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how far to sand old paint

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Old 02-10-2018, 04:05 PM
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Lyndwood
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OK, decided wrapping the car is not in my budget and I want to drive the car this year. I decided to go with the color that was on the car (91 corvette Turquoise Metallic but it needs a re-spray. so how far would any of you take down the existing paint to re-shoot the car for a garage paint job. now the condition of my paint now is 70% is good, still shines looks great. the other 30% has either been nicked /scratched and needs minor repair (filler) or the paint is spider webbed and flaking off most likely due to bad prep the last time it was painted in the 90's (around the side mirrors mounts and door handles and the tops of the fenders).
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Old 02-10-2018, 05:14 PM
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ignatz
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You need to at least get past any clear and then put a good primer/sealer down. There is a paint and body forum under 'General Corvette Topics' that's best for these questions.
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Old 02-10-2018, 06:24 PM
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Originally Posted by ignatz View Post
You need to at least get past any clear and then put a good primer/sealer down. There is a paint and body forum under 'General Corvette Topics' that's best for these questions.
yes I planned on doing that, just didn't want to have to strip back to raw FG like some people are telling me to do. I also reposted this in the paint section, thanks for the info.
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Old 02-11-2018, 01:20 AM
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If some of the paint is flaking and spiderwebbing due to poor preparation last time I wouldn't take a chance on any of it, I'd remove it down to the fiberglass or the original GM primer coat if its still there.
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Old 02-11-2018, 01:52 PM
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Or clean up and touch up the bad 30%, knowing you are doing the whole car sooner than later. One quick layer of acrylic enamel won't add much to the total prep when you are ready to do the car.
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Old 02-14-2018, 06:06 PM
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george2066
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Default I will be doing the same someday

from what i have been reading, be careful not to sand off the sharp lines of the car
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Old 02-16-2018, 08:11 AM
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jimvette999
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I would block sand it down to the original topcoat and apply an epoxy primer. The epoxy primer thinned to spec can/should be used as a sealer. After that, you can apply the primer un-thinned as a base to block sand and then apply your topcoats. Factory paint will make an excellent base. You get into problems when you apply finishes over too many layers of existing paint or over incompatible materials. For example, if prior painter used "fish-eye" remover which is silicone based, you'll have problems trying to apply a finish over that. Even sanding it off will spread/embed the silicone into under coats. Once fish eye remover is used, it has to be used in subsequent top coats. I would just do the hood or a fender to see what you're getting into before tackling the entire car. You may also encounter hidden body damage. You can look for that by examining inside the fender wells for repair materials. Using epoxies and paints without a proper respirator can cause neurological damage so use a good respirator with the right filters....very important. If you're new to painting, I recommend you practice the entire process on a junkyard hood. Choosing the right sand paper grades, blocking shapes/practices, paint application techniques, & dust/bug control....etc. Good lighting is important. Laying on the paint as a tack coat, medium, wet, medium wet, final topcoat, & then clear (if applicable). Reading the mixing instructions, flash times, pot life of the product. Temps and humidity play a big factor in all the cure/flash times. You can end up with sags/runs a lot quicker in cool temps. You can end up with orange peel/overspray issues in hot arid climate. You add/reduce thinners to compensate in addition to wait times. There's a lot more to painting a car than a rattle can paint job on a lawn mower. Is all in the prep work but the paint application/technique needs to be done properly too. Do it right and you can avoid color sanding. Do it wrong and it will look poor. Paints and epoxy primers are expensive....make sure you want to do this right before dropping hundreds of dollars on a good gun, compressor, and supplies. Good luck to you.

Jim

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Old 02-16-2018, 01:02 PM
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Originally Posted by jimvette999 View Post
I would block sand it down to the original topcoat and apply an epoxy primer. The epoxy primer thinned to spec can/should be used as a sealer. After that, you can apply the primer un-thinned as a base to block sand
Jim
After you apply that thinned epoxy primer as a sealer, do you let it dry completely and sand before applying the unthinned epoxy primer, or do you apply the thinned epoxy primer as a sealer and then before it dries completely apply unthinned epoxy primer?
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Old 02-16-2018, 08:13 PM
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Yeah, let it cure then lightly sand/scuff with 320/380 to get a mechanical bond and lay on 2-3 wet coats of primer to block sand (if needed). You'll sand 1-2 of those back off in the blocking process. Keep in mind, sanding is not nec. between any applications of primer as long as you follow the spec sheet the paint shop should give you. You have hours in most cases and once the window closes, you have to go back to mechanical bond (sanding) vs. chemical bond. Technically you don't have to wait between sealer and primers but as a preference I would just to check for reactions and result. You can have your primer tinted to more closely match your paint color too....dark gray in your case. I would also tint my sealer stage a darker/different color than sanding/blocking stage so you know when you're going too deep on a body line or sealer coat. You can ask them for a small amount of tint that you can add yourself, say red for example. The spec or data sheet is handy for mixing ratios/recommendations. I like Dupont or PPG. Avoid budget brands or even house brands from PPG called "Shopline", I've had longevity problems when I do. Duponts DP40 epoxy is good, stay with one brand for sealer primer, & topcoats. Use ultra light pressure when using the tack cloths and use wax & grease remover before you start sanding and after you sand before applying anything. Little dish soap and water is good before that to really get the dust out of the hidden recesses/door jambs and even the scratches in the primer from the sanding. It'd best to remove as much trim as you can. I like to paint the doors, tops and hood off the car, you may not. This allows you to paint the car back half/front half separately by days apart if you want. It's more managable but you'll waste more paint/primer this way because you'll always have leftovers in your gun. Pot life varies. And finally, I like to wet sand, it keeps the dust down, keeps the sand paper clean and cuts better. Finish off with 400-500 grit prior to laying down the paint or sanding scratches will show. Don't go finer than 500 or you'll not have the bond. Using mettalic will require that you stir well and keep you cup moving/swirling to keep the flake in suspension. Ask the paint shop "flexible bumper system recommendations" as you may have to buy an additive for flexible parts and paint those separately (bumper covers). Take your time and remember, it's the prep work that pays off in the end.
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Old 02-16-2018, 09:08 PM
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Originally Posted by Lyndwood View Post
it needs a re-spray. so how far would any of you take down the existing paint to re-shoot the car for a garage paint job.
just pointing out that all the OP wanted was a quickie respray
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Old 02-19-2018, 08:38 AM
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Originally Posted by ignatz View Post
just pointing out that all the OP wanted was a quickie respray
I thought about that but when he asked how far to take it down, there's only one path back to the top to get a nice end result with some guarantee of success. Since he asked that specific question "how far to take it down", it told me he wanted a certain end product. Otherwise, just degrease/wax, scuff, prime and topcoat. But you're right, he did want a budget respray, not what I detailed.
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Old 02-19-2018, 04:28 PM
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Originally Posted by jimvette999 View Post
I thought about that but when he asked how far to take it down, there's only one path back to the top to get a nice end result with some guarantee of success. Since he asked that specific question "how far to take it down", it told me he wanted a certain end product. Otherwise, just degrease/wax, scuff, prime and topcoat. But you're right, he did want a budget respray, not what I detailed.
It was originally going to be a scuff and shoot so I could just drive it but with having to repair some spots It will be more than that. If there is a middle ground between the two, thats what I'm doing
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