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Old 01-23-2005, 12:16 PM
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Time between primer and paint?

What kind of flash or drying time is acceptable between the primer sealer and paint? Reading threads below, it sounds like you can run into trouble with shrinkage etc. if it hasn't cured, but you watch all the shows on tv and it's nonstop spraying till it's done " to meet the high drama deadline" that they put into everyone of those shows. My car will soon be going to a paint shop for a second coat of high build, final block sand, shot of sealer, then some color. The guy doing it says he would like to let it sit for a week before he starts painting.I don't have a problem with that, but don't know for sure. Jim

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Old 01-23-2005, 12:30 PM
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First of all, if he is using quality products there is no need for a sealer, that only adds cost, texture, and labor. If the panels are completly primed in a quality urethane primer there is NO NEED what so ever for sealer prior to paint.

As far as how long you would wait, you didn't clairify WHAT you want to wait on. The primer after sanding "can" wait to be painted about as long as you want (check the tech sheets). The sealer (if your paint insists on using it) is a whole different story, it has a "window" it needs to be recoated it or it will need to be sanded. The tech sheet for the product will say, it could be 2, 6, 24, or longer depending on the brand and part number.
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Old 01-23-2005, 05:17 PM
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letting your primer set for a while wont hurt anything. your painter probably just wants to make sure all the solvents are good and gone. as for sealer, its not necessary and as brian said you should read the tech sheet. most that i have seen have a wait of about an hour then you shoot the base. i am a firm believer in sealer. i think it greatly helps the adhesion of the basecoat to the primer and in mettalic finishes it reduces any sanding scratches but that really depends on what primer was finally blocked with. i personally dont shoot basecoat on anything without a sealer but to each his own. as i said its not necessary.
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Old 01-25-2005, 12:26 AM
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As always, Rule #1: Read the 'P' sheets for the products you are using!
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Old 01-30-2005, 10:56 AM
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I only use sealer if I am shooting over existing paint.
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Old 01-31-2005, 11:22 AM
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I may get "dissagreed" on this but I like to let my urethane primer dry for a min of 3 days before I sand and paint.
I seem to get less "dye back" in the future.
I know most people don't wait that long and have no problems, but for me I get better long term results waiting.
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Old 02-01-2005, 01:32 AM
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I would agree with mrcleanr6 using sealer under base coat especially high metallics like silver and golds. even wet sanding your primer with 800 before painting can still show sand scrstches later after clear coating. I use a transparent sealer works good on spot jobs too. I have'nt had any dye back problems using sealer either.
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Old 02-01-2005, 09:35 PM
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What you're seeing on tv is the application of a wet on wet sealer that is designed for fast use. Some of these actually must be coated while in the wet stage, a good example is Sikken's color build I let it set overnight one time and sprayed the next day only to have it wrinkle- not happy I had exceeded the window on this new to me product. Sealers offer a couple of functions, a color base to help paint coverage, a solvent barrier to prevent solvents from being absorbed by the undercoats, and an adhesive coating for the topcoats to stick. They aren't needed in every applications-most quality urethane and epoxy based surfacer primers can be painted directly with excellent results. And as Martinsr mentioned they do add texture to your paintjob. The more coats of applied product the more distorted your perfected surface will be when the spraying is done IMO. Even basecoat will become rough if many coats are applied. I try to avoid the use of sealer whenever possible on quality jobs. High reflection fine metalic silver is an example of a color you wouldn't want to use sealer with IMO, the fine metalics must go on perfectly smooth because them mimic and show the exact surface texture that they are sprayed over so skip the sealer IMO and make sure the car's surface is prepped really wll before the paint is applied. I like to let my primers dry for a week or more is better whether it's epoxy, urethane, or polyester they all cure more when they set awhile-the difference in the amount of effort needed to sand them supports this. JMO's Bob
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Old 02-01-2005, 10:43 PM
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As far as I am concerned sealer is to be used when you have multiple substrates, period. If you have an original paint over the panel and a primer spot over a repair. That is a time for sealer. If you have a primed fender, and a hood on a compete where the rest of the car is a nice paint that has been sanded, that would be a time for sealer.

