Getting ready to paint my 70 chevelle (all spi primers, ppg dbc silver base and universal clear). Last coat of primer was wet sanded with 600, as I understand according to the 2k tech sheet it needs scuffed before base, what color pad will not mess up the 600 scratches but still surface it enough? I have maroon (fine) and gray (very fine).
which color scotchbrite pad after 600 grit paper-
- Thread starter bmenard
- Start date
Chris_Hamilton
Trying to be the best me, I can be
bmenard: If you want to scuff with a scotch brite pad it's perfectly fine to do so. Use the very fine (gray) and if you have it some, "Scuff Stuff", If not it will work just have to use a little more elbow grease. If you have sanded everything with 600 and have it completely uniform with no unsanded areas then you would not need to scuff it. If you have some unsanded or glossy areas then using a scotch brite pad would be beneficial. I'm not sure what Mike is referring to as I use them as a final scuff on everything I paint (collision repair).
MikeS
Camaro Nut
Hi Chris,
What I am referring to 'uniform' is what I have read here and elsewhere about Scotch-brite in that, let's say light gray (3M #7448) is 600-800 grit per 3M. Maroon 7447 is 320-400 grit. If the OP already wet sanded the final with 600 then I don't see a need for Scotch-brite.
What I am referring to 'uniform' is what I have read here and elsewhere about Scotch-brite in that, let's say light gray (3M #7448) is 600-800 grit per 3M. Maroon 7447 is 320-400 grit. If the OP already wet sanded the final with 600 then I don't see a need for Scotch-brite.
Jim C
Oldtimer
yes no need for scotchbite if you sanded already BUT you can use it if you wanted. i personally use maroon for everything in the shop. only ever use grey if i am forced to do a clear blend somewhere. i never see scratches in my metallics with maroon on primer. with grey i feel like im wasting my time. its just too darn fine.
Live and learn!
Chris_Hamilton
Trying to be the best me, I can be
Jim C;n82282 said:
I use grey for that reason Jim. Most of the time I've got a blend panel to do. Always found maroon too aggressive.
K
Kroozen
Barry does recommend in the tech sheet If sanded primer has set more than 24 hrs, you must scuff first with a red scuff pad or equivalent before applying another product
MikeS
Camaro Nut
Kroozen;n82297 said:
Another product I can see scuffing (due to no cross linking possibly from hours passed?) if it was leading up to preparing for the base coat. But the OP's next step was to spray base so, IMHO, he would not need to perform any further steps being he already used 600 grit on the primer. If he was applying a sealer then maybe scuff the primer but why even then being he already has the foundation done and I think this is where Jorge was going with his question (more about no scratch seen in topcoat when using a maroon pad and sealer). I got the impression the work the OP had done hasn't been sitting any length of time to need a cleanup scuff. Using a maroon pad would only reverse the grit finish from 600 back down to somewhere around 400. I've always have been under the assumption of 400 grit for a solid and 600 for a metallic base.
MikeS;n82298 said:
Its been sitting a week or so. The 600 came out good and even has a little shine to the primer, the maroon cuts the shine off and the gray does nothing. Ill probably just rub it with the gray, clean it and go. My only concern is seeing the maroon pad scratches, I don't want to go backwards after all the work to get it to 600.
Jim C
Oldtimer
jorge, normally i do seal but not always. sealer or no sealer i dont ever see scratches with a maroon pad. 400 grit hand block scratches i will see but if i rub the area with maroon then i can get rid of those and it comes out fine. maroon may be 400 grit or it may be finer, who knows. i always considered it more like 600g. if in fact it is in the 400 range then its just not cutting as deep and more uniform so your not seeing it in the finish. just like 400 grit on a da with a soft interface pad. you can do a metallic over that as well.
btw, yes i used the new 3m pads awhile back. totally bad ass. they seem really thin and light weight compared to any regular ones but they pretty much just keep on cutting until there is nothing left of them. im on my last box of old style. when thats gone i will only used the new ones from now on.
btw, yes i used the new 3m pads awhile back. totally bad ass. they seem really thin and light weight compared to any regular ones but they pretty much just keep on cutting until there is nothing left of them. im on my last box of old style. when thats gone i will only used the new ones from now on.
S
SmokeyHaze
While at school at PPG in Pittsburgh, a pretty obvious explanation was discussed about scuff pads. I love them, usually red only but sometimes are too aggressive. But was told to scuff first, then sand. That way the pad not being uniform or 100% grit of what it's supposed to be gets basically washed away with whatever sand paper your using.
He made a valid point of why sand, say a blend panel with 800, then go over it all and hit the edges with a red scuff just to make the some odd grit scratches back in. It's like wiping before you poop.
He made a valid point of why sand, say a blend panel with 800, then go over it all and hit the edges with a red scuff just to make the some odd grit scratches back in. It's like wiping before you poop.
crashtech
Combo Man & Mod
We've started using Norton Bear-Tex scuff pads, and have found the abrasive to be much more consistent in size, so the scratches are more true to what's expected.
i'm a little jealous of guys that say they never see scratches with a red pad. That is be true in areas where full coverage is achieved and the base has fairly good build, but in a repair environment like ours, red padding a vehicle exterior would be a total disaster. Gray pads do not appreciably compromise adhesion if the procedure is done very well (absolutely no gloss left) and the panel is squeaky clean. In over a decade we've never had a delam caused by gray pad use.
i'm a little jealous of guys that say they never see scratches with a red pad. That is be true in areas where full coverage is achieved and the base has fairly good build, but in a repair environment like ours, red padding a vehicle exterior would be a total disaster. Gray pads do not appreciably compromise adhesion if the procedure is done very well (absolutely no gloss left) and the panel is squeaky clean. In over a decade we've never had a delam caused by gray pad use.
Chris_Hamilton
Trying to be the best me, I can be
crashtech;n82325 said:
Well put Crash, exactly my experience and what i was thinking.
B
Beobob
Then I must not be scuffing right. Took a test panel (side of a microwave) and sanded half with with 600, scuffed the other half with 3M grey pad. Sprayed a base I was checking out the color of and cleared it. Looked great, ended up I will be using that color on my bike. A week or two later I took a putty knife to the panel. The sanded side was stuck like it was part of the original paint. The scuffed side came right off.
Just my experience, but no more scuffing for me. Sand with 600 every time.
Just my experience, but no more scuffing for me. Sand with 600 every time.