I think I figured out my paint issue - Vintage Mustang Forums
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post #1 of 10 (permalink) Old 06-17-2019, 08:40 AM Thread Starter
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I think I figured out my paint issue

I remembered later on that I had used some rust removing etch product on a part of the underside of the trunk lid. It mists out of the spray bottle and some of it misted all over the rest of the deck lid which was e-coat and I didn't remove all that e-coat. I couldn't see the little dots that stuff caused but once I primed and tried to paint it my guess is that they decided to show up in the urethane. That is the only thing I can think of that could have done that. What I am doing now if I need to put this on the car is I spray it onto a blue paper shop towel until it is wet and then put the wet towel on the area I want to treat. I could also soak it into a cloth and wipe it on but stupid me, I was just spraying it onto the metal.



At any rate, I have taken it back down to bare metal, sanded it 3 times, wiped it down 5 times including air blowing it off and tacking it multiple times. I have it back in 2 coats of epoxy now. I'm having stress over the thought of shooting the urethane on it again so I fixed the runs in my rear quarter panels and put about 30 glazing puddy touch up's on my rear fiber glass bumper to get it completely smooth. I shot it with 2 coats of urethane primer "surfacer" which didn't really surface it even after I sanded most of it off. The imperfections and pin holes were still there. I also now have that in 2 coats of epoxy waiting on a good weather paint day.



Its been raining again where I am and is supposed to rain again today which means around 100 percent humidity. What is weird is I watched a video of a couple of garage / shop painters in Florida spraying House of Kolor candy orange onto a hellcat engined Miata and they also clear coated it and it was raining most of the time through that. All they had was some exhaust fans to blow the solvent fumes out. Seems like I should be able to spray my stuff in this weather but I'm afraid to try.



I think that I will just use a good body filler where required and touch up the other small imperfections and not spray any polyester high build primer at all on this car. I am managing to fix everything without it. The other filler I am using is the fiberglass short strand for areas I have welded(it is supposedly water proof and works as a DTM filler).
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65 2+2, 331, C4 presently apart for complete a restore
1979 Ford F150 custom, 302, C4, AC, tilt wheel, main transportation

Last edited by macstang; 06-17-2019 at 08:47 AM.
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post #2 of 10 (permalink) Old 06-17-2019, 10:04 AM
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I remembered later on that I had used some rust removing etch product on a part of the underside of the trunk lid. It mists out of the spray bottle and some of it misted all over the rest of the deck lid which was e-coat and I didn't remove all that e-coat. I couldn't see the little dots that stuff caused but once I primed and tried to paint it my guess is that they decided to show up in the urethane. That is the only thing I can think of that could have done that. What I am doing now if I need to put this on the car is I spray it onto a blue paper shop towel until it is wet and then put the wet towel on the area I want to treat. I could also soak it into a cloth and wipe it on but stupid me, I was just spraying it onto the metal.



At any rate, I have taken it back down to bare metal, sanded it 3 times, wiped it down 5 times including air blowing it off and tacking it multiple times. I have it back in 2 coats of epoxy now. I'm having stress over the thought of shooting the urethane on it again so I fixed the runs in my rear quarter panels and put about 30 glazing puddy touch up's on my rear fiber glass bumper to get it completely smooth. I shot it with 2 coats of urethane primer "surfacer" which didn't really surface it even after I sanded most of it off. The imperfections and pin holes were still there. I also now have that in 2 coats of epoxy waiting on a good weather paint day.



Its been raining again where I am and is supposed to rain again today which means around 100 percent humidity. What is weird is I watched a video of a couple of garage / shop painters in Florida spraying House of Kolor candy orange onto a hellcat engined Miata and they also clear coated it and it was raining most of the time through that. All they had was some exhaust fans to blow the solvent fumes out. Seems like I should be able to spray my stuff in this weather but I'm afraid to try.



I think that I will just use a good body filler where required and touch up the other small imperfections and not spray any polyester high build primer at all on this car. I am managing to fix everything without it. The other filler I am using is the fiberglass short strand for areas I have welded(it is supposedly water proof and works as a DTM filler).
What filters have you been using? How do you like the short strand DTM stuff?

