Basic Painting Questions

[GaryDG]

I am '83 911 guards red.

I have a couple areas on this car (front spoiler) and a trunk lid on a different car that need to be repainted so I am planning on getting a HVLP setup to tackle these jobs.

On the 911, I understand this car was originally painted single stage - meaning no clear coat. When small areas of the car are resprayed, like the spoiler, should it single stage as originally painted or is a cc put down as well?

I know it is a matter of how much product is put down but approximately how many square feet of painting area is covered by one quart of a) base and b) clear coat?

Do most people go with BASF Glasurit for base or are other products equally good?

Lastly, I would think it is best to go with the same paint manufacturer for primer, base and clear coat, is that correct? Based on the thread "Epoxy Primer" by emo, 962 says yes.

Thanks,

[962porsche]

1st
you will need every thing HVLP not just a gun or the gun will not work as it should .
so that's hose , cupplers, fittings , very thing right from the air supply to the tip of the gun if any part is not hvlp than the gun will not get the needed volume of air .

2nd.
if the car is in single stage then most of the time it's best to do every thing that way .
one reason is the way a single stage finish looks the other reason is over time they will not fade the same . it's not to say base clear does not fade because it does it just looks deferent when it does .

3rd.
there is no real answer for how much coverage you get out of a sprayable product .
it has to do with so many things like if it's a high solid , medium solid or low solid color .
than it has to do with what tints maybe in the mix that makes up a color . some tints are very opapue and if there are many of then in the mix you will not the same coverage as you would with out them .

4th.
many people use BASF (glasurit ) because it's what the OE finish is on porsche's .
it's also used on every high end car built like FERRARI , BMW , BENZ, MAYBACH , LAMBORGHINI , ROLLS , BENTLEY , i could keep going but you get my point .
so is it the best ? for me it is the reason is i know the colors will match when i paint that type of car i listed . i tried many other paint lines and found that BASF products work best for me .
but it's more than just what your putting in your gun that makes a paint line good .
all paint lines will work if you go by what the TDS tells you to do .
documentation has a lot to do with if a paint line is also any good . if they have no real color chips and leave it up to the end user to do there own spray out to see of a color will match it's a costly thing to leave up to a shop or the end user .
there is also the fact about how many variants they offer for a color code . if they only offer you one to pick from and it's not a match your left to tint the color your self .

5th
yes you should pick a paint line and stay with that paint line from your under coats to your top coats .
if you don't you could run into a product that is not compatible with some else you are useing .
when youe looking at the end cost on the paint line you pick one thing you will want to look at is the same products like hardeners and reducers used in all there sprayables .
with BASF you will use the same reducer in every thing also many of there hardeners are used across the product line .

[GaryDG]

932

Thanks for that info!

So just a clarification on the stuff other than the HVLP gun itself. I was planning to use my large upright compressor, which should have adequate volume/pressure. It has separate gauges showing tank pressure and output pressure (which is controllable).

I also read that the pressure at the gun may be different than what is shown at the compressor (output side) due to lost pressure from the line & connectors. I believe I read people mentioning that they slipped in a pressure gauge just before the gun to insure that pressure at the gun is correct. Is that your recommendation as well?

I also have question about approach.

I've read and understand several approaches for fixing scratches and paint chips but not in the context of spraying an entire area. Now, the picture below isn't the best, and the picture looks worse than the spoiler is because I am working on other aspects of the car and it is very dirty.

So, I will remove the spoiler, then begin the sanding process. Since after sanding, they'll be a couple small spots of bare metal, and the pits (from the paint chips and scratches) will remain. Is it appropriate to go with a primer in the areas of bare metal and pits (following the approach you just recommended for emo993's thread "Epoxy Primer") or primer the whole thing or?

I am assuming I will find the rest of the paint in good shape and so, if I don't primer the whole piece I can just spray over the existing sanded paint.

