[Jimbo17]

About four years ago I had my van painted.

It is a base coat clear coat and the problem is on the roof area only the clear coat is lifting.

The base coat looks fine. Can I sand all the clear coat off and prep the roof again and shot it or is this asking for trouble?

I used a Matrix paint at the time not sure if this matters or not.

If I was going to sand just the roof area should I use a 320 or something like a 400 to prep it?

Thanks for your help. Jimbo

 

[swvalcon]

You will have to sand the roof down with 320 then recoat with a coat of color then reclear. you can't just reclear what you have.

 

[mike the painter]

Just being curious but what kind of clear did you use and how many coats?

 

[mitmaks]

You will have to sand the roof down with 320 then recoat with a coat of color then reclear. you can't just reclear what you have.

Whoa, hold on there. 320 is way too coarse, unless you're going to do some priming/bodywork. I'd wetsand with 600 and shoot 1-2 coats of color and re-clear.
p.s. Might have to seal it to prevent lifting and have better base coat adhesion.

 

[swvalcon]

The only time I sand with 600 or finer is if all i'm doing is blending a panel and reclearing. Other wise I always go 320-400 if its going to get 2-3 coats of color and 2-3 coats of clear. If done this way you shouldn't see any sand marks. Thats why so many guys jobs end up peeling their afaird to rough up the old paint a little.

 

[mitmaks]

You might get away with 320 under solid colors but for metallic I wouldn't use anything coarser than 600.
As far as paint job delaminating-some people wait too long before topcoating/clearing.

 

[TucsonJay]

I use 360 under any base coats. for clear coats I use 600 minimum. I would rather "ere on the side of caution", and always have good adhesion, so I always use a little rougher grit than the industry favors.

Something is working, since I haven't had paint peel on a job in a few decades.

 

[mitmaks]

I've seen too many "dealer lot" paint jobs with sandscratches in them. A coat of epoxy as a sealer is better than 320 grit sandscratches showing up imo

 

[Jimbo17]

Sanding

One thing to remember is this is the roof area of a van that I am doing so maybe sanding with 320 and then I want to prime it and use a sealer before spraying a few coats of base and then the clear.

Should I use a 320 and wet sand the whole area or can I use 320 on a DA?

Is there such a thing as a primer/sealer or are they two separate steps?

Thanks Jimbo

 

[swvalcon]

I would use 400 on a da. 320 dry or 400wet. Then use a 2-k sealer or a coat of epoxy. Then put down a good coat of base giving each coat time to set up between coats. There nothing worse than rushing your base coats.I always give mine at least a half hour to 45 min. I'am a restoration shop so I dont have a high paid ex detail guy wineing about how much time I take. I wait 2-4hrs and put on the clear giving it about a hour between coats.

 

[mike the painter]

You might get away with 320 under solid colors but for metallic I wouldn't use anything coarser than 600.
As far as paint job delaminating-some people wait too long before topcoating/clearing.

I do it every day...320 DA ,2-3 coats of base then clear..I've never seen anybody sand a car with 600 .....even If I'm blending I'll 320 da where the color is then 600 DA the blend area and the rest of the panel....I never use a sealer just a few coats of base on the primer spots before I start painting....Thats what I've used for my production work for the past 20 yrs..If your getting scratches showing through with 320 DA your not getting enough paint on, 2-3 coats of any base is plenty ...
Now,hand sanding and wet sanding is different. When wet or dry sanding the coarsest you can use would be 400 before you can paint....The only time I use any kind of sealer is when I'm doing a complete paint job thats been completely primed and blocked(by hand) and then its an epoxy primer reduced to a paints viscosity..

 

[tech69]

I wouldn't do a 320 on a light silver but I haven't seen any issues from using a 320 and I know quite a few guys who use it. The only time where I saw procedural issues in regards was a guy who used 220 on his primer then sealed it with a 2k mixed a tad thick. Soon as the sun hit it the thing shrunk and revealed huge scratches. It was a silver car. In our shop in the body area we block with 320 dry then it goes to the paint area and the painter uses a scuff pad with a piece of 600 da paper on top and goes over it real quickly but not guide coated or anything. Just kind of buffers out our scratches a bit. I think if there was a problem with 320 scratches it would have some to do with the color and/or sealer pinching up as it cures.

 

[swvalcon]

I've seen sand swelling on 320 if you load up your base coats giving the solvets time to bite into the primer. Just give your base time to completely flash off between coats and you wont have any issues. I've even used 220 on a soild single stage used car job and been ok.

