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Old 01-28-2006, 10:42 PM
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Hey Barry, Hey Martin 15 degree rule

You always see someone asking a question or making a comment about temperture and how it affects painting. One guy did a "test" with the quality of mud over epoxy. He had mentioned that he heated the epoxy to speed up its dry time. Since that thread I've been thinking,at a recertification a couple of years ago I remember them talking about the "15 degree rule". For every 15 degrees over 70( because 70 is the temp that all p-sheets are set up on as far as PPG goes) you cut the flash time or dry time in half. For instance,if a products flashes off in 15 minutes@70 degrees then it will in turn flash off in 7 minutes@85 degrees. Is this true for all paint lines? if the guy heated up the epoxy to speed up flash and then put mud on it that heats up as it dries I would say that the window ran out on the epoxy. Most people who use epoxy under mud my not realize how hot drying mud is and what it can do to flash time.
Now I'm not picking on that guy I just want to make sure that the "do it yourselfer" understands this rule. In the summer inside my paintbooth( I do collision painting) I have to almost go back to back coats from sealer to clear because of the heat and humidity and the "15 degree rule". I just want to be sure others know this. Going past a flash time can cause you great pain depending on what you use.

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Old 01-29-2006, 05:27 AM
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I think he is on the right track but this does vary by product to a degree.

I have always told the painters with my product every + or - 10 degrees
you can figure a change of flash or any other statement in the tech sheet by adding to subtracting 15%.

I think a 10/10 or a 15/15 rule is a fair Gage to go buy because like you say most people if painting at 90 degrees are doing everything written in the tech sheet for 70-75 degrees. Anyway it is in the ball park.

A few years ago we did a sampling on the clears (I have 6) with a temp range of 40 to 110. (35% humidity) Humidity also is a very big factor.

This is on my product and did not test anyone Else's and all products are made different and the core resin is probably the biggest factor as to the reaction. (note of the six clears there are three different core resins used)

The rise of 10 degrees from 65 degrees varied from 11-17% in change up to
105 degrees than changed real fast with much larger jumps.

The reason for the large percentage gap in my product was the fast activators and the spot type clears were showing higher percentages but they are made to cure faster.

At the 100 degree mark everything got off kilter as the core resins I use are low bake resins so that changes everything.
A low bake resin you would bake at say 110-125 degrees for 10-20 minutes where most you would bake at 130-150 30-60 minutes. (just for comparison)

Going from 70 degrees to 40 was very constant until we hit 50 degrees and than there was a big gap with the Turbo, Euro and the universal still staying in range and the other three "giving it up so to speak"

Either way 10/10, 15/15, 15/10, 10/15 are all going to be a fair guide for the home user to use and should be close for most clears and primers and they can't go wrong using any of the Percentages as a guide so they can make general adjustments.

Re: Mud and epoxy all I can say on that one is it would have little or no effect on mine.

This is something everyone needs to know and I don't think it was ever brought up before. Great question.
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Old 01-29-2006, 06:32 AM
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To try to clarify this, If you have the reducer for that temperature range, you still adjust the times, according to the temp difference from 70 deg? If the recommended flash time is 15 minutes, and it is 85 deg, you've got to spray the next coat at 7 minutes, and not wait the 15 minutes? Doesn't it work to your advantage to wait that extra time to avoid solvant pop?

Aaron
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Old 01-29-2006, 07:09 AM
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Aaron,

The test was done with the proper grade reducer at each temp range.
You are right longer flash is better as most tech sheets are written for production type work.

Also on the math, it would be done this way, not clumped.

70 deg = 5 minute flash time.
60 deg = 5 divided by .85 =5.88 flash.
50 deg = 5.88 divided by .85 = 6.92

70=5
80=5 x.85=4.25
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Old 01-29-2006, 07:19 AM
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Also on the math, it would be done this way, not clumped.