Thanks



Gary

[962porsche]

lets 1st start with your air system . yes you want a regulator ate the gun .
most gun makers want your pressure at the gun to be 25 to 35 LBS .
because the fittings , cupplers , air hose and regulators all have to be HVLP and it could cost you a crap load of money to change every thing over to HVLP you may want to look into what is called HVLP compliant gun .

from the looks of the panel you will want to strip the top coat off until you sand out all the chips and scratches .
start with 80 grit on a DA palm sander .
after you have the top coat stripped off and the chips /scratches sanded out even if you have to strip it down more than just removing the top coat you then want to change your sanding grit to 180 or 220 paper .
resand every thing you just sanded with the 80 grit .
at this point you will have many bare metal areas so you will want to spray one at most two coats of a quality E-primer over the bare metal .
if you have any body work to do with a body filler you can do it right over the E-primer just sand it with a red pad 1st or a light sanding with some 220 or 180 for the body filler to bite into .
once your all set with your work and your ready for a filler primer spray 3 to 4 coats of a filler primer .
once it dries sand it with 320 to 500 grit paper wet of dry and if you have some of the OE finish still on the panel you sand that with the same grit wet or dry .
you do not have to prime over the finish that is no the panel now . your just wasting material to do so . primers don't make paint stick any better so if there is noting wrong with the finish on your car you can spray your top coats over it .
once you panel is all sanded and ready for painting blow it off with a blow gun wipe it down with some pre paint cleaner then tack it off with a tack rag then mix your paint and spray .
if you brake thru when your sanding the part for paint to any bare metal you should spot seal the areas before you top coat .
many primers you can also mix as sealers . this is what i was talking about when you want to look at a paint system that one product will do more than one thing of you can use for deferent products .

[GaryDG]

Thanks again 962

I will check out HVLP compliant guns.

Can you clarify a few points you made in your last post:

You wrote

from the looks of the panel you will want to strip the top coat off until you sand out all the chips and scratches .
start with 80 grit on a DA palm sander .
after you have the top coat stripped off and the chips /scratches sanded out even if you have to strip it down more than just removing the top coat you then want to change your sanding grit to 180 or 220 paper .

I assume the 180 /220 sanding is done with the DA as well.

resand every thing you just sanded with the 80 grit .

What is the reason behind going back with an 80 grit after doing 180/220?
Also is the 80 grit done DA?

at this point you will have many bare metal areas so you will want to spray one at most two coats of a quality E-primer over the bare metal .
if you have any body work to do with a body filler you can do it right over the E-primer just sand it with a red pad

what is a "red pad"? The Scotch abrasive pad?

1st or a light sanding with some 220 or 180 for the body filler to bite into .

Is the 220/180 sanding done DA?

once your all set with your work and your ready for a filler primer spray 3 to 4 coats of a filler primer .
once it dries sand it with 320 to 500 grit paper wet of dry

is the 320 - 500 done by hand, with a block block sander?

and if you have some of the OE finish still on the panel you sand that with the same grit wet or dry .
you do not have to prime over the finish that is no the panel now . your just wasting material to do so . primers don't make paint stick any better so if there is noting wrong with the finish on your car you can spray your top coats over it .
once you panel is all sanded and ready for painting blow it off with a blow gun wipe it down with some pre paint cleaner then tack it off with a tack rag then mix your paint and spray .
if you brake thru when your sanding the part for paint to any bare metal you should spot seal the areas before you top coat .

When you refer to "spot seal", you mean EPrimer, followed by filler primer, but just in the area that became bare, correct?

[962porsche]

yes change the da paper to 220 or 180 and keep sanding with the DA . the reason is 80 grit will take the top coat off quick but you can't prime over 80 grit or you will see the DA sanding marks .

you just resanding the 80 grit with the 160 or 220 for the reason i just stated . you don't want to prime over 80 grit scratchs .
so 1st sand with the 80 grit on the DA to just remove the top coat and sand out the biger chips and scratches then again change the paper to 180 or 220 and again DA sand the same area . again to give your self a better finish on the panel to spray primer on .

a red pad is just a scotch - brite sanding pad . but scotch - brite is 3M's brand name for the pads . other CO's also make sanding pads like norton they call them bear-tex pads .
so they just get called red pads .
the color of the sanding pads tells you what grit they are . they have them in white , yellow , gray , red and green .
the red is the grit you would use to scuff up a E-primer .

