Sanding scratches - painting novice

thethee

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The paint that is currently on my Imperial is really bad, it's faded flat greyish. It had a slight mad max kind of feel but when I pulled it out of hibernation it just looks sad. So I'm gonna try my hand at painting this spring.

Having never done this before I thought it best to start with something small to learn so I took off one of the headlamp doors for testing.

I sanded it down with 180 grit to remove the existing orange peel. Followed with 240, 320 and 400 grit changing direction ~90 degrees between grits. All wet block sands by the way. Prepped the surface with degrease and gave it 3 coats of single stage gloss black.

The issue I'm having is that even though the coverage seems great I can clearly see the sanding scratches show through the paint.

Did I not use a fine enough grit or should I use a machine instead of by hand? I thought since the current paint is on okay I wouldn't need primer, did I assume wrong?

I'm aware painting is an art so I'm not expecting perfection but would love some pointers and try something new. :)

Tried to take a picture but it doesn't really show
 

stubs300

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Buy a book about auto painting and read it, watch a LOT of youtube videos about auto painting, etc. Know any people that paint autos? Talk to them! You'll learn lots more than you can with this topic by people that aren't painters but think they know everything about everything! Good Luck
 

Justin Plant

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Before you lay down any paint, you should only be able to see a uniform haze on the surface. No individual scratches. Go all the way to 2500 or 3000 grit. Rub your hand across the surface. If you can feel it, you can see it. Be patient, its nor a quick process. Good luck
 

azblackhemi

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Starting with 180 is too course of a grit. Even going over with finer grits you probably still didn't get all the deep scratches out. 320-400 is about as course as you want to use unless you are priming or putting down a sealer.
 

thethee

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Before you lay down any paint, you should only be able to see a uniform haze on the surface. No individual scratches. Go all the way to 2500 or 3000 grit. Rub your hand across the surface. If you can feel it, you can see it. Be patient, its nor a quick process. Good luck
I would've thought that is too fine a grit and would mess up paint adhesion?
 

volksworld

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2500/3000 is way too fine....thats what you use on clearcoat prior to buffing...and if all you were doing was trying to remove orange peel i would have started with 320...and many new paints dont play well with original finishes, solvents can attack previous finishes and raise the edges of sanding scratches...the "right" way to do things is media blast everything off and start with compatible etch prime, fill prime, sealer, then color...with appropriate sanding grits and /or no sanding and applying coats within a specified time window so they can still chemically adhere to the previous layer...thats why this crap is so expensive...and every manufacturers system is slightly different...once you deviate from this formula to try to save time or money you're now doing a science experiment to learn by trial and error what you can get away with...you're trying to smooth out the original finish and remove all the crumbling oxidized paint so it doesnt continue to deteriorate under your new stuff but leave it with enough texture that the next layer will adhere...and then you need a fill prime over that you can fine sand with around 500 paper...but that primer needs to be something that wont attack the old paint and is compatible with the new stuff...talking with people behind the paint supply counter will help
 

MightyMats

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OP here is my advise, I worked in a custom shop for three years for what it is worth and spent a lot of time doing and learning paint from an experienced professional.

-400 grit paper is perfect if you want to paint over old body work. I would actually recommend you just use 320 and then 400 grit. Since you are painting over an existing base you only need to scratch the surface up good. Your intention shouldn't be to take it down to metal unless there is rust but now we are getting into cutting, welding, metal work, and body filler and I can't explain that on a forum. I would personally use 320 to cut that peel out and then a follow up with 400.

-Generally speaking the only time we ever went over 400 at the shop I worked at was when we were blending paint jobs. Make sure you use a block.

-The reason why you are seeing scratches is a combination of things. First you are not using primer. You need to shoot the substrate with epoxy primer at 400 grit. Also you might not be sanding out the 180 grit scratches enough. This is why I recommended you use 320 and 400. It may take more time... but it is more forgiving.

-Do everything by hand, do not use a machine if it is your first time. It is very easy to create waves in the surface with power/air tools. Do it by hand and go slow. 90 degrees you got that right.

-At 400 grit you will be fine in terms of the mechanical adhesion via sanding scratches assuming you have no contaminants on your substrate and use an epoxy sealer, period.

-when your car/panels are finally "paint ready" you will need to set everything up to get painted. Wipe everything down with an automotive paint prep degreaser. You can purchase it where you get your paint.

-I would recommend you use an epoxy sealer before you spray your color. Gray is usually standard. You will get better adhesion, potentially more uniform color, wear resistance, its just good to use an epoxy sealer.