70 deg = 5 minute flash time.
60 deg = 5 divided by .85 =5.88 flash.
50 deg = 5.88 divided by .85 = 6.92

70=5
80=5 x.85=4.25

WHEW! I need a new watch! LOL

Aaron
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Old 01-29-2006, 12:41 PM
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I have never really heard of this "rule" because with my training you were discuraged from pushing it. So, in other words there may have been something mentioned refering to this "rule" where you "could" cut the flash time in the higher temp, but there is really no reason TO cut it.

The epoxy/filler test we are discussing had something go wrong, don't know what, but something. Your example would mean that the fillers heat help "kick" the epoxies cure up a notch which could have an effect on adhesion in my opinion. So you may be on to something. I do think it was that and other issues where the "planets where aligned" to create the failure.

If we look at the test for what it is, it is still valuable. If you follow the test, and apply epoxy under the same conditions you are not getting the improved adhesion qualities of the epoxy. If you have to apply the epoxy in that way, you are better off applying the filler over the bare metal and not using the epoxy. It looks like he proved the very reason why 95% of body shops in America apply the filler over the bare metal, they don't have the time to apply the epoxy primer properly.

THAT it did prove, so it is a valuable test.

Brian
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Old 01-29-2006, 07:33 PM
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Quote:
Originally Posted by MARTINSR
I have never really heard of this "rule" because with my training you were discuraged from pushing it. So, in other words there may have been something mentioned refering to this "rule" where you "could" cut the flash time in the higher temp, but there is really no reason TO cut it.

The epoxy/filler test we are discussing had something go wrong, don't know what, but something. Your example would mean that the fillers heat help "kick" the epoxies cure up a notch which could have an effect on adhesion in my opinion. So you may be on to something. I do think it was that and other issues where the "planets where aligned" to create the failure.

If we look at the test for what it is, it is still valuable. If you follow the test, and apply epoxy under the same conditions you are not getting the improved adhesion qualities of the epoxy. If you have to apply the epoxy in that way, you are better off applying the filler over the bare metal and not using the epoxy. It looks like he proved the very reason why 95% of body shops in America apply the filler over the bare metal, they don't have the time to apply the epoxy primer properly.

THAT it did prove, so it is a valuable test.

Brian

It wasn't meant to be used to cut flash time it is meant as a warning. My training is the same as yours,not to push any part of it but without the knowledge of such "rule" you will be pushing the limits of a window of opportunity to apply the next coat or product. The reason why I have "rule" in quotation marks is that I can't find it in print(from PPG) but I do know it exists. Just want the masses to understand that waiting TO long can be as dangerous as not.
Brian, I hope I understood your first paragraph and replied accordingly. Sometimes I don't quite follow what someone is saying and reply in the wrong way.
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Old 01-29-2006, 07:43 PM
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I think we are on the same page AC, my thing is, 15% one way or the other isn't going to make a big deal. Your typical flash time is a wide open window much further than most use. So if the recommended flash is 20 min mininum and it is much hotter so the guy "should" cut the flash a little, waiting the full 20 isn't going to do a thing being the real window for recoat is much more, hours in most cases. That is my point.

The danger of speeding up the flash times is much more real than slowing them down. I have see VERY few failures do to waiting too long between coats, clears, yes,but not basecoat.

Brian
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Old 01-29-2006, 08:01 PM
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Cool,but my bet is you have seen some damage from too long flash of base,delaminaton. Not ALL delam's are caused by this but a precious few are. Also,this is one of those things that should be on a persons mind and not something to live by. Too fast is the leading cause of problems,I agree but as I was taught, 1 time in 100 it could go wrong and I want to help that "1 time" person with any info I can give. Epoxies 7day window is mentioned but never basecoats or even clears.
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Old 01-29-2006, 08:33 PM
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Quote:
Originally Posted by MARTINSR

The danger of speeding up the flash times is much more real than slowing them down. I have see VERY few failures do to waiting too long between coats, clears, yes,but not basecoat.

Brian
I agree. Piling on the products fast usually leads to piss poor performance.

AC/DC, I shot some primer surfacer today, applied three coats waiting 20 minutes between the first two and 30 minutes before applying the third. These panels that were primed will set for three or four weeks before they are final sanded. Could I have shot three coats on back to back with no flash time and not have any problems considering the 3-4week cure time before sanding? Probably. But with this job there's no sense in risking shrinkage so the 50 minutes of flash time is no big deal.