Flade
68 289 convertible Candy-apple red & white
66 200 coupe Blue
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98 GT convertible White & black
98 V6 convertible White & tan


Last edited by Flade; 06-17-2019 at 10:12 AM.
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post #3 of 10 (permalink) Old 06-17-2019, 01:11 PM Thread Starter
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I have a water trap/drain on the line at the compressor hook up and an inline oil/air filter at the gun. The inline filter is new. The urethane I shot on my rear quarter extensions had no dots or bubbles at all like the decklid so this dot or bubble issue is unique to the decklid. I even sprayed the quarters with left over mix I had just hit my deck lid with.

The fiberglass filler is great for coverage over butt welded metal or welded seams that you grind down smooth and metal patch repairs. This is what the instructions said it is really made for but you can also repair fiberglass with it which I haven't tried yet. I will probably use it to restore my VW fiberglass body because it needs some attention.



It appears to be really strong, doesn't shrink and sets hard as a rock. Hard as a rock means if you let it set up completely it is going to be difficult to sand. It pays to start knocking it down while it is still a little pliable. It also has a pretty short working time like 4 minutes or so. I've been using 3M's particular brand but it looks and works just like every other version of marglas from what I can tell. Evercoat sells something that looks like it and USC does and most everybody that makes filler sells a version of this. I don't know if they are all equal though.


65 2+2, 331, C4 presently apart for complete a restore
1979 Ford F150 custom, 302, C4, AC, tilt wheel, main transportation
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post #4 of 10 (permalink) Old 06-17-2019, 07:42 PM
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Originally Posted by macstang View Post
I remembered later on that I had used some rust removing etch product on a part of the underside of the trunk lid. It mists out of the spray bottle and some of it misted all over the rest of the deck lid which was e-coat and I didn't remove all that e-coat. I couldn't see the little dots that stuff caused but once I primed and tried to paint it my guess is that they decided to show up in the urethane. That is the only thing I can think of that could have done that. What I am doing now if I need to put this on the car is I spray it onto a blue paper shop towel until it is wet and then put the wet towel on the area I want to treat. I could also soak it into a cloth and wipe it on but stupid me, I was just spraying it onto the metal.
I would agree with your findings, rust etch products can make a mess of a paint job if not thoroughly naturalized or removed. Im my experience, paint manufacturers frown on using these products because of the exact problems you're having. Too many people use them and don't get the surface neutralized, then when they have paint issues they blame the paint or primer.

I wouldn't fret over priming or painting when it's raining outside as long as you've got air moving and it's not real humid in the shop. If body shops stopped what they were doing when it rained, there are parts of the country where a car would never get completed.

65 coupe 5.0L/5 speed
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Last edited by Lightning; 06-17-2019 at 07:46 PM.
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post #5 of 10 (permalink) Old 06-17-2019, 11:33 PM Thread Starter
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Well, can I get my I-am-a-BIG-dummy award or trophy now? Good grief, LOL.


I re-sprayed my rear quarter extensions today. They came out beautiful. It is a bit weird standing there watching this stuff go through its transformation from wet to dry. So I was about out of urethane in the paint pot so I mixed up enough more to spray my fiber glass bumper which was also smoothed out, primed and ready to spray. Well for whatever reason I don't even know, I added in a small amount of slow reducer to the mix. Couldn't hurt anything right?



Well, adding reducer was a really BAD IDEA and I didn't put a lot in but it appears it was still too much. The reducer thinned the mix too much and I now have a run 2 feet long across one side of the bumper. The rest of the bumper is like black glass, absolutely beautiful, but I will be sanding it again over the next day or 2 for another do over. I think I am now understanding that with the temp in the mid 80's, the standard 3 to 1 mix for the paint was thin enough already. The reducer made it too thin regardless of the fact I was spraying the slow stuff.


So tonight I fished around online and found a website, 7 common paint mistakes. #1 cause of runs, sags and curtains? Improper reducer or too much reducer. I can't be totally sure because the others listed are excessive thickness of the film, insufficient flash time, inadequate air pressure, poor technique. I qualify for at least 2 of those also probably.


