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How to: Prep for paint, from bare metal or respray

General Discussion. Make yourself at home...read, ask and answer!

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PostPosted: Wed May 04, 2011 9:57 am
I see these questions come up a lot, so I thought it might be a good idea to put all the answers into one thread. :)
Let’s try to keep the questions to a minimum but suggestions, additions or corrections should be posted here. This will keep the thread clean and hopefully we can make it into a sticky.

These procedures do not apply to a complete restoration. A complete restoration should be examined carefully before repairs are carried out, and in most cases media blasting or other mechanical/chemical stripping will be necessary.

1) First, determine if the car or panel needs to be completely refinished, or if it can be resprayed.
If you have already determined which route you are going to take, skip to Step 2.
If you are performing a complete paint job or basic restoration, it is best to strip the vehicle in most cases.
If the paint job is relatively new, and is only 1 layer (original paint, or stripped and repainted), sometimes it can be sanded and resprayed or primed/sealed and resprayed after proper prep. I still feel the best and longest lasting paint jobs are complete refinishing from bare metal or factory primer on up.

2) After you have determined what level of paint job you want to perform, now is the time to prep the body.
Before sanding anything, wash the vehicle with soapy water, preferably warm water. Use Dawn dish soap or a high quality non-wax auto shampoo.
Pay special attention to wheel wells, gaps between panels, cowls or anyplace dirt can hide. Often nooks and crannies are overlooked and dirt/grease can work its way up onto the panel or paint will lift around the edges of the panel.
Be very thorough with your washing, this is one of the most important steps!

3) Remove trim, door handles, and mask off openings or headlight/tail light cutouts.
The more trim, handles and other parts you remove from the vehicle - the cleaner and longer lasting the paint job. If you mask off handles and trim, the edges of the paint or clear can lift in time. Once the edges have started to lift, it’s a matter of time before chipping and peeling happens in these areas. Masking off these parts can be done, but don't plan on a very long lasting finish.

4) Wipe the car or panel down with Wax and Grease remover. The most efficient way is to load your W & G remover into a solvent sprayer. This makes it easy to spray your panel with solvent and wipe it up with a fresh shop towel.
Another way is to soak one paper shop towel with solvent, wipe the panel, and dry it with another new shop towel while the panel is still wet. This way you will not be spreading contaminants and are sure to remove them.
It is very important not to use only one solvent soaked paper shop towel. Do not use red shop rags or other cloth rags that can contain contaminants. A 2nd dry paper shop towel should be used. Wiping in 1 direction also makes a difference in cleanliness in the final passes.
Let the solvents flash (dry) for at least 20-30 minutes before priming or painting any panel! Solvent pop or other adhesion issues can occur if proper flash time is not followed.
The W & G remover will generally remove most automotive type waxes, grease, motor oil, petroleum products, and most silicones.
Some painters follow W & G remover with an organic solvent like glass cleaner or isopropyl (rubbing) alcohol. This removes contaminants such as finger prints, bugs, and certain oils.
Alcohol or glass cleaner (ammonia + water) is for organics - tree sap, bird poop, bugs, finger oil, natural oils in car waxes such as Zymol.

5) Sand the body.
If prepping bare metal, P80 grit paper on a DA sander works great. Blow off the panel and wipe it down (as outlined above) before priming. Then you can apply 2 coats of epoxy primer, followed by 2-3 coats of high build primer. If prepping existing paint or primer, P180 on a DA works well, followed by 2-3 coats of high build primer. If you are planning on sealing the primer or paint, P320 grit is usually adequate.
Personally, I don't use a sealer and just final sand high build primer before color. Sealer is added insurance if you are painting over an unknown material or layers of primer/filler that has been feathered and is showing through.

6) Apply your primer or paint.
Leave the area and come back to inspect your work later. Otherwise you will just be poisoning yourself in the fumes and temped to pick at your work before its ready.

Some of these steps may seem like overkill, however the extra time taken here can save you $100's or 1000’s in wasted materials if you have a contamination or adhesion issue.
:goodjob:

Feel free to add anything you see fit! I will continue to edit this post with new info.
-Bobby

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PostPosted: Wed May 04, 2011 8:04 pm
It was my understanding that a final wipedown using alcohol was to cut dust. I thought (generally) the W&G remover will remove the fingerprints and ect.

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PostPosted: Wed May 04, 2011 8:08 pm
The alcohol will also help with static removal and organic oils. It also helps remove Armor All.

W&G remover will not remove all contaminants...................
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PostPosted: Wed May 04, 2011 8:39 pm
Exactly. The W & G remover will generally remove most carnauba types waxes, grease, motor oil, petroleum products, most silicones. Alcohol or glass cleaner (ammonia + water) is for organics - tree sap, bird poop, bugs, finger oil, natural oils in car waxes.
Will post pics next time I have a metal project to paint, should be a few weeks.

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PostPosted: Wed May 04, 2011 8:58 pm
vwbobby wrote:Exactly. The W & G remover will generally remove most carnauba types waxes, grease, motor oil, petroleum products, most silicones. Alcohol or glass cleaner (ammonia + water) is for organics - tree sap, bird poop, bugs, finger oil, natural oils in car waxes.
Will post pics next time I have a metal project to paint, should be a few weeks.
I think you have a few pics of a hood repair or 2, ODG? :)

Ya learn something new every day! If you are mixing up things to spray as a cleaner (alcohol or ammonia with water), I think it'd be fair to say one should use distilled water, just in case.

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PostPosted: Thu May 05, 2011 7:09 am
,"I think you have a few pics of a hood repair or 2, ODG? "

Yes I do,,,but I think most of the guys on here have seen it.

If I am working on a body panel in my shop by myself and strip a panel down to bare metal, I wipe it off with W&G remover then prime.
I dont give it time to get contaminants on it. (I dont let it set over night) I prime it right then.
You dont want to leave a bare metal panel exposed to the atmosphere here in the south close to the coast. It will start to rust very fast.
"The number of parasites in the USA has now eclipsed the number of productive members of society"


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PostPosted: Thu May 19, 2011 3:52 pm
Something else I just remembered:

When washing the car, or wet sanding don't forget to spend a good amount of time blowing out every nook and cranny with compressed air afterward. I usually spend a good 10-15 minutes going over the entire car at 90PSI with a blow gun and trying to clear out every last bit if water or junk that might be hiding in there. You don't find it now, there's a chance your spray gun will find it later (!)

-Chris



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PostPosted: Mon Jul 18, 2011 3:21 pm
Let the solvents flash (dry) for at least 20-30 minutes before priming or painting any panel! Solvent pop or other adhesion issues can occur if proper flash time is not followed.
Some painters follow W & G remover with an organic solvent like glass cleaner or isopropyl (rubbing) alcohol.


after wiping it with solvents do you wait for 20-30 before wiping it down with alcohol.?

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PostPosted: Wed Aug 24, 2011 5:49 pm
No need to wait. Once you've wiped the panel off, the remaining solvent should flash off very quickly (after being wiped with a dry towel). Then you can wipe it down with alcohol, if you wish.



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PostPosted: Wed Aug 24, 2011 6:16 pm
SPI waterborne cleaner does a better job than plain alcohol, and reasonable priced too.
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