-if it is your first time spraying I would recommend you stay away from metallic paints. Base/clear can be more forgiving than the oldschool style single stage. It is honestly a matter of preference what you use. But single stage will be less work to spray because you will not have to spray clear.

-You will get orange peel and your paint job won't be perfect if you are new at this. No level of sanding before you spray your color will fix orange peel. Orange peel is determined more by the quality of spray gun used rather than the amount of sanding. A high quality gun shoots the paint droplets out smaller in a finer mist. This being your first job I am sure you are not keen to spend over $500 on a professional Sata spray gun. So if you want it to be perfect, you will have to come back and knock out the peel with 600 grit and add a flow coat (single coat of clear).

My .02$ Hope this helps

For what it is worth, this is my 77 Jeep CJ7 I painted at the shop and did all the body work and prep myself. Paint came out perfect and I did everything I stated above. however I did not paint it myself. I had the pro at the shop shoot it because painting is not easy. I should note that the paint has not been sanded or buffed. That is with 400 grit sanding, epoxy primer, single stage paint followed up with a clear coat for more depth.

"Rudy" My CJ build

Edit: When you shoot epoxy primer on your car you should be ready to shoot your color on top. Epoxy primer can be used over the older paint and will adhere. If you need to fix dents and dings in your paint do it before you shoot epoxy. Epoxy primers do not like to be sanded and will gum up paper. They are used as sealers and are not intended to be heavy sanded. If you want to sand your primer to get a uniform surface you will need to shoot epoxy then shoot the car with a high build polyurethane primer. You can then sand and use your color on top of the poly primer, although I would again recommend shooting it again with epoxy. The stuff provides excellent adhesion and provides you with a uniform base color to lay your paint on top of.
 
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CBODY67

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What you might investigate is a local/regional automotive trade school. Where you can enroll and take only certain classes rather than the full number of courses . . . unless you want to take all of them. Sealers are wonderful things! Keeps all of the existing stuff encapsulated and hidden so they don't rear up to show themselves after the final color is on the metal.

Back in the old single-stage days, some of our body shop customers would primer the car, then mist on a black guide coat to sand off, then shoot the color when that process was done to their satisfaction. In order to get a slicker finish, they'd use USED red Scotchbrite pads (which started life as a 600-grit equivalent) for the final sand and buff activities.

As I recall, the "thousands-grit" paper was used for "finesse polishing" at the factory level, to fix blemishes and not have to do any repaint of the area. Remember, too, that the finer the grit, the LONGER it will take to make a difference in the area being sanded. These super-fine grits are also in the body shop supply areas, too, IF you might dessire to spend the time using them.

The other thing about modern painting is the HVLP (high volume low pressure) equipment. Compared to the prior spray guns, the HVLP guns will take some getting used to, as I understand it. But once you learn to use them, they work great. The lower pressure aspect reduces overspray by a large amount, whereas the old guns shot the paint and it bounced off the surface, by observation.

IF you desire to remove the old finish, there are some liquid paint strippers that work well and clean up with water. When using these strippers, DO lay some flattened cardboard boxes under the car to catch the drippings, so they can be later ecologically disposed of. BUT . . . these can increase the amount of work you're signing up to do, fwiw, although the results can be worth it.

So . . . go find a trade school and take some buddies along, too!

Just some thoughts,
CBODY67
 

thethee

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Starting with 180 is too course of a grit. Even going over with finer grits you probably still didn't get all the deep scratches out. 320-400 is about as course as you want to use unless you are priming or putting down a sealer.

I'm pretty sure this is what I did wrong. Tried sanding it again yesterday. Unfortunately when I got it somewhat smooth it revealed some deep scratches from an orbital sander from a previous owner so I had to sand it back even further. Laid on some primer and it already looks a lot better though. It won't be perfect but it's gonna look way better than it does now so I'm excited.

Kept thinking "damn, this is a big car" though.
 

tbm3fan

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As some have said the 180 start point was way to aggressive. The scratches it left are pretty deep and clearly you did not get to the bottom of them and now have them showing through the paint. If your intention WAS to repaint then start with 400 wet for solid colors in a crisscross pattern. One uses 600 wet for metallic.

Orange peel is a different aniimal as you have already laid down several layers of paint and need to knock down the high spots since the paint didn't flow out. When I have done that I start either at 800 or 1000 on a block wet sanding in crisscross. Check constantly by wiping down and viewing results. Stopping when I feel it is right.Then a 1500 clear coat disc on my electric version of the air vantage. Followed by 3000 and then 5000. Compounding after, with either my Makita or Flex equipment, that takes very little effort. I only shoot single stage on my cars with a 4 stage HLVP setup.
 
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