If you were painting a few panels all in a 2K primer that has been sanded with the recommended grit, just paint it. If it is OEM or a 2K paint that has good integrity, sand it and paint it.

I have not used sealer on completly primed panels in years. One of my "test beds" is my sister- in - laws 65 Mustang daily driver. I did it in S-W bc/cc 10 years ago. Urethane primer sanded with 400 and painted. It has seen maybe a total of one year in a garage, it sits out in the weather every day. It has vertually zero shrinkage, still looks as brilliantly shiny as the day I finished it.

Quote:
Originally posted by jcclark
I may get "dissagreed" on this but I like to let my urethane primer dry for a min of 3 days before I sand and paint.
I seem to get less "dye back" in the future.
I know most people don't wait that long and have no problems, but for me I get better long term results waiting.
Your procedure sure as heck isn't going to hurt anything. If you have the time to wait, by all means do. However, some of the "die back" problems are surely related to trapped solvents. So if all the products applied didn't retain solvent by the way of poor atomization, too much applied at once, insufficient flash times, incorrect solvent choice, etc. the wait may be just that, a wait.
Brian

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Old 02-02-2005, 06:05 AM
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When I talk about "dye-back" I'm not talking about the shrinkage that the normal person would even notice. I'm talking about that very small shrinkage that doesn't show up until the following summer, after sitting out in the blistiring sun all season.
Every "show car" owner I've talked too that's had his car for more than a couple of years has admitted he's had to go back and color sand and rebuff. It's that little texture in the paint that you can't see unless you get down and sight across the panel with a good eye when it's very clean and waxed. I know this is real "knit pickin" but I am a believer that all paint will eventually do this to some degree. To say a car has had absolutely no dye back after years of use, I'd say to the normal eye maybe, but all paint will shrink a little bit more down the road.
Waiting a little longer between priming/painting and waiting longer before color sanding/buffing really does minimise this.
But then I am to much of a perfectionist and I never have hit "perfect" yet. But I am getting closer.
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Old 02-02-2005, 02:59 PM
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I totally agree, paint doesn't completely cure for at least 90 days according to every paint rep I've ever talked to. The difference on dry time with the primer could make an additional 30, 60, ?? days if solvents are trapped below the paint. The jobs that are allowed to cure between undercoat applications always show less shrinkage and dieback. Just makes sense IMO
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Old 02-03-2005, 12:09 AM
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Bob, you can drop the "every paint rep" because I am telling you with proper temp most any 2K product most certainly does cure way before 90 days. Listen, I am not saying it doesn't hurt to wait. Please, read this next line slowly, "trapped solvents DO add to the need for the wait", IF everything is perfect, anything over a few days is overkill.

"Something" is being pushed if you have and noticable shrinkage or die back, period.

Guys, I don't know you personally, I have never spent the afternoon with you looking at cars in a show, or spraying paint. I have no idea Clark if you are "normal" or some super human with xray vision. I have no idea it you guys do every thing perfect and have such a keen eye that you see a microscopic shrinkage that us "normal" people don't see. There is nothing personal here, understand that. I am not saying you dress funny or you kids are homely. All I am doing is stating FACTS about paint and it's application. You can be mad at me for questioning your integrety but you would be wrong. You can be mad at me, but just take what I say and put it in your memory banks for the next project. It sure isn't going to hurt to just think about it, is it?


There are a number of factors that will lead to "shrinkage". What degree of shrinkage? Anywhere from total dieback the next day to a microscopic premature loss of gloss or smoothness on the surface months later. As you mentioned Bob, under cured product is one. If for some reason the paint primer or clear isn't properly mixed, the hardener was old, the temp was too low at application, etc. The other is too much solvent remaining in the film. Too heavy of coats, too many coats, too little flash time, too "slow" a reducer for temp, over reducing, etc.

