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Old 09-16-2004, 06:16 PM
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Newbie needs help with painting....

I've been lurking this board now for a long while and I have to say, that I have never seen SO MUCH info in a single place! This place really is great. And I hope I can get some help with some questions I have. I have searched and although there is a ton of info out there, it is a little daunting filtering through it.

Before I ask, this is some info on the rig and paint:

This is an off-road 4x4 that I've swapped an engine into (along with the tranny, t-case, axles, springs..... basically everything is from another manufacturer except for the frame and body). Although it is for off-road, it is also my daily driver which is why I would like to do a "nice" paint job.

I will strip the paint this weekend using both chemical and media blast. I will then apply POR-15 on all exposed areas and apply the primer that POR has suggested.
On top of that, I will apply a DuPont base colour, and follow that with a clear I have from another manufactuer. This clear (I can't remember the manufacturer) will adhere to the DuPont. I got a sample of it for free from another fellow chemist so I would like to use it.

I will be using an HVLP gun and doing this all in an enclosed area.

Now the questions:

(1) Once I apply the POR primer, how long should I wait for it to dry before I apply the colour coat?

(2) How many coats of colour?

(3) What grit should I sand the primer and colour coats with?

I think that's it! Other than my questions, how does my setup sound? I don't plan on wet sanding/buffing the final clear just because I'm afraid of buffing to far through the clear and ruining the paint.

Thanks for your help

Cheers,
Steve

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Old 09-16-2004, 07:38 PM
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Short n Sweet

Hi-

I like the short&sweet Q&A: Here's what I'd do, others will have different opinions. I've shot POR15, and I've covered it with Dupont Chroma System, and I've covered POR15 with Chroma Premier (both 2-stage). Here goes:

(I think the POR15 "primer" is a waste, I've never had trouble with other primers sticking to the POR15)

1) Don't know. I'd wait 48-hours after painting the POR15, but I don't know about their primer. I'd be worried their primer is porous, sucking-in your expensive Dupont paint. Personally, I'd cover the POR15 with Chroma Premier sealer that's been "Value-Shaded" (Dupont jargon for pre-colored). You'll use less paint. If you haven't bought the POR15 yet, you can try the Dupont Epoxy DTM Primer-Sealer (DTM=Direct to Metal). If you haven't sprayed POR15 before, it sucks. Wicked-noxious (full respirator), and I always have trouble with thinned-POR15 peeling off the metal like a sheet of plastic film. Brushed-on POR15 seems pretty bullet-proof.

2) Depends on how you lay-down with an HVLP. Dupont recommends 2-3 coats. I do 7-or-so, but that's usually because I want the deepest color I can get. If you value-shade before the paint, you can probably get away with 2-3 medium-wet coats.

3) Sand the primer? Are you talking about post-POR15, pre-sealer?? You can't sand POR15 at all. And you never want to sand sealer. If you're talking about something like Dupont's Prime-n-Seal, I'd use 320(wet), but you should finish with a non-sanded seal-coat. Never, ever, even on a dare, sand the Chroma base-color. Sanding it takes off the top "rough" coat, and the clear won't adhere. If you're talking about single-stage Color, then I wouldn't use anything more agressive than 1000, Dupont will tell you 1500. Start with 1500, if that doesn't do it, hit it with 1200, then 1000. 1000 will (for the most-part) buff-out, but 600 won't (trust me!).

Lastly- don't worry about sanding the clear. It's not like you're trying to descale-rust here, you're just lightly (1500-2000grit) rubbing it, almost the grit of compound. And, $100 says you'll have more than 1 run to contend with, unless you're painting in a temperature and airflow-controlled booth with enough lighting to play a night football game. The color is a breeze, the clear isn't. Color goes on somewhere around 1-3mils thick per coat, the clear is closer to 7-8mils per coat. Do what the rest of us do, lay down 3-or-4 coats of clear when you're only planning on 2, then sand it down those 2-coats.

One final note, if you are skilled (lucky) enough to actually lay down clear without runs, don't touch ANY part with sandpaper, as you'll never be able to match the texture from the sanded (mirror) finish to the factory (orange-peel-texture) you'll get from un-sanded spraying.