i would do it by hand . to block sand some thing that is that curved would be a PITA and you may just make a mess of it .
when you sand by hand keep your 4 fingers together and nice and flat on the panel and hold the sand paper pinched between your thumb and undex finger . do not sand with the palm of your hand . if you do your work will come out wavy .

a sealer is just that . it's kind of a over reduced primer but it's a product that is made to do things like give the top coat some thing to bite into . it also gives a smooth surface to help not have any of the tops coat sink in and maybe delam later on in the cars life .
some filler primers can be mixed as a sealer also some e-primers can be like RM's EP primer can also be mixed as a sealer called polyuroxy .
this is what i was talking about when you look at a paint system you want to look at the hole system to see what products can cross over from one thing or use to another .
the EP primer you can use as a straight epoxy primer onyour bare metal then later on you can mix it as a sealer .
the BASF RM line of finishes are every good quality many or the products they offer are the same as the BASF glasurit line and a little lower in cost .
like the reducer it's the same as the glasurit but it's a little cheaper in cost . you can use it in your glasurit product line in place of the glasurit reducer . it's exactly the same product just the can it comes in is deferent .

[GaryDG]

Thanks again 962!

Very helpful. I have seen several YouTube painting videos, read a lot of threads, and now with your help, have now reached a point where the information I am reading and seeing make logical sense.

I will study the paint systems, there's a place close that sells BASF products, I can use them as a resource and the BASF webiste itself.

One last question on a different paint job.

Let's say the spoiler we talked about above was damaged beyond repair and I bought a new one off eBay or wherever, that was in great shape, no scratches or dings, but it was a different color, say gold.

Based on what you have said and I have read, I would sand the entire surface using 180/220 then proceed to the 400-500 grit level. Does one need to apply any kind of "blocker" or primer to go over the old color before spraying on the base coats to prevent the old color from bleeding through?

Gary

[GaryDG]

962
I think the answer to my last question is similar to your answer to Don G's thread Clear Coat Failing. This other paint job I refer to above does have clear coat on it, so it needs to be removed like Don G's. Since after that we'respaying with filler primer, then sanding , then we apply the base, then the CC. Is thatcorrect? If itiscorrect then am left with the question will the old paint color bleed through to the new paint color? I would suspect it wouldnt since there'saprimer coat over the entire area.

I need to get on with my study of paint systems as you suggest, but maybe the trick here is to mix the filler primer with a sealer? Just guessing.

[962porsche]

if your replacing a panel with a panel that is in good shape and the finish is good all you would need to do is wipe it down with a pre body work cleaner like RM's 900 then sand it with 320 to 500 grit spray a coat of sealer and top coat . there is no reason to have to prime a part if it's good shape .
your adding more mills of product that is not needed and wasting money and time .

[GaryDG]

962

The approach on the trunk lid, or any other panel without damage makes sense, thank you!

I thought I had exhausted my questions but I find I have another. I have attached a picture of the underside of the existing trunk lid. You can see that it's structure consists of two layers of metal. I understand the top layer should be dealt with as you describe in your earlier post (RM900, sand, sealer, base), but the bottom layer is inaccessible in some areas for sanding. Since the bottom level would have been washed, dried, cleaned with RM900 or the equivalent, and sanded where accessible, that is the best that should be done, prior to applying product(sealer, base), is that correct?

[962porsche]

as you can see the shell is not paint with the same amount of care as they do to the top sides .
all you have to do is wipe it down with pre body work cleaner (900) scuff it with a red pad blow it of real good then wipe it down with a pre paint cleaner like like RM's 901 . now you can use the 900 also for that but let it sit for about 15 to 30 minutes before you apply any sprayable's (sealer or top coat) over it . you do that because pre body work cleaners have a longer flash off time and you don't want to trap any solvents under the sealer or top coats .
then tack the panel off and spray your sealer than top coat .

you don't have to go to nuts sanding and painting under or between the two parts of the panel they don't then they paint the undersides of things . hell most cars don't use a top coats at all on parts like that what your seeing is really a sealer not a top coat finish . they call them under hood colors .
the over spray from when you paint the under side will just blow in the areas like it is now and cover the red if your doing a color change .
then it looks like there should be a trunk liner that goes in the under side of the panel ?
so if you do miss a little spot who's to know .