Considering the price of this material, I have wasted a fair amount of money and still learning everything the hardest way possible.


65 2+2, 331, C4 presently apart for complete a restore
1979 Ford F150 custom, 302, C4, AC, tilt wheel, main transportation

Last edited by macstang; 06-17-2019 at 11:36 PM.
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post #6 of 10 (permalink) Old 06-17-2019, 11:46 PM
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Originally Posted by macstang View Post
Well, can I get my I-am-a-BIG-dummy award or trophy now? Good grief, LOL.

still learning everything the hardest way possible.

This is how it sticks in your brain for the next restoration. We all have a lot of lessons by the mistakes we make. I know I sure have my fair share.

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post #7 of 10 (permalink) Old 06-18-2019, 01:12 AM
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Definitely was the quantity of the reducer and not the speed or it, although we're all guilty of excessive film thickness at some point of doing this work too. I always use medium reducer and in hot weather I find Im better off using a shot of retarder instead of a slower reducer or more reducer, it only takes a little retarder to make a big difference and you don't run the risk of runs from over thinning. Even when its not hot, I always add a touch of retarder to my last coat of clear, it helps it flow out and achieve that flat as glass look.
If you don't use the manufacturers tech sheets for the product you're spraying, you should get in the habit, it can keep you out of trouble. For me, regardless of how many times I've used a product, I look over the tech info to refresh my mind. In the primer phase an issue like you had is no biggie, but mess up $1000 worth of finish and it'll ruin your day.

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Last edited by Lightning; 06-18-2019 at 01:15 AM.
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post #8 of 10 (permalink) Old 06-19-2019, 08:21 AM Thread Starter
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I thought it might help somebody else to tie this one off and post the results of my last go around of try and see changes.


I went over to talk with somebody I know who runs his own shop, has built a few drag cars and knows a lot more than I do. He also knows the paint stuff pretty well so we brain stormed for a while. I needed a plan B because nothing else I had tried was working.



First, I was trying to spray this stuff out in the sun and here in Texas if the ambient temp is say 85 or 87, the part being sprayed might be reading 110. This is notta good. I noticed it sort of abruptly when I reached down the other day to pick up my pocket knife which had been laying on the concrete in the sun. It was so hot I couldn't hold it so that had to be not a good thing when the paint hit a surface that hot.



The second thing I discovered and can I get that I-am-a-big-DUMMY trophy passed around again is that I had the paint flow cranked too far open. There are so many potential variables involved in wringing anything like this out, particularly if you are new at it(like me, never sprayed single stage before except out of a spray can), it was hard to find this problem. I had left it set on what sprayed the epoxy the best which is a lot wider open. I trimmed the gun back to 2 turns out and sprayed my rear quarter caps in the shade. They came out great.



It now occurs to me that the paint vendors need to include the flow rate setting somehow in their specs on air pressure and fluid tip size for dummies like me.



I feel better now, LOL.


65 2+2, 331, C4 presently apart for complete a restore
1979 Ford F150 custom, 302, C4, AC, tilt wheel, main transportation
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post #9 of 10 (permalink) Old 06-19-2019, 01:59 PM
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It now occurs to me that the paint vendors need to include the flow rate setting somehow in their specs on air pressure and fluid tip size for dummies like me.
Any quality coating will have a tech sheet available that lists among other things tip size and pressure at the cap. Other info includes mix ratios, substrate prep, compatible undercoat material and recoat/top coat windows.

Here's one for TCP Global single stage acrylic urethane. You can get the sheets either from your jobber or better yet online from the manufacturer. http://images.tcpglobal.com/sds-sheets/techsheet_au.pdf

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post #10 of 10 (permalink) Old 06-19-2019, 02:48 PM
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Considering the price of this material, I have wasted a fair amount of money and still learning everything the hardest way possible.
I can share similar stories about rebuilding the 351C for the Pantera - simple mistake that cost me THOUSANDS of dollars and a 2nd rebuild within the first 900 miles! Thought I was going to save some money doing it myself, but an education is not free!

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