I attached a picture for those of you who don't believe a buffer can make up for a whole bunch of mistakes. What you'll see is a tailgate with 4-coats of clear, purposesly sanded with 1200 about 2-days after the clear was shot. The right-side shows what it looks like buffed (and, if you're wondering what those "spots" are in the buffed paint, it's actually the reflection of my garage's ceiling, those spots are the un-finished spackle of the sheetrock!

Good luck, send pictures when you're done!

-Kustomizer
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Old 09-17-2004, 07:18 AM
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(just my $.02 added here!) By all means buff your clear- that is what they are intended for- to give a glossy smooth clear reflection... use really fine grits (as suggested already) and take your time... nothing makes a slick paint job like a well buffed clear!!! (and adds to the durability)
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Old 09-17-2004, 11:21 AM
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Wow, thanks for all that info! The POR won't be sprayed on, so I do plan on brushing it on. "Apparently" it has a self-levelling agent and I should be OK. Whatever the case, it'll have to work.

And thanks for the POR primer tip. I'm just going to buy the Dupont Primers you suggested and go from there.

The only other question I guess I have is in regards to the clear. What grit would you suggest I wet sand with, and then what about the buffing compounds?

I saw a show once where they were explaining the art of buffing clear, and I remember them saying that you should never use the buffer around sharp edges b/c you could burn through. But if no buffer, then what? Hand buff? Random orbital? Just need some advice Thanks again!

Cheers,
Steve
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Old 09-17-2004, 12:11 PM
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Buffing

Hi-

Check out another thread I'm in about buffing:
http://hotrodders.com/forums/showthr...289#post334289

You'll see what I use.

As far as grit to use on the clear, I told you above... (2000)/1500/1200.

-Kustomizer

Oh, and the part about burn-through when buffing the clear can be an issue for people who only lay-down the "recommended" 2-coats. That's why we customizers lay down 4-5. Also, the 3M hookit pads listed in that other thread are pretty forgiving, and you've got to have hands of rock if you're putting enough pressure on those foam pads (or not moving the buffer) to do that much damage. Buffing ain't 'grinding', it's more like passing a feather-duster over a fine dining-room table.

-Kustomizer
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Old 09-18-2004, 11:15 AM
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Thanks!

Thanks again. That buffing thread gave me some good guidelines on what I need to pick up before I start painting. After reading it though, I saw something interesting. You mentioned something about buffing on a semi-hard clear? And that clear should be put on before 24 hrs of base colour? Is that right? Once I spray on the last coat of colour, how long would I wait to clear it?
And the buffing of the clear, once the final coat has gone on, how long should I wait (or not wait) to buff? Thanks again

Cheers,
Steve
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Old 09-18-2004, 11:29 AM
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Re: Thanks!

[QUOTE]Originally posted by Hemogoblin
[B]Thanks again. That buffing thread gave me some good guidelines on what I need to pick up before I start painting. After reading it though, I saw something interesting. You mentioned something about buffing on a semi-hard clear? And that clear should be put on before 24 hrs of base colour?
**********************************************
Not so, You must get tech sheet as every base is different including the different bases Dupont makes. Times range from 6 hours to 27 hours depending on base. This is not an area you guess at.
bwk

And the buffing of the clear, once the final coat has gone on, how long should I wait (or not wait) to buff? Thanks again
************************************************
Here again if its a HP resin some can be buffed in hour others 4hours or over night. Dupont makes about 20+ different clears and all are different. Wait to long and you will think your buffing cement. Need tech sheet!
bwk
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Old 09-19-2004, 06:29 PM
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Wait period

BarryK is correct on most parts...

Every base/topcoat is different (obviously), and the times will vary based on temperature, airflow, and whether you're baking it. However, most anything you'd use in a non-production facillity (like Chroma Premier, NOT "ultra productive") generally has the <24-hour mark for recommended clearcoat application after paint. But, certainly read the can before you apply it, and be prepared to shoot clear within around 12-hours from your basecoat. You can also buy additives to extend those times, and there's always adhesion promoter if you waited too long (adhesion promotor affects the DOI, distinctness of image... if you're looking for the "factory" non-deep look, use adhesion promoter or flexible additive. If you're looking for the deepest look, stay away from them).