Every one of these factors has a WIDE open door, HUGE, WIDE open door. One mans "med wet coat" is another mans "bomber coat". Even if you followed every one to the letter, but was on the "outer limits" on all of them (I call that when the "Planets are aligned") you can have shrinkage or other "failures". You are talking about exaggerating just ONE of these manufactures recommenations, the "window" before top coating. How about you "exaggerate" others? You may not know it, but you could be pushing something, exaggerate the flash time between coats to the MAX recommended in the tech sheets. Exaggerate the "wettness" of the coat, I don't like to say this because you really can spray it too dry, so don't do that, but apply it a little faster than usual. I like to say, apply your primer like it was a synthetic enamel top coat you wanted to be real nice. You aren't going to bomb that on, or you will have it on the floor. Really watch the temp and the solvent choice. Bring all these factors a down from the "outer limits" of the tech sheet recommendations.

It will all reduce shrinkage.

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Old 02-03-2005, 12:46 PM
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I agree with that, a lot of things reduce shrinkage.
But it doesn't eliminate it. I've seen cars with glass smooth
finishes for over two years then shrink just a little more.
Any good painter would notice it, wether it's an issue is
of personal taste. Most of the really perticular "show car" people
opt to buff it out again. Most people like my wife would never notice it,
it's still better than most new cars.
I'm sure with all my conditions not being perfect I do push
the limits, as with most painters. That's why I recommend to anyone to
wait longer between painting and buffing.
Most painters are not in ideal conditions.
I'm not saying you have to do it, I'm saying it'll help a lot,
especially for someone new. It could save a paint job.
Isn't that what this forum is for? Afterall, you "pro's" probably
don't need it like the rest of us. I think this forum is starting to
self destruct, too many of us are now replying to each other through
the private email just to avoid the "pro's" on the thread.
Isn't that ironic?, the very source of info we're looking for is what some are now
trying to avoid. You "pro's" would be amazed of how
much is going on without you. What a loss.
So in the future, everyone, think about how your response really
sounds to a newcomer. There has been a lot of people turn away
from this forum because off it. I know it's not intentional but IS happening.
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Old 02-03-2005, 02:01 PM
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the private email just to avoid the "pro's" on the thread.
Isn't that ironic?, the very source of info we're looking for is what some are now
trying to avoid. You "pro's" would be amazed of how
much is going on without you. What a loss.
So in the future, everyone, think about how your response really
sounds to a newcomer. There has been a lot of people turn away
from this forum because off it. I know it's not intentional but IS happening. [/B][/QUOTE]
*******************************************

Oh this forum will be here long after you, I or anyone else is gone.

To avoid the pro's is an interesting concept and thats fine but why be on here if thats the case? You stated recently that you knew the lacquer primer was not the same by smell.
I pointed out you cannot smell lacquer resin, so if that upset you than you should have said that to a friend or paint jobber who would agree with you and not hurt your feelings.

The best part about this place is if you take a look you have a lot of experts on here who all have their "specialty" and it keeps bad advice from filtering through because everyone of us have been corrected before and its a great check and balance.
If you don't want the truth, there are a lot of sites out there like A-Z that high school kids write in and you can be king of the hill!

Words have no personallity so don't get your pannies in a wad.
My dad always said if your talking, your not learning a thing.
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Old 02-03-2005, 04:38 PM
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Quote:
Bob, you can drop the "every paint rep" because I am telling you with proper temp most any 2K product most certainly does cure way before 90 days. Listen, I am not saying it doesn't hurt to wait. Please, read this next line slowly, "trapped solvents DO add to the need for the wait", IF everything is perfect, anything over a few days is overkill.
Brian, I've noticed some degree of gloss reduction on everything I've ever painted after it sets awhile-haven't you? If you polish your jobs again after 30, 60, 90 days doesn't it look better to some degree? This is very evident on the jobs that were perfected with sanding and buffing to a degree that can't be improved on- they always died back some degree after a period of time, look closer man. I just like to let my primer set awhile before sanding, it does dry harder, so to me that means it is curing more. After ninety days you can be sure all the paint drying is done, polish it again the gloss will improve and it will stay like that. JMO- No offense, I respect your opinions, but on a high dollar job I will continue to let the primer set ahile.

Last edited by baddbob; 02-03-2005 at 04:45 PM.
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