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  #1 (permalink)  
Old 12-17-2004, 12:56 PM
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Flash time

I posted this accidently in the wrong place at first, so
I'm placing it here hoping to get more response.
(I'm a little new at this)

My "DuPont" base paint says to clear coat within
24 hours. I understand from reading this forum that
giving a little extra time for the solvents to dry before
topcoating gives better results, makes sense to me.
My question is will waiting the full 24 hrs (by waiting
the next day to topcoat) have any drawbacks like
risking good adhesion? And will painting in cool weather
broaden my window for recoating?
There's usually not enough time when I get home from
work to base and clear in the same evening.
Waiting untill the next day to clearcoat would be nice.
Thanks.

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Old 12-17-2004, 01:15 PM
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BC and CC bond together to make one.....

As soon as you can touch the bc with your finger and it feels dry,
( be sure an do this checking on the masked area next to the paint) that means it has flashed and it is ready to shoot the cc.
The sooner you do, the better the cc will adhere to the bc. If you wait to long you will have to scuff the bc and re shoot it.

Troy
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Old 12-17-2004, 01:25 PM
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Thanks Troy. That's the way I've always done it.
I was just starting to question if I was not waiting long enough.
After reading so much on this site about solvents being
trapped and that many problems are from not waiting long
enough it had me wondering. The mfg says wait 30 min.
for base to dry, sometimes I thimk I need a little longer
but I get impatient.
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Old 12-17-2004, 01:31 PM
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30 min. is a long way from 24 hr. which in my opinion is to long.
30 min. sounds about right.

Troy
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Old 12-17-2004, 01:40 PM
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Martin Senor

MS actually recommends wet on wet for clear over base,it cross links better ,no problems with solvents. I`ve done it and it works good.
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Old 12-17-2004, 03:12 PM
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Jerry: I'm really surprised you can get away with that.
I put my clear on to soon once and the metalic started to mottle.
I had big splotches all over . I let it dry a couple of hours,
then dusted on enough base to cover it and recleared.
It still looks good now almost 3 yrs later (my car).
I don't think I'll ever rush it again. And what's all this talk on
the other threads about these long dry times before clearing?
Now I'm hearing just the opposite.
I've been painting for over 25 yrs and I still learn new
stuff everyday. Some may argue if it works for you why change
but I'm always looking for ways to improve and don't ever
want to get that narrow minded. Any info from the rest
of you guys is greatly appreciated. I just want to hear more
different ways.
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Old 12-17-2004, 03:22 PM
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Wet onWet

I think Martin Senor is the only one that recommends that procedure. Check your product and follow their instructions. I would hate to see you ruin a paint job because of me. Jerry
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Old 12-17-2004, 06:05 PM
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Unless something has just recently been changed Martin Senour does NOT have a recommendation to apply the clear "wet on wet" to the base. They do however have a "limited flash" recommendation to apply the two coats of clear wet on wet. But those two coats of clear are to be applied over a flashed base. 10 to 40 min depending on base coat reducer "speed" used. With a top end of 7 days is the flash time before top coating with clear for the base.

Last edited by MARTINSR; 12-17-2004 at 10:40 PM.
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Old 12-17-2004, 07:47 PM
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As far as what we were talking about on the other treads simply put, always go to the outer end of the recommended flash time.

Trapped solvents are the number one cause for failure, period.

Proper atomization, gun setup, CFM supply, solvent "temp" or "speed" choice, gun speed, overlap.......these all can change the amount of solvent that could get trapped as well.

If you were to only make one mistake along the way, poorly atomized gun, or too slow a reducer for the shop temp,you will likely get away with it. But if you start adding them up, you are in for trouble.
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Old 12-17-2004, 10:57 PM
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I used Martin Senour for 20 years, I never heard or read where you applied clear on a wet base.

The only problem I ever had was when painting graphics, and the base would dry to much and the clear would not adhere right.

Troy
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Old 12-18-2004, 05:13 AM
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Quote:
Originally posted by troy-curt
BC and CC bond together to make one.....

As soon as you can touch the BC with your finger and it feels dry,
( be sure an do this checking on the masked area next to the paint) that means it has flashed and it is ready to shoot the cc.
The sooner you do, the better the cc will adhere to the bc. If you wait to long you will have to scuff the bc and re shoot it.

Troy
*******************************************
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

A couple things here need to be understood so no one messes anything up.

1) clear and base do not become one, we are not cooking molecules here.

2) the clear does not melt the base to stick, a slight softening only as anything more would re-flow the metallics and we would have uneven metallics all over the place.

3)The sooner you clear the base the better adhesion.
This is wrong as a graft can be drawn as to when best adhesion is.
The adhesion is weakest at first as there are more solvents left in base than get stronger and are STRONGEST from about midway of the manufacturers recommended window time.
So if window of clearing is 22 hours then perfection will be 10-12 hours.

4) a foot note to a comment made:
If the manufacturer says can be cleared with in 24 hours there is always plenty of safety build in because of temperature and humidity factors- so if it says coat within 24 hours and you paint in 22 hours you have not hurt yourself a bit.
You must remember tech sheets are written based on 70-75 degrees and the manufacturer must allow for extremes if used in Canada or extremes if used in Cuba.
A safety net is always built in.

Last edited by BarryK; 12-18-2004 at 06:31 AM.
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Old 12-18-2004, 08:27 AM
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MISS INFORMATION>

Quote:
Originally posted by BarryK
*******************************************
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

A couple things here need to be understood so no one messes anything up.

