What grit to use?

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PostPosted: Sat Sep 22, 2012 9:29 pm
I had to prep the two front fenders and hood to do a color change. we were going from a dark green to a silver metalic. i sanded the surfaces with 400 wet. but the painter said i should've sanded with 800. so i had to go over with 500 then a 800. need help understanding this..

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PostPosted: Mon Sep 24, 2012 7:28 pm
A metallic color, especially metallic silver, requires a finer grit paper than a solid color.
The metallic particles will collect in the sand scratches and show on more coarse grits than 500 or so.
This is why most product data sheets (tech sheets) specify to paint over P600 grit scratches for metallic colors. ;)



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PostPosted: Sat Sep 21, 2013 12:20 am
nice thread, altho by the looks of it your grading system is a little different to here in Australia, for solid colors ive been told 600w or 400 dry and metallic/pearls 800w or 500 dry, I get confused when I look at paper on the net to buy as the wet paper and dry paper grades are different, dry paper is finer than wet, so 500 dry is a little finer than 800wet paper, I never know which is which when buying online soi just stick to my local store, lol, but ive spent enough there they give me a pretty good discount now anyways!!



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PostPosted: Sat Feb 15, 2014 8:06 am
Great thread.

I've been advised by a couple of different mates who are in the trade, that if I'm painting on top of smooth, sound paint, I can go straight in with scotchbrite (scuff pads), panel wipe to make sure it's clean and paint straight on top.

Is this a bit of a risky bodge, or perfectly acceptable on top of sound paint? For example, I've got 2 good used wings (fenders) for the daily audi 80 TDI that have good paint but are in the wrong colour.

What's the view on a 'scuff and puff' job?

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PostPosted: Sat Feb 15, 2014 9:11 am
Well, clear coat is a great sealer. If it's sound, then no reason why it can't be sanded then painted over. Collisions shops do this every day, when blending in a repair.

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PostPosted: Fri Jun 20, 2014 1:27 pm
This is going to be very useful when I start my project.
"Never be afraid to try something new. Remember, amateurs built the Ark, professionals built the Titanic"



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PostPosted: Mon Jun 30, 2014 10:45 am
Best info i found:


36 grit roloc on small dent before filler 
80 grit to sand filler 
180 finish filler before high build primer 
180 first block on primer before second prime 
400 wet before sealer 
600 wet for blend areas 
800 rarely but occasionally start cut on a run 
1000 sand imperfections from basecoat, sand runs in clear 
1200 flatten orange peel 
1500 sand surface for factory orange peel look 
2000 for scratches in clear coat 
3000 trizac for easy polishing 

Grey scotchbrite- Prep plastic for paint(with scuff stuff), o.k. for hard to sand blend areas, or for not burning through the clear, may be used on sealer or base for recoating. 

Red scotchbrite- Prep new body panels for paint (best to seal over, but can be covered with basecoat) good for sanding before laying down stripes, o.k. for some jams.



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PostPosted: Fri Jul 25, 2014 12:21 pm
when dry sanding ..the paper clogs pretty quickly. Any ideas on cleaning the dust out of the paper grit ?

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PostPosted: Fri Jul 25, 2014 5:23 pm
Blow out the paper and area you are sanding with air frequently.
Use a wire brush on the sandpaper grit to remove clogs and blow off with air.



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PostPosted: Mon Jul 28, 2014 2:35 pm
didn't read everything just original post.

you have to go 800 grit minimum for waterborne paints. I've done 600 without issue but reccomended is 800 grit. Water doesn't fill much. Most here i assume are DIY so you aren't probably spraying water so it doesn't matter.

whole panel can be DA'd with 600-800 including blend area. I generally go 800. Pay attention to the orange peel flattening the more you sand, you probably want it relatively flat because there will be little orange peel after your clear spray added to however you leave it.

Generally i will use a gray scuff pad and get all of the edging after DA'd everything i can hit with the 800. I even go over what i DA'd and it helps flake everything for ez blow off.

I do blow off everything in and around...

Then Wax and Grease remover the whole panel, then wipe with microfiber in a pattern almost like i'm spraying to be thorough. I switched from rolls of paper towels to microfiber cloths since they are reusable and cost me about the same. In fact i feel i get more value with the microfiber. Wipe paper towers are so overpriced. wait about 5 minutes and do a final dry wipe.

then shoot.
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