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-   -   can see sand paper scratches in basecoat (http://www.hotrodders.com/forum/can-see-sand-paper-scratches-basecoat-236138.html)

cletusvandamme 08-19-2013 03:35 PM

can see sand paper scratches in basecoat
 
I had to repaint a door and fender on my chevelle. Got all the right materials; sealer, activator, reducer, base coat, and clear coat. After mixing and applying the sealer over the spots I primed twice, I put on the base coat.

Where the sealer was sprayed I can see a bunch of scratches from the sand paper. There are no scratches where there was no sealer.

I heard from a paint guy that it could have been a incompatibility issue with paint and sealer?

I mixed the sealer correctly too, 4-1-1.

I was planning on trying to sand down the base coat with some fine sand paper to get the scratches out.

I also used only 320 on the sealer.

killeratrod 08-19-2013 03:43 PM

400 to 600 grit. 320 is still to course .


cletusvandamme 08-19-2013 04:11 PM

too coarse for the sealer?

how should I fix?

Preacherman 08-19-2013 08:21 PM

If i had to guess, i'd say the sealer caused the 320 marks underneath it to "lift". I know alot of people will disagree with that but i have seen it happen. Most sealers are pretty "hot" and will sometimes cause issues. 320 is fine as long as your not shooting a metallic color or trying to blend a panel. As far as fixing it goes...resand the base you have one the car now with 600. Recoat with more base and look for scratches...if they are still there, let the base dry to tack and 600 lightly, apply more base and so on til the scratches are hid. Once you have the scratches hid, apply a couple light coats over the entire panel and clear. Again, probably not the "by the book" way but it will work.

Preacherman 08-19-2013 08:27 PM

something else to consider here...some sealers don't set up very hard, therefore when you sanded the sealer with 320 it may have slightly clugged the paper which in turn scratched the sealer. Kinda like trying to cut clear to soon for a sand and buff job..it makes little hard chucks of material form on the sand paper and that will scratch the surface in a hurry. Anyway, if you follow the steps in my previous post...you'll be able to fix it all up in a hurry! God Bless!

carolinacustoms 08-19-2013 09:34 PM

"Where the sealer was sprayed I can see a bunch of scratches from the sand paper. There are no scratches where there was no sealer"

Yet another reason I don't like sealer. As stated, probably the best solution is to lightly sand the base with 600 wet and reapply a few coats. (just be sure the base you have can be sanded, some brands will cause you a lot more headaches if you sand them) If that is a problem, You could also go ahead and clear the panel, then after the clear cures, 600 wet and then base/clear. The clear in this scenario will seal the panel to prevent lifting or adhesion problems if you base cannot be sanded. Problem solved. The other option is to sand it all, reprime, 600 wet the primer and base again. Several options, you choose the course of action you feel best suits you needs.Hope this helps.

Kelly

Preacherman 08-19-2013 10:19 PM

agreed!...might be best to clear and then rebase/reclear over that. This way the clear acts as a sealer to lock down all the issues plus its thick enough to fill the scratches. Kinda like a sure thing this way...

69 widetrack 08-19-2013 10:38 PM

I have mentioned many times on this site that I don't like sealer....Sealer should only be used if you have a substrate that is suspect...or...you didn't prime the vehicle in the right shade of primer and need a sealer for more uniform color to achieve hiding with your base coat.

Sealer can be hot...sealer is another product to get dirt in...if at all possible, do not use sealer, it's not required when you do everything else properly.

Now, you have a problem...sand scratches where you have sealed the car. You can clear it, sand it and re-base over top of the prepped clear...no offense to anyone that suggested this, it will work...clear cost more than a 2K primer. Why not even out your substrate by applying 2 more coats of primer, it's cheaper, it's catalyzed and it's easier to sand. The base coat that you have applied will have gone past the recoatability or clearing window. Depending on the base coat you used, you can lightly sand the base coat with 600 grit wet paper, clean, tack and re base.

I hope this helps.

Ray

Preacherman 08-19-2013 10:45 PM

Yet another great point! My only issue is be careful the primer doesnt lift the base. I only say that because i seem to have trouble with lifting alot...lol!

carolinacustoms 08-19-2013 10:48 PM

Very sound advice Ray, I suggested clearing it because we have used that method a few times to "lock down" some problem areas before. Can't say that it is a text book way (or even the right way for that matter) but it is effective. However, I didn't think about the recoat window on the base. Since you mentioned that, I would agree with your suggestion of 2k, then base/clear, as the most effective solution.

