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Paint - Primer stage questions
http://classiccamaroclub.mfatw.com/viewtopic.php?f=9&t=1329		 Page 1 of 2
Author:  78 Camaro [Sun Sep 12, 2010 10:43 pm ]
Post subject:  Paint - Primer stage questions
Hey all,

Would appreciate your advice on this stage of the process please, this is where i am at:

Some repair areas were back to bare metal and painted with etch primer. Following this everything was painted with 3 coats of high build primer (Max Mayer 3011) (90% of the body had the original paint flatted back with wet n dry before primer). Black rattle can added ontop for a guide coat.

My questions start here... (pictures attached too)

1) I have flatted back the guide coat with 240 wet n dry and some areas have cut back to the underlying paint (red)... is this a problem? (will be be painted red anyways)

2) there was a white painted stripe on the car which has also in some areas been cut back to... is this a problem? (will be painted over with red)

3) one area has ben cut back to bare metal (size of a pea) ... do i need to etch, then prime?

4) some areas have been cut back quite far but there are is still some black from the guide coat there (speckles, quite light)... do i need to keep cutting back, even if the surrounding area will go back to the old paint, or do i add more primer to these areas? (is it an issue to paint over the guide coat?

Thanks for your help!

Ray

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Author:  silver back [Mon Sep 13, 2010 3:40 pm ]
Post subject:  Re: Paint - Primer stage questions
when flatting i find 800 wet and dry the best other wise you will see the scratches where you flatted,as for the parts that have gone through i would re prime as they can ring up or start to react and then you will start to get problems,as for bare metal parts again i would re prime,the black guide coat should be flatted back so you know you have got an even flat.it also depends what paint you are useing as what you can get away with,hope that is some help.
Author:  Rocky [Mon Sep 13, 2010 9:33 pm ]
Post subject:  Re: Paint - Primer stage questions
Re-prime as Silver back says until you get it flat, 600-800 would be better for wet flatting, I tend to dry sand as some primers are porous and you tend to get rust spots on bare metaled panels. I then use a non sand primer to get a perfect finish for top coat.
Author:  78 Camaro [Mon Sep 13, 2010 11:46 pm ]
Post subject:  Re: Paint - Primer stage questions
Thanks both for your advice.

I wanted to avoid repriming, but it looks like no choice! Would i be repriming the whole body i take it? (as there are slight high n low points in random places) kinda sucks that i got most of it nice and flat and have to redo :(

I was going with 240 wet and was then gonna follow it by 600 wet. Should i just skip to 600 wet? there's very little baremetal, either because it was etch primed before this primer, or it had existing paint already, but good heads up, would not have thought that!

Not thought of non sand primer, the system i have going on is: 2k etch for baremetal, then 2k high build primer, flat it, then 2k colour high gloss. Go a few spots left to look at, such as the body line in one place, so gota do that before repriming. nearly there :)

Cheers,

Ray
Author:  evilzee28 [Tue Sep 14, 2010 9:42 am ]
Post subject:  Re: Paint - Primer stage questions
Quote:
Hey all
My questions start here... (pictures attached too)

1) I have flatted back the guide coat with 240 wet n dry and some areas have cut back to the underlying paint (red)... is this a problem? (will be be painted red anyways)

2) there was a white painted stripe on the car which has also in some areas been cut back to... is this a problem? (will be painted over with red)

3) one area has ben cut back to bare metal (size of a pea) ... do i need to etch, then prime?

4) some areas have been cut back quite far but there are is still some black from the guide coat there (speckles, quite light)... do i need to keep cutting back, even if the surrounding area will go back to the old paint, or do i add more primer to these areas? (is it an issue to paint over the guide coat?

Thanks for your help!

Ray
Hi Ray, I wondered where you'd been hiding, being very busy obviously, some great progress made there.

Right a bit of help for you. Silverback & Rocky are spot on with what they've said. 240 grit is too coarse a finish to paint on top of, you need 600 or 800 for a good finish. I'm assuming that you're just going to "spot prime" the areas that you've gone through on & not primer the whole car again? You said that you were going to rub out the 240 grit marks with 600, well, best to do that now before you spot prime, as in doing so you might well go through the primer in places. Re guide coat it & make sure ALL of the guide coat has gone when rubbing out the 240 scratches, otherwise those 240 grit scratches will come back & bite you in the top coat. If you intend to primer the whole car then don't bother flatting out the primer that's on there with 600/800, just prime it & flat again with the right grade paper.

Where you've gone through to the red I'd re prime those areas, so that when your colour coats go on it'll be a uniform "primer base" for the colour. Likewise with the white stripe.

There's no need to etch the whole panel where the pea sized repair has hit the metal, I'd just spot etch it & prime/flat it out.