Collision work is a whole different story, products get pushed to the extreme. Example-Years ago I shot a complete with Chroma Premier in twenty minutes! I set the booth at 95 degrees, one coat of sealer, two coats of black base, and two coats of clear! Wet on wet, hit the bake, washed my guns, wiped the sweat off, and crossed my fingers- now that's product abuse! Not the right thing to do qualitywise for sure but surprisingly the job looked just fine when it came out of the booth and got delivered. Bob
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Old 01-29-2006, 08:53 PM
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Being that car was black that you painted, I will bet it has failed by now. Black will retain much more solvent and it surely delamed. Bob, lol, that brought back a memory. Sad thing is, the building where this happen is gone and MORE friggen apartments are being built! This area is going down the tubes.

Anyway, it was a 69 Mustang and on delivery day, just an hour or so from when the guy was to pick it up I was unmasking a little spot job on the fender and the darn paint (from a previous job) peeled up off the primer. This car had been painted or spoted DOSENS of times, the paint was a foot thick. Anyway, it was out side parked in the sun on a very hot day. I sanded the spot, primed it (lacquer) sanded it, painted it, cleared it, blended it out (all lacquer), AND buffed it in about twenty minutes!!!! No kidding! The metal was hotter than hell and it was dry RIGHT NOW.

I had already told him I never wanted to work on it again unless he was going to have it stripped. So I never did, but did check many months later on that repair when I saw it parked, still looked good. Thank God he garaged it every day.

Brian
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Old 01-30-2006, 08:56 PM
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OK, I can see that I need to explain a little. Here is the sernario, a DIYer bases his car Saturday, evening rolls around and so do the gnats. He says to himself "I'll clear it tomorrow after the gnats leave", its summer time and humid as hell. With that in mind he could burn up his window. I've seen guys who have left bike parts sit for 2 weeks before finishing them and they DID NOT rescuff the part! Why did they leave them sit,you say? Had other projects in the mix.

Now badbob, did you mix new primer with each coat OR do you have enough to do the job in one mix? With my products I would have to make new primer per each coat because of a potlife issue with the time you waited.Just because it is still sprayable DOES NOT make it good to spray. Also I am the exception in collision painting. I have p-sheets and I follow them. That way when some butthole rep comes in to fix a problem I might have I can proudly say that I DO NOT HACK MY PAINT!!!!

And this post was meant to include ALL products not just base. I know for a fact that clears will be the first to fail if you wait to long BUT everything has a window and I wanted to share it with you guys. I believe that pushing products has been WELL documented on here and I totally agree but there are two sides to everything.

If I seem a little pissy I don't mean to.

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Old 01-30-2006, 09:25 PM
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AC/DC, yeah I mixed the primer at each coat that way there's no waste as I guage how much I need to cover on the first application. I posted the example of my stupid 20 minute paint job just to provide an example of what can really go on in the world of in and out collision work. Many techs have a heatlamp cooking during the prime and after to push the cure time to it's max. The average DIYer doesn't know the product's limits and can really screw things up if things aren't right so a good amount of cure time with good flash time is just insurance there won't be any shrinkage problems down the road. Just my opinion. No reason for anyone to take offense IMO, sorry if they do. Bob
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Old 01-30-2006, 10:08 PM
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Quote:
Originally Posted by AC/DC
If I seem a little pissy I don't mean to.
It's cool guy, we all get what you are saying, just discussing it. Clears are one that your point is VERY important. Letting a thin coat cure and then applying another coat over it can leave you with a total catastrophic failure.

Brian
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Old 01-31-2006, 07:43 PM
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We're all good! Just had to let them know that to fast is bad but there is also a limit the other way. When I said I had to go back to back from sealer to clear, I'm talking high air flow booth 100 plus degrees and high humidity. Most DIYers don't have the high air flow BUT the other two are possible.

Brian, I'm going to get in touch with my territory manager and have him dig up the info on "15 degree rule" so that I can share it with you if you are not familiar with it.
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