Kelly

69 widetrack 08-20-2013 07:08 AM

I had a long day yesterday and when I posted...it was late...for me. I just reread your original post, what grit of sand paper did you use under the sealer and primer...How long of a flash time did you allow between coats of primer and sealer. You mentioned you needed to repaint a fender and door...why? Was there body damage? Did you use filler? How was the filler applied and over what? What grit of paper did you finish the filler in (if you used filler) before you applied primer?

I'm rereading your post and a step by step analysis of what you exactly did would help. Not only the proper way to repair the area but, if an error was made, so that we can correct it for you and explain what happened.

Ray

cletusvandamme 08-20-2013 07:13 AM

thanks for the answers

cletusvandamme 08-20-2013 01:40 PM

I sanded down the whole fender with wet 600. I couldnt get the marks out, so I primed over the marks. Sanded the primer down with wet 600 again. Got the fender perfectly smooth.

I go to spray the base and same thing happens. I get scratches in the base coat. Now in different areas. One area that has the scratches visible was an area without sealer or primer on it. Some of the parts I primed came out fine, some were worse.

It seems random? The top of the fender came our perfect as usual...

Also, its metallic paint.

I am going to try to sand down the scratches again and then clear coat it. I am running out of paint and it doesnt have to be perfect; whole car needs to be redone.

Should I wet sand the scratches with wet 800 or 1200 before clear coat?

cletusvandamme 08-20-2013 01:45 PM

Quote:

Originally Posted by 69 widetrack (Post 1706768)
I had a long day yesterday and when I posted...it was late...for me. I just reread your original post, what grit of sand paper did you use under the sealer and primer...How long of a flash time did you allow between coats of primer and sealer. You mentioned you needed to repaint a fender and door...why? Was there body damage? Did you use filler? How was the filler applied and over what? What grit of paper did you finish the filler in (if you used filler) before you applied primer?

I'm rereading your post and a step by step analysis of what you exactly did would help. Not only the proper way to repair the area but, if an error was made, so that we can correct it for you and explain what happened.

Ray



http://i13.photobucket.com/albums/a2...ps893ecfd8.jpg
This is how I bought it. Primer over a little bit of body filler. It wasnt that much body filler. The car wasnt dented, but more scratched from someone hitting a guard rail.

I only put some "red lead" filler in small chip parts.

I re-primed it and sanded with 180 (only the parts in primer in picture). Then I re-primed it a week later and sanded with 320; again, only the parts in primer in the pic.

I then sealed the primer parts.

I sanded the whole fender and door with 320. I had to get the old clear coat off because it had bubbles/bumps in it like someone had water in the compressor when they sprayed the clear.

I waited 2 days to put base coat on.

Door came out fine, no scratches.

Scratches in fender appeared over sealed areas.

That takes me today where I sanded whole fender with 600.

Then primed the parts that were scratched again, wet sanded with 600 after it dried for an hour.

Now its worse in some spots and better in others...


Again, car needs to be totally redone (note the bubble on the quarter, ect) It looks much better than it did, just up close you see the sand paper scratches. Running low on paint and dont want to waste more money, so need a quick fix before clear coat.

69 widetrack 08-20-2013 02:11 PM

Okay, that helps some. If your sanding final primer with 180 grit, my first question would be why. Final primed surfaces can and should be block sanded with either 400 dry paper or 600 wet paper. If you used a quality 2K primer, sanded the cured primer properly with the grits mentioned, sealer is not required.

When you final sanded, did you use guide coat. Guide coat will tell you very quickly if you have scratches in your substrate left over from the 180 grit you used when sanding the primer.

If you had bubbles in the existing substrate/paint, that is an indication as you mentioned that there are other problems underneath and I'm glad to hear that you realize that a complete "re finish" is required.

I may not be understanding correctly but, you sanded the primer 1 hour after applying it? If that's the case...stop...primer needs to cure longer than 1 hour before sanding...unless your using a 1K or lacquer primer...which...is not a good product to use...for base clear you need a quality 2K or catalyzed primer.

So, what kind of primer did you use, brand name, mixing ratios, etc. This information will help in getting your vehicle looking better until you redo the entire car...and it is great looking car by the way.

I sincerely would like to help, please post the information to the questions and we will get you on the right path.

Best Regards
Ray


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