 

[mitmaks]

Like usual, you ask 10 painters how they paint and you'll get 10 different results. It's really up to the painter to decide what he prefers. It mostly comes from experience, none of us became great painters overnight. We all learned from our successes and mistakes.

 

[cyclopsblown34]

Like usual, you ask 10 painters how they paint and you'll get 10 different results. It's really up to the painter to decide what he prefers. It mostly comes from experience, none of us became great painters overnight. We all learned from our successes and mistakes.

Speak for yourself...I'm still a rank amateur. I learned the other day from my friend who messed up the hood for my son's truck that you can spray activator directly on sun dried non activated clear and it'll work perfect, I also found out you sand previous clear to 1000 grit and reclear. Needless to say, I'll let him do airbrush work(he's an awesome artist) with materials I mix up and I'll spray the clear.

 

[Lizer]

So some of my panels are in SPI 2k (fenders, valances, tail light panel), while other panels are in Slick Sand (doors, roof, quarters, hood, trunk lid). To have a final uniform substrate I'm going to seal everything before base, but from what I'm gathering if I do a final dry block of everything with 320 that should be sufficient for seal coat epoxy?

 

[tech69]

In my opinion that depends on the color. If it's going black or silver 400-600 is the way. There's benefit to both...adhesion or guarantee that minute scratches don't show. On one hand I can see adhesion being better with 320 and on another I can see a car cut flat to where you don't want to cut it flatter later when the sun settles everything and barely visible scratches appear. If you want the best of both worlds do 320 and leave some orange peel. Then two years later when you've added some superficial scratches and swirls through some wear and tear you have more material to cut out and shine while getting the 320 scratches out. When I do my car I'll probably go 320 cause it's white and if it wasn't I'd go 400. In any case, I'm leaving some peel initially so I can play with it later. No point cutting it flat to show off now when the darn clear helps fight UV rays. I want this baby to last and in doing so that means leaving a little meat on it to play with later. just my opinion.

 

[Lizer]

Are you responding to me? I'm talking about final block grit of high build primer (some of it being Slick Sand so I don't want to wet sand) before sealing with epoxy. There won't be any orange peel.

I was not planning on blocking the seal coat epoxy and shooting straight over it with bc 2 hrs later per Barry's instructions. I can get the epoxy to lay down completely smooth with no peel so it shouldn't be an issue. However, if I do end up getting peel (as luck would have it...you know, getting peel when you actually aren't trying to as opposed to the times when I didn't get peel and wasn't necessarily not trying to) then I may have to cut down some of the peel.

I'm painting mine a metallic blue (the 97 Dodge Viper blue).

 

[tech69]

metallic blue will show scratches. If you want to dry sand maybe try what we do. We get it all with 320, then the painter goes back over it by hand with 600 da over a scuff pad. He doesn't guide coat it but I can imagine a light spray of guide coat would be ideal. When I first worked here I wasn't sold on the 320 thing but I'm a product of my surrroundings. Later I found out the process we use doesn't have issues later with scratches.


We do final round with 1-2 coats of primer. One coat gets 320 and quick rough over with 600. 2 coats get 220 then 320 then a rough over of 600. The only thing I'd change is spraying a real light and even coat of guide coat for that 600.

I've worked at two of the top restorations places in Sac County and BOTH shops do dry sanding only.

I will say...nothing makes a car more crisper then a 600, especially for metallic. But is the adhesion as good? I don't know and it's hard to put a button on why it makes it look so crisp but a 600 on a metallic goes very well with staight body work. It's like the icing on the cake. Me and a bud were comparing scratches and couldn't come up with a term or why a 600 made it pop but that's it, it makes it pop much more. I equate the popping to the same kind of pop you get when you cut your clear with a hard block. I'll just say it adorns good quality work.

 

[mike the painter]

It sounds like your on the right path...The problem I have is when I spray the sealer (epoxy) it NEVER lays down as niceand slick and dirt free (even in my booth) as I want so I always sand it (lightly) with 600 wet paper with very little water just enough to keep the paper from clogging but never enough to run off onto the floor or in the janbs,I feel its better to sand it anyway...if your not going to sand the sealer coat be double sure theres no trash anywhere or youll be sorry when the cut and buff time comes..theres nothing worse than when a piece of black trash raises its ugly head through your perfect paint job.