Guide coat is there for you to see what hasn't been rubbed out properly, always try to get it all rubbed out & then you're guaranteed to have a good base without imperfections to paint over. Painting over guide coat shouldn't be a problem, but best to get rid of it.

Rubbing the primer can be done wet or dry, the downside is that dry the paper tends to get clogged quicker, but wet, you run the risk of leaving water sediment on the fresh primer. If flatting wet make sure that it's totally dry after you've finished.

To be honest, it really depends on how much of the original colour is showing & how many spot primes you'd have to do to rectify that, as opposed to the extra cost & time involved in re priming the whole thing. A total reprime or non sand primer as Rocky suggested would be the ideal way to go, but obviously there's extra time/effort/cost involved. If there's not many "go throughs" to do then I'd spot prime it, if however, there are quite a few on each panel then a reprime is the answer. If you do decide to spot prime the repairs, remember that the overspray will stick to the rest of the paintwork, so you might either need to mask it out or just flat off any overspray afterwards.

Best of luck & keep thopse pics coming

Hope that helps a bit, cheers....Nige
Author:  Rocky [Tue Sep 14, 2010 9:48 pm ]
Post subject:  Re: Paint - Primer stage questions
You will have to work with whats best for you really as every painter has a different technique. I personally would hi build the whole panel again as spot repair can lead to a rippled panels unless you flat it out but with the extra overspray you might aswell do the whole panel but as I say its up to you what will work best, I normally get the panel flat enough and with enough coats of hi build that i dont go through but I still non sand or seal coat it to give it a better gloss hold out.
Author:  78 Camaro [Wed Sep 15, 2010 3:07 pm ]
Post subject:  Re: Paint - Primer stage questions
Hey guys,

Thanks for taking the time to reply. It's defintaley helped to get my head around the best thing. My change of tactic then is to give it another quick rub down using up the rest of the 240 wet and not worrying too much about break throughs as the shell may aswel get a respray. I have a large tin of paint left, makes sense to use it and avoid potential issues of spot repairs as you mentioned. Once reprimed, i will guide coat, hit it with 600 wet and hope there will be no break throughs. I am a bit worried about adhesion between guide coat spots so would rather cut back further to avoid any issues.

Couple of questions if you don't mind, is the flattening to get rid of panel imperfections or "human not spraying equally enough" imperfections? second question, is the primer supposed to be smooth as top coat paint would be? it has a slightly rough texture to it, which i though was due to it being a high solids filler paint and therefore it would naturally be rougher than topcoat.

I will let you know how i get on, i found a slight kink in the pass door at the bottom, while straightening, there was a crack, turns out if had been fillered, peeled up filler to find some live and kicking rust, so have to cut shape and weld, which has put me back a little bit now :(

Will post back on the w/end.

@ NIge... PM'd you the other week, not sure if you got it? Put loads of pics on the Project page too :)

Thanks!
Author:  Rocky [Wed Sep 15, 2010 8:58 pm ]
Post subject:  Re: Paint - Primer stage questions
Right you can get panel imperfections out with hi-build but takes some time its normally used to finish off filler work remove scratches etc and get out small ripples. If the gun isnt set up right or not painted well it can cause hi and low spots, you want a nice even coat, It wont be like a topcoat or clear it will be thicker so cause more orange peel effect but will depend on what gun you use what fluid tip and what air pressure you run.What gun are you using?
Author:  78 Camaro [Thu Sep 16, 2010 3:13 pm ]
Post subject:  Re: Paint - Primer stage questions
Hi Rocky,

Thanks, okay that makes some more sense, I'm using a Sealey 701G gravity fed gun. http://www.sealey.co.uk/PLPageBuilder.a ... ctid=10121
I'm being a bit naughty and using the same tip throughout the process (1.4mm)
PSI is set to 55, but only because when i press the trigger, it drops to 45PSI continuos. I am using 2 compressors joined by the hose and then into a Sealey water filter (i have pics i'll upload them as we like pics on this forums :) ) the etch primer came out beatuiful - flowed really well and was really smooth. The primer was a bit rough to the touch hence my maybe unecessary worries.

Another question that i thought of.... i am using a 10-12 inch sanding block on as many large panels as i can. Should i maybe only be using a small hand block? i thought that by using a larger block i'd get a more even finish?
Author:  silver back [Thu Sep 16, 2010 7:16 pm ]
Post subject:  Re: Paint - Primer stage questions
you say that the primer is a bit rough to touch in places it should be smooth as if you have rough areas when you come to flat and polish you can take the tops off and leave little white specs witc wont be good against red paint,as for blocking i use a nice peice of wood about the size of a 3m rubber block as i find you get a lovely even flat but like rocky says we all do thing slightly different hope you get on well.as for spray guns i use a devilvis gravity fed with 1.5 air cap.
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