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Old 04-09-2008, 08:25 PM
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Sanding back my (less than awesome) first paint effort to paint again

Hi Everyone,

I would greatly appreciate any advice as to the best course for sanding back my first paint effort for a 2nd go.

My main problem the first time (among a few others) was that I tried to skip sanding the primer. The finish is definitely less than smooth. I finished it out at the time with the clear though, b/c I didn't know any better. Now that the weather is warming back up, and I've read a LOT more about car painting, I think that I'm ready for another go.

Unfortunately, I haven't found a whole lot of info about my exact situation. How should I best sand back the first paint and to what surface level? Can I start with 80, 180 sandpaper to cut back the clear coat and start working up to 240, 400, 600? The clear coat needs to go all the way I think, but is my base coat a good substrate?

When I painted it the first time, I sanded the car's original paint, then shot primer on that, base coated, clear coated.

Thank you all. Regards, Eric

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Old 04-09-2008, 10:48 PM
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hopefully you won't need to go as coarse as 80 to smooth things out. I would start sanding with a finer grit and see where its getting you. You could step down grits, but you can't take too big of a jump, and have to make sure you have the coarser scratches removed with your finer grit. Start with 320 on a orbital palm sander or da, and see where thats getting you. If its getting it smooth, you may be able to just run over it again with 600 wet and paint.

If its fairly bad, maybe the easiest would be sanding with 180 or 220, and then spraying a coat or two of epoxy as a sealer(sealing would be the safest anyways) the day prior to repainting. Also this should help prevent possible lifting if you cut the clear thin in an area when you spray your new base on. As long as you spray your base within the epoxys open window, the base will have chemical adhesion to the epoxy. So if your sealer doesn't lay quite as flat and nib free as you would like to begin spraying your base on, say you only want to flatten a bit and take out nibs, you can hit it even with some finer like 1000 wet to smooth and remove nibs, and not worry about the grit being too fine or missing a spot (cause still have chemical adhesion). If the epoxy seal coat looks good, then you could just base without sanding it first. Epoxy should fill 180 grit, check the product sheets for you epoxy to see what you need to get down to.

The thing that concerns me though as you said you didn't sand your primer well. Hopefully the base you applied the first time around on the non sanded primer (how long did the primer sit before you sprayed base?) is adhering okay and doesn't end up lead to early failure.
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Old 04-09-2008, 11:23 PM
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Thanks so much for the advice. I think that I'm going to have to go with the "fairly bad" scenario you listed.

The unsanded primer was pretty rough, definitely classic orange peel I should clarify. I made quite a lot of mistakes I'll admit. 1) I shot the entire car inside and out at once. 2) This caused me to have to shoot from a greater than optimal distance in a lot of spots, thus the peel..

So do I need to go back to primer level then to eliminate the orange peel from where it started? Just a lot of P180ing, and then lighten up as I'm getting to that level?

Kenseth, can you, or anyone else, comment a little more on the sealer you mentioned? I've read about it in passing, but it hasn't been a part of my paint plan yet. Is it just a primer that provides a good substrate, but that's not for sanding, like a primer-surfacer would be?

The base was shot on the primer less than 8 hours after primer.

Thank you!
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Old 04-10-2008, 03:39 PM
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Sealer would be like a primer, but normally sprayed just before paint, and less viscosity then primer so it will lay down flat. Normally a sealer doesn't have to be sanded if it is sprayed well, and the paint is applied within the allowed time in the product sheets. There are also products meant just to be used as a sealer, but also many urethane and epoxy primers can be used is a sealer, normally by extra reduction then if it were going to be used a sealer. Many product sheets give mix ratios to use as a primer and mix ratio to use as a sealer.
By using a sealer, you can sand your surface a bit coarser then if you were not using one, and were just to apply base over the sanded surface. Spraying a sealer will also mean less chance of incompatability between old and new coat, or something like lifting at a breakthrough or feather edge. Get the product sheets for the materials you will be using, and follow them. They will give instructions for proper use and precautions. In case of your sealer, the product sheets should also state what grit range the surface needs to be worked down to for the sealer to fill.

Not sure what you will need to sand with in your situation, or if you will end up going back to your primer coat. May not be a bad idea if you didn't sand it very well before painting the first time.
Start sanding with various grits, and see if you getting anywhere with that grit If not, try a bit coarser, and step down going over again with a finer grit if you had to go coarser then your sealer recommended to get anywhere. You will have to look at the surface you sanded and see when it looks and feels smooth, and you don't still see texture-orange peel.

You could also apply a guide coat a contrasting color if it will help you see areas that will need more sanding. It would really have to be pretty bad orange peel if machine sanding in the 220 to 180 grit range isn't effective at sanding it flat.
Shooting at two far a distance I would think would cause a dry spray surface more then orange peel. Orange peel is more prone to be caused by applying too heavy, too low of pressure, material too thick, or the spray gun tip size being too large.
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Old 04-10-2008, 10:12 PM
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Kenseth, you're awesome. Thank you. The advice is invaluable.

I'm not really sure what caused the orange peel. I can say that the primer I used (Dupont ChromaSurfacer) took no kidding an hour and a half to stir into solution. The bottom had just settled stiff. Maybe it had sat too long or was old?

Also I should admit my first gun was definitely suspect. I have a Finishline now, and hopefully it will pull through just fine for me.

Okay, I'm going to hit the books and really try to know what I'm doing this time. Should be painting in about 2-3 weeks. Weather will be perfect.

Is it okay if I shoot you an email if I have any final technique questions, or just post another thread? You definitely know what's going on with painting, and I'd like to rock it this time around.

Thanks, Eric
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Old 04-11-2008, 03:49 PM
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Feel free to pm me if you'd like. but if you run into more questions, you may want to post up a thread about it. There are a lot of different backgrounds and experiences on here, including some who know the chemical side of things better, and its sometimes nice to get different opinions, maybe someone has a better way of doing something. Always use to get a few different responces to questions on here, others were just slacking on this thread.
Maybe the question-thread you post will end up helping someone else with a similar question. Don't forget to use the search function as well, so much has been covered here over the years, including some replys from knowledgeable past members that no longer post here.
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