And, either BarryK is a professional painter in a professional facillity, or he's braver than I... I've screwed up too many clearcoats trying to buff too early, when it's soft and can move around a lot. He's 100% correct, after 24-hours the clear is rock-hard. But, that's not a bad thing (unless you've made lots of runs/sags you need to repair).

If you sag/run a panel, it'll take days for you to sand/buff them to perfection if you wait more than 24-hours. Someone who knows what they're doing with a buffer can repair it in an hour, if it's still soft. Someone who doesn't know what they're doing with a buffer will mess up their new clear coat, requiring a sandblaster or chemical stripper.

I find that it IS a miserably-long job to sand-out sags or runs in hard clearcoat. But, the harder something is, the deeper the shine after buffing, and I don't run the risk of having to reshoot. Since I average shooting less than 3-4 cars a year, I find sanding down the hard clear a labor of love.

Good luck,

-Kustomizer
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Old 09-19-2004, 07:25 PM
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Clear buffing times.
I should have been a little more precise in my response.
The hyper clears of course can be buffed depending on type and temp in 30 minutes to 4 hours of course this would best apply to a production type shop and us do-it-yourselves can easily wait over night to buff. (and should)
Most clears that are air dried (not baked) will buff good from next day to three days fairly well. A lot of the clears will start buffing very hard after 3rd or 4th day and some after about 5 days forget it. Tech sheets here can save a lot of sweat and tears for sure for the do-it-yourselfer.
A lot of factors go into deciding how a clear buffs, such as type of Isocyanate, resin of the clear and the final hardness designed into the clear. Rated by pencil hardness.
On the opposite side of this some clears will not buff at all before 4-5 days, although these are not normal clears used in automotive refinishing they do find their way in this market sometimes.
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Old 09-21-2004, 06:17 AM
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Barryk and all the rest of the reply are good info, but few told you about isocyanate's, you spoke of an enclosed area I hope you have some kind of ventilation, respirator's will not remove isocyanate's they will kill you or at least wreck your nervous system , please check this out I speak from experience. Doc.
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Old 09-21-2004, 01:45 PM
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Quote:
Originally posted by docs57
Barryk and all the rest of the reply are good info, but few told you about isocyanate's, you spoke of an enclosed area I hope you have some kind of ventilation, respirator's will not remove isocyanate's they will kill you or at least wreck your nervous system , please check this out I speak from experience. Doc.
*********************************************
How right you are! Sometimes we discuss this stuff like it s a low carb beer and the safety issue is overlooked.
The stuff you can smell is not the killer, it the stuff you can't smell you need to be worried about.
BWK
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Old 09-23-2004, 01:36 PM
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Thanks for all the help guys. I was going to have my media blaster (after he has epoxy primed it too) paint the rig but $$$ is tight and I have everything already except the base colour paint. Soooo, I'm likely doing it myself. We'll see how it turns out

I won't be painting "exactly" in a closed space. More like outside in a screen house that I fabbed up. Basically allows for fresh air to circulate but no bugs, pollen, etc. Should be sweet, and I'll also have a fan at the door to pull some overspray out.

Wish me luck!

Cheers,
Steve
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Old 07-07-2010, 08:59 AM
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just a side note and tip, if you get runs and sags in your clear coat best way i've found to level them off is with a small piece of paint stick with 1200 grit paper and a razor blade, you use the razor blade to take the top off the run, the with your paint stick and paper you concentrate soley on the run, keeping it level and flat the run will sand down and as it does so, go to 1500, and finally to 2000, when you wet sand your project you'll be able to see any imperfections in the clear/paint/ or runs that are still present they will be shiny compared to your flat area that has been sanded smoothly. be sure not to buff and polish in the direct sun it'll bake on to the paint and make it hard to work with also.
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