Polyester primer or not

R

robking

Promoted Users
Hey folks, as always thanks for your help.

I have one quarter panel that required a lot of metal work to bring back (apparently a tool box was left to slide around the trunk for years). I have pretty much skimmed the whole thing with Rage Ultra, and it feels good to a gloved hand. I sprayed it with like90 panel check and see some waviness however.

I'm getting ready to cover this with another round of black SPI epoxy and lightly block again with my new blocks from Dean. Once that's done, in a perfect world I'd like to move on to high build unless I find some glaring imperfections. Chris has a great post here about how to approach doing your high build:

High Build urethane primer vs. Polyester primer

I know that SPI dose not make polyester primer. However, I would like to hear both side of the argument. I have been online looking at the pros and cons of high build urethane and polyester primers. I have used polyester primer ( Clausen's sandy primer) in the past and I like the way it fills...
www.spiuserforum.com

On that same thread though Crash makes good points about using polyester over a particularly rough panel.

I'd rather not invest another $200+ in materials (sounds like Evercoat super build 4:1 is the way to go) if this is safely taken care of with high build urethane that I have to buy anyway. But I also can envision going multiple applications of high build and still fighting with it.

I've read a bunch of posts and still can't convince myself of the right way to go. I'd rather be painting than stressing. :)

Any advice on how to pick a direction is greatly appreciated.
 
Urethane 2k is intended for final filling of 180 grit scratches imo. Building with 2k urethane is a mistake imo because it shrinks. Polyester does not shrink like urethane high build. Some guys say polyester chips but I’ve not seen that when applied correctly. I use Clausen Sandy and Rust Defender poly primer.

Mandatory backyard hack disclaimer inserted here.

Don
 
dhutton01 said:
Urethane 2k is intended for final filling of 180 grit scratches imo. Building with 2k urethane is a mistake imo because it shrinks. Polyester does not shrink like urethane high build. Some guys say polyester chips but I’ve not seen that when applied correctly. I use Clausen Sandy and Rust Defender poly primer.

Mandatory backyard hack disclaimer inserted here.

Don
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Thanks Don, the area on this quarter that really needs attention is at least up high and less likely to get a rock. The lower part of the quarter is AMD patch panel and decently smooth.

I also saw mention of shrinkage (sorry cant help but laugh) with urethane on the other thread. Can that be avoided by giving it more time between application rounds?
 
robking said:
Thanks Don, the area on this quarter that really needs attention is at least up high and less likely to get a rock. The lower part of the quarter is AMD patch panel and decently smooth.

I also saw mention of shrinkage (sorry cant help but laugh) with urethane on the other thread. Can that be avoided by giving it more time between application rounds?
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I am guessing time in the sun would help but honestly I don’t try to build with urethane primer. I just use it to refine sand scratches. One of the pros can likely give you better advice.
 
Urethane properly applied doesn't shrink much. Where the bad rep comes from is when it's abused. I.E. pounding wet coat after wet coat on without proper flash time. Then sanding it shortly after and painting the same or next day. Trapping solvents. Applied correctly it's not an issue. Observe flash times, don't pound it on, give it a couple of days min before paint, shrinkage will be nill.

For restoration/ nice stuff I personally don't like either. SPI Epoxy builds well enough that it is an excellent choice for resto type stuff. Me personally I would use urethane before poly. I've never had luck with poly and not having chipping issues. One I did recently I used poly on the jambs and tops of the rockers and it chipped when I was installing the doors. My SnapOn plastic handled ratchet hit the edge of the rocker while tightening the hinges and chipped. Then I did it again on the other side even though I was being careful. Both places it was only the poly that chipped. Not excessive build and you could see some poly still clinging to the epoxy. Some poly seems to chop more than others. IDK YMMV.

I've gotten to the point these days where for most of what I'm doing, I'm only using SPI epoxy.
 
I have used Evercoat Feather Fill polyester primer on beat up panels like this '65 Buick:
LH Quarter Filler Work Needed 1.JPG


Both quarters were beaten up and the entire car had lots of little issues.

I view Polyester Primer as spray on body filler, so I didn't skim the entire panel first, just sprayed a fresh coat of epoxy primer and then shot three heavy coats of polyester primer, applied guide coat and block sanded with 180 grit.
LH Quarter - Poly Primer.JPG


From there I shot 2 coats of regular 2k build primer, guide coated and blocked with 320 grit, followed by 600 grit wet.
 
I see a lot of high end shops using polyester aka The Devil’s primer in six figure builds. More using it than not using it. Rust Defender is used extensively by Corvette restoration shops and was even used on the SPI cover car built by Ken Sungela….

Even my brother from another mother Charlie Hutton uses it… :p

Don
 
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I'm not arguing the advantages of it in the Shop Don. Builds nice, sands nice, etc. But just because high end shops use it doesn't mean it's what to use for longevity or to prevent chips or that it doesn't chip excessively. They use it because it's fast and it builds. If they were using what is best and what will be best for the car 20+ years in the future, every Shop would use epoxy only. Many of these guys probably don't even know about epoxy and what you can do with it.
I just think in the real world with cars that get driven if you can do it, then epoxy only is ideal. I know Shine feels the same as I do on this.
 