1) clear and base do not become one, we are not cooking molecules here.

2) the clear does not melt the base to stick, a slight softening only as anything more would re-flow the metallics and we would have uneven metallics all over the place.
-------------------------------------------------------------------------------
TC
This has already been established in the previous posts. Nothing has been said about cc melting the bc.

If all the different coats of a paint job didn't become one, you would not have adhesion.
-------------------------------------------------------------------------------


3)The sooner you clear the base the better adhesion.
This is wrong as a graft can be drawn as to when best adhesion is.
The adhesion is weakest at first as there are more solvents left in base than get stronger and are STRONGEST from about midway of the manufacturers recommended window time.
So if window of clearing is 22 hours then perfection will be 10-12 hours.
-------------------------------------------------------------------------------
TC
Really Barry,
How many shops can tie up there paint booth for 20-24 hours?

Tech. sheets says to apply the next coat or step when the previous one flashes.
-------------------------------------------------------------------------------

4) a foot note to a comment made:
If the manufacturer says can be cleared with in 24 hours there is always plenty of safety build in because of temperature and humidity factors- so if it says coat within 24 hours and you paint in 22 hours you have not hurt yourself a bit.
You must remember tech sheets are written based on 70-75 degrees and the manufacturer must allow for extremes if used in Canada or extremes if used in Cuba.
A safety net is always built in.
------------------------------------------------------------------------------
TC
I have painted thousands of cars, and never had one with solvent pop problems.
------------------------------------------------------------------------------

Troy

Last edited by troy-curt; 12-18-2004 at 08:38 AM.
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Old 12-18-2004, 09:19 AM
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TC
Really Barry,
How many shops can tie up there paint booth for 20-24 hours?
**********************************************
Learn to read! Once solvents are flashed you can paint as production shops and dealerships do, not a problem but for the beginner extra time is to their benefit as one they are not painting in a booth so conditions of air flow and hear are not the same.
We also have to go with understanding a professional painter has proper tip and gun adjustment and this may not be the case with a newbie doing it at home.
So the better the job, witch do it your selves have more time than money, letting it set is to their benefit.Bk
**********************************************

Tech. sheets says to apply the next coat or step when the previous one flashes.
*********************************************
That is right, tech sheets are written for the Chevy dealer, high production and perfect conditions.Bk
*******************************************

If all the different coats of a paint job didn't become one, you would not have adhesion.
**********************************************
Duh!
So how can clear peel from base if one and leave the base?
How does base stick to primer as it is not one?
How does primer stick to epoxy, as it is nor one?
bwk

I bow to you as I know of no painter that has done a 1000 jobs and never had a solvent pop (if your using base/clear)
I sure can't say that. Lacquer-OK. bwk
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Old 12-18-2004, 10:13 AM
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BK
Duh!
So how can clear peel from base if one and leave the base?
How does base stick to primer as it is not one?
How does primer stick to epoxy, as it is nor one?
bwk
-----------------------------------------------------------------------
TC
It's called adhesion
The whole paint job becomes one, if it is done right. As you know more about painting than any one else, you should know this.

Clear peels because it didn't have the proper adhesion. usually because the flash time was to long.
------------------------------------------------------------------------
TC
The org. post didn't ask about painting conditions and equipment.
The question was, how much flash time.
-------------------------------------------------------------------------
BK
*********************************************
That is right, tech sheets are written for the Chevy dealer, high production and perfect conditions.Bk
*******************************************

TC
And that's what we all strive for. The perfect conditions.
Lets stay with the facts, and less derogatory remarks and personal attacks. There is more than "ONE" good painter on this board.

Troy
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Old 12-18-2004, 10:43 AM
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Come on now guys, let's not have a peeing match. This is very , very good stuff, let's not cloud it up.

When I say that trapped solvent is the number one cause of failure I am not kidding. Trapped solvent in one way or another does more damage than any other mistake, PERIOD.

Because of this, it is very important to talk about.

Troy, I think the most important word is "optimum". It is optimum to wait out that flash recommendation. Not that everyone does it, certainly not in collision shops. There are lots of things that go on in collision shops that is far from optimum.

The one thing a shop has in it's favor that a home hobbyest does not have is the booth. You can push a lot more when you have booth with the air movement it provides to "pull" the solvents out of the film.

With a car sitting in a garage with a little box fan in the window to suck out the overspray, you have a completely different condition. These flash times, solvent temp choice, gun speed, gun setup, air supply (read that CFM) etc. become much more of an issue.

Honestly Troy, clear coat peels are caused by applying the clear too soon far more than waiting too long. I saw plenty of clearcoat peels from collision shops, the S-W recoat max is seven days, the collision shop certainly didn't wait too long that is for sure. They pushed it, to get the cars out the door and trapped solvents under the clear. The next time you see a "peeler", try this. Peel some of the clear off and stick your nose down to the base that has been exposed, you will many time smell solvents! You will smell the solvents that were trapped under the clear!


Barry, on that note, I always wondered about that seven day window thing, how in the heck can they have it that long when similar products are so much less at 24 hours? I can not imagine waiting 7 days to clear something, I have waited till the next day a number of times, but there is no way I would wait 7 days, that just gives me the willys thinking about it.

Last edited by MARTINSR; 12-18-2004 at 10:55 AM.
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