first.

btw the paint seems to have a fair bit of orange peel when it goes down although a paint guy said it looked normal to him.

Thanks.

mrmustang · 10-07-2012, 01:14 AM

Quote:

Originally Posted by garnet

Hi, I'm colour sanding single stage black and am noticing that after everything is perfectly smooth and all the orange peel is sanded smooth (completely, there is no 'shiny' left), but there is still a sort of 'orange peel shadow'. It's flat, but has the pattern of orange peel (you have to be up close and really looking).

Some parts look more monotone and even, like the right side near the edge, but most of the rest has this mottling.

Am I doing something wrong in the painting stage? Or do I need to sand more? I could try but don't want to burn through. I haven't buffed this yet so I could try that and see how it looks, but buffing just seems to make any flaws more noticeable so thought I'd ask first.

btw the paint seems to have a fair bit of orange peel when it goes down although a paint guy said it looked normal to him.

Thanks.

With todays "non lead based" paint toners, you will never get it 100% smooth as glass. That is the limitation of a single stage enamel or urethane based single stage paint job.

Bill S.

garnet · 10-07-2012, 01:21 AM

Thank Bill, but I'm a little confused, I think physically it is smooth it just looks mottled.

Does the mottled look come from the fact that it isn't actually physically flat, or something else?

I went with the single stage because the ones I've seen look deep and even, maybe I wasn't looking hard enough?

Riptide Motorsport · 10-07-2012, 02:42 AM

Buff a spot and see how you like it, buffing a spot will show you the answer to your question. Steven

garnet · 10-07-2012, 02:51 AM

Okay, thanks, will buff tomorrow. Speaking of which I've only done a bit of buffing and used an orbital unit. It looked like it did okay on the test pieces I had, but someone said you need the rotary ones as they are much faster and generate heat.

Thanks.

Riptide Motorsport · 10-07-2012, 01:15 PM

You will need the rotary buffer with the wool bonnet to do a proper job. The harborfrieght one will work for you.

garnet · 10-07-2012, 05:23 PM

A bit more sanding seemed to remove the mottled look and the waviness that existed in the buffed version.

Thanks for the help, end result seem good so far, now I just have to get that in the rest of the car.

Is it advisable to let the paint cure a bit before cutting/buffing, or is it okay to do right after colour sanding?

Thanks.

JCCLARK · 10-10-2012, 10:54 AM

Wavy?
Sounds like "urethane wave"
Quite different than orange peel.
All clearcoat jobs have it and most don't even notice it.
You won't remove it by sanding out the orange peel with fine grit
papers, like 1000 grit and above.
If you want a completely "straight" (no waves) paint job you have to use a
coarse grit paper like 400 to 600 for the first clear sanding.
Most freak out when they hear that but that's how a true
"show car" paint job is done to get it dead straight.
Here's one started with 400, notice the straightness of the reflections.
and one sanded with 2000

garnet · 10-19-2012, 06:17 PM

Thanks JC, that confirms what I've been doing, and good to know that I can go even a little courser than the 600 grit I've been starting with. The finer grits seem to round out the orange peel, while the courser grits cut through it.

I'm using single stage btw.

I've been cutting most of the orange peel off with the 600, then go to 800 when there are just small shiny spots (deepest parts of the orange peel), when they are gone I go to 1000, 1500 and 2000 to remove the scratches. I've been a little concerned about burn through so haven't removed all the orange peel with the 600, but I might try that.

I got some surprised looks when I've told painters that I'm starting with paper that course as well.

Terrorist Hunter · 10-19-2012, 07:23 PM

Garnet, that shot of the door looks really, really impressive. A black that turns almost white or light blue in the sun is always stunning, can't wait to see it when you're done!

garnet · 10-26-2012, 12:24 AM

I've currently sanded everything down to 1500 grit and was planning to do 2000 and the cut/buff. However I've just noticed a few of these white specks in the paint. I haven't noticed them until now and I'm guessing they are bits of dust caught in one of the layers that were covered over with more layers of colour paint and that I've sanded down into them.

Anyone familiar with these and what the best approach might be? Keep sanding that area and see if it removes them?

Thanks TH, I'll post the finished product when it's done.

JCCLARK · 11-02-2012, 11:53 AM

All you can do is try and sand it out, if you go through
you'll have to repaint.

garnet · 11-09-2012, 11:13 PM

Thanks JC, seems that works so far.

One more thing (so many learning curves), I started colour sanding with 600, then 800, 1000, 1500 and 2000 and am noticing a lot of scratches. I've been going over the areas again with 1000, 1500 and 2000 but a lot of them still remain.

I didn't notice this in the first panels I did, but maybe I slacked off on the higher grits in subsequent (and larger) panels. I thought it might be my buffer (orbital, as mentioned here that they don't generate enough heat) but the first few panels were fine so I tend to suspect the sanding. I've sanded the areas quite a lot, but I guess the paint is harder now.

Any suggestions?

Thanks, as always.

JCCLARK · 11-13-2012, 11:19 AM

It's always a challenge to get rid of the coarse scratches completely
on the second sanding.
I've started using 1000 to 1500 discs on my finish sander and
sanding the clear dry after the coarse hand sanding.
It shows the first scratches up while sanding, I can actually see
them disappearing while sanding.
The first hand sanding is long straight scratches, the palm sander
is orbital so it contrasts nicely against the long ones.
I wear a cotton glove and wipe as I go, I also run the finish
palm sander on half speed. Seems to work best for me.
The 3M film discs work best but they are expensive.
I can go from 600 hand sanding to 1200 discs on my palm sander
and easily remove the 600's.
After the 1200, I wet sand with 2000.
Everyone has a different progression, you have to find what works for you.
But seeing the scratches leaving makes it a lot easier.
Some even guide coat their clear between steps.

garnet · 11-20-2012, 10:42 PM

Thanks JC, I think I'll give that a try, especially since part of the problem is not knowing what grit of paper made the scratches. I've been wondering if some of the scratches are new ones I've created with junk caught under the paper (I'm learning to be more careful in the finish sanding).

At one point I was sanding each grit in a different direction, but that's difficult to do in some parts of the car, so at this point I'm not sure what their origin is.

Thanks again, back at it.

Arrowhead · 11-21-2012, 03:16 PM

As painful as is, make sure you use the highest quailty paper you can get like a Norton or 3M (I'm sure there are cheaper but just as high quality alternatives). The cheap papers in the fine grits will leave deep scratches and you will chase them until all the paint is gone. Not sure if that the problem you are having, but just keep it in mind when buying supplies.