I tried the epoxy only Koolaid. Didn’t care for it in terms of sanding, efficiency from a time perspective, and cost effectiveness. I’ll stick with poly aka the devil’s primer.

Think about what you’re saying Chris. Urethane primer shrinks for me because I abuse it but poly chipped for you because it’s chit….

I’ve been using poly for many years on probably 25 builds. Not one customer has come back to complain of chipping paint. A small sample size for sure but good enough for a backyard hack like me… :)

Where the heck is OJ when we need him? :)

Don
 
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dhutton01 said:
Think about what you’re saying Chris. Urethane primer shrinks for me because I abuse it but poly chipped for you because it’s chit….
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Not at all what I'm saying Don. I wasn't making any specific reference to you, just my observations about urethane and poly. I was sharing the chipping as an example. And FWIW it only chipped because there was poly on it. I feel certain of that. I have come to really like epoxy and that's my preference and what I think is best. You feel otherwise. No problem. But I will continue to share what I feel. It's not an attack against you.
 
The only people who use polyester primer are those who lack metal working skills.

Those poor people.
 
MJM said:
The only people who use polyester primer are those who lack metal working skills.

Those poor people.
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I'm so poor I need to use filler.
I wish I had started learning when I was 20 rather than 55. I must say, however, I will need way less filler than was on the car when I got it. it looked more like drywall than filler in some areas.

-----
Emil
 
dhutton01 said:
If only I could afford a shiny hammer like the one you have Mike. I could crank out multiple award winning killer builds just like you…. :p

Poor Don
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This is my hammer. There are many like it, but this one is mine.

My hammer is my best friend. It is my life. I must master it as I must master my life.

My hammer, without me, is useless. Without my hammer, I am useless. I must strike my hammer true. I must hammer flatter than my competition who is spraying polyester primer trying to be better than me. I must have straighter panels than others without using the devils primer.

My hammer and myself know that what counts in auto restorations is not the shiny hammer, more the sound of metal stretching, but how the hits produce flatness, straightness in the pursuit of perfection.

My hammer is human, even as I, because it is my life. Thus, I will learn it as a brother. I will learn it's weakness, its strength. I will guard it against the ravages of weather and damage as I will ever guard my legs, my arms, my eyes and my heart against damage. I will keep my hammer clean and shiny. We will become part of each other....we will.

So be it, until all damaged panels are flat and straight, I will never use polyester primer. The devils primer.
...................................................:p...................................................
 
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dhutton01 said:
I see a lot of high end shops using polyester aka The Devil’s primer in six figure builds. More using it than not using it. Rust Defender is used extensively by Corvette restoration shops and was even used on the SPI cover car built by Ken Sungela….

Even my brother from another mother Charlie Hutton uses it… :p

Don
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Don, we usually do polyester primer on our first prime. I always like to guide coat sand it down 100/180. After this two rounds of sanding we generally see a lot of that polyester coming off and filling in as needed. We have been using a rm 2k primer that we have had great results with but always like to let things dry out a month or so before we do final finish work.
 
Evil_Fiz said:
I'm so poor I need to use filler.
I wish I had started learning when I was 20 rather than 55. I must say, however, I will need way less filler than was on the car when I got it. it looked more like drywall than filler in some areas.

-----
Emil
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I too wish I had learned how to do auto body work at a young age. I had to take a crash course here on SPI to learn what I know today. I couldn't have done what I've done without the members here on SPI.

All the credit goes to SPI members for the results I've achieved up to this point.
 
MJM said:
I too wish I had learned how to do auto body work at a young age. I had to take a crash course here on SPI to learn what I know today. I couldn't have done what I've done without the members here on SPI.

All the credit goes to SPI members for the results I've achieved up to this point.
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I'm right there with Emil, I'm late to the body work game and have much to learn. Totally agree that SPI forum is hands down best resource on the Internet.

Unfortunately it looks like using poly primer is as much a personal preference as anything (Crash said as much on the other thread).

At this point I think I am going to induce this next layer of epoxy overnight, double coat it then block and see where I stand. Nothing like kicking the can down the road.
 
Joe VanNus said:
Don, we usually do polyester primer on our first prime. I always like to guide coat sand it down 100/180. After this two rounds of sanding we generally see a lot of that polyester coming off and filling in as needed. We have been using a rm 2k primer that we have had great results with but always like to let things dry out a month or so before we do final finish work.
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Hi Joe. I was hoping you’d chime in with your experience at Dutch Boys. That's pretty much how I use the poly primer. First prime after filler work (I spray a coat of epoxy before the poly) and most of it ends up on the floor. I don’t keep 100 around so I usually use 80/150. Then a coat or two of epoxy followed by Turbo 2k to refine the poly scratches.

Don
 
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