Hello everyone. After long bouts of research and application I finally sprayed a vintage Mustang yesterday. Did 2 coats filler primer blocked it then a thin sealer/surfacer then 3 coats of silver Chromabase and 3 coats of ********** clear.

I didn't do a wet on wet primer to base. I sanded the last coat of surfacer with 400 (per the chromabase TDS) then shot base. I must have gotten debris in the paper or something because there's some very noticeable scratches on the top of of one fender and door that the Chromabase didn't cover. Reading now people are saying a silver needs minimum of 600 to hide scratches? That goes against the TDS.

I take it my only hope is to sand the scratched areas back down to the primer, wet sand the scratches out and then reshoot those areas? I have plenty of primer, paint and clear left over, anything special I'll need to do to blend? Any tricks to avoid sanding back down to primer?

Not a show car but they're visible enough to bother me. I'm not sure how I missed them, sanded primer looked flat as a mirror before I sprayed it.

Thanks.

Scared to pull it out into the sun this evening.

What does that mean? Wet on wet primer to base?

The tech sheet for Chromabase says sand primer with 400 grit "or finer"
400 is the coarsest you can use.
https://www.johnsonautobodysupply.com/m ... at-Eng.pdf

Also: Chromabase must be cleared within 24 hrs.
Left any longer than that you need to sand it all off according to
something I read a long time ago.

Did you paint over the previous paint job or strip it down to metal?

If you stripped it, then I would sand your clear coat with 800 grit to get it flat (no orange peel) and smooth. Clean it real good and then shoot your base and clear coats.

If you painted over an existing paint job, then you risk too thick of a paint layer on the vehicle, doing it this way.

Wet on wet: I mean I didn't have time to apply my base over the primer within the primer topcoat window so I had to sand it before applying the base. Looks like I definitely should have went to 600 or even 800?

I found several other spots where you can see the scratches too.

So now I suppose I have three options to pursue:

Strip all the effected panels down to primer and start over?

Sand down just the effected areas of the panels and blend into the existing paint/clear?

Or possibly just sand the clear on the effected panels and shoot base and clear over that as if it was just a recoat?

Kind of over it at this point. I spent so much time getting crappy repro sheet metal fit correctly and flat. Car looks absolutely perfect except for these scratches.

It was bare metal. Two spools of welding wire worth of restoration work.

Sanding the clear would be easy enough. I think maybe that's what I'll do.

The TDS for Chromabase says:

SURFACE PREPARATION
Prepare all surfaces to be repainted using the recommended undercoat systems, following
recommended procedures. Finish sand with P400 DA grit paper or finer (dry or wet).

There is a big difference between sanding by hand and sanding with a DA. A DA will not leave the same scratching that hand sanding will.

I've said this innumerable times, but, for the record:

For metallics and pearls, sand to a minimum (i.e. coarsest) P800 wet by hand or P600 dry on a DA. Results with a DA vary greatly and are heavily dependent on correct technique, high quality paper and use of an interface pad.

For solids, whether 2K DG or BC/CC, P600 wet by hand or P400 dry on a DA but, for most people it is much safer to stick with the P800 wet by hand or P600 dry on a DA.

In all cases you can go finer and still achieve correct adhesion. Up to P1500 wet by hand or P1200 dry is still okay, but sanding must be even all over the surface and there must be no shiny spots. Substrate must be properly cured/dry and any peel should be taken out first, otherwise you'll just be sanding the high spots.

"Sealers" vary enormously but most of the ones that I've used, whether epoxy mixed as a sealer or specific 2K sealers, are non-sanding unless left (usually overnight) to harden. Generally the correct procedure with a single coat sealer is wet-on-wet, allowing the sealer 20-60 minutes before basecoat. Following the TDS is essential because they can be so different. The problem is that while the sealer might appear "touch" dry it isn't fully hardened and sandpaper can tear the surface, leaving scratches that will be visible later.

In this case, since the panel has been cleared, a fix can be achieved by sanding the clear with P800 wet to take out any peel, then respraying base and clear. Be very careful that you don't sand through the clear, which will then require re-application of primer on the sandthrough. Alternately use P1200 or even P1500 wet to give you the required keying.

Using a correctly shaded sealer or primer will reduce the number of coats of base needed to achieve coverage. For this rectification, 2 coats should be enough and shouldn't affect your DFT to the point where paint performance is impacted.

Thanks fellas. I'm going to just go ahead and respray over the clear as you recommend. Good news I way over ordered on clear and will only need another quart or two of base to respray the whole car. Just some more elbow grease and a lesson learned hopefully.

NFT5 wrote:The TDS for Chromabase says:

SURFACE PREPARATION
Prepare all surfaces to be repainted using the recommended undercoat systems, following
recommended procedures. Finish sand with P400 DA grit paper or finer (dry or wet).

There is a big difference between sanding by hand and sanding with a DA. A DA will not leave the same scratching that hand sanding will.

I've said this innumerable times, but, for the record:

For metallics and pearls, sand to a minimum (i.e. coarsest) P800 wet by hand or P600 dry on a DA. Results with a DA vary greatly and are heavily dependent on correct technique, high quality paper and use of an interface pad.

For solids, whether 2K DG or BC/CC, P600 wet by hand or P400 dry on a DA but, for most people it is much safer to stick with the P800 wet by hand or P600 dry on a DA.

In all cases you can go finer and still achieve correct adhesion. Up to P1500 wet by hand or P1200 dry is still okay, but sanding must be even all over the surface and there must be no shiny spots. Substrate must be properly cured/dry and any peel should be taken out first, otherwise you'll just be sanding the high spots.

"Sealers" vary enormously but most of the ones that I've used, whether epoxy mixed as a sealer or specific 2K sealers, are non-sanding unless left (usually overnight) to harden. Generally the correct procedure with a single coat sealer is wet-on-wet, allowing the sealer 20-60 minutes before basecoat. Following the TDS is essential because they can be so different. The problem is that while the sealer might appear "touch" dry it isn't fully hardened and sandpaper can tear the surface, leaving scratches that will be visible later.

In this case, since the panel has been cleared, a fix can be achieved by sanding the clear with P800 wet to take out any peel, then respraying base and clear. Be very careful that you don't sand through the clear, which will then require re-application of primer on the sandthrough. Alternately use P1200 or even P1500 wet to give you the required keying.

Using a correctly shaded sealer or primer will reduce the number of coats of base needed to achieve coverage. For this rectification, 2 coats should be enough and shouldn't affect your DFT to the point where paint performance is impacted.

on the sealers! the only time 400 MIGHT be suitable, is to use the sealer over it then your color NO sanding of the sealer. be careful with the sealer if you tack rag just before your color, most will stay soft and real soft in heavy spots (horizontal concave areas) your tack rag will snag the sealer and then there will be tears running down your face.
Jay D.