The Ford Barn

Mitch · 11-25-2011, 11:55 AM

I'm studying using this line of paint and noticed there is a polyurethane primer and epoxy primer (I have used DP40LF epoxy). What is the difference?

Right now I'm finishing sandblasting the body and will be applying first coats of primer followed shortly after with the primer surfacer coats.

BRENT in 10-uh-C · 11-25-2011, 12:28 PM

Mitch, much of this is terminology verbiage now. To start with, Essential ESU line is the fairly new product that will be shortly replacing the Concept DCC paint product line. I/we have not changed over to the ESU line of substrates because we are still using the MP line however we are starting to shoot some of the ESU finishcoats with favorable results.

With regard to the word "primer", the basic jest is that the Epoxy is a thin "stick-to-everything" substrate designed to go over bare sheetmetal that will promote adhesion for whatever substrate is to be applied next over the top. The downside is that an epoxy generally does not sand well, and it is very thin. If a bodyman is going to install a new fender that may (-or may not) be powersanded, then this is a great product option as light scuff sanding is all that is necessary to get mechanical adhesion. A polyurethane generally has more solids meaning it is a better product to be used as a surfacer, --or for leveling (blocksanding). Urethane primers generally sand much better/easier too.

There used to be some hype that you should use an epoxy first under a urethane ...especially if there was going to be some length of time between the spraying and the bodywork phase however that is not necessarily the case any longer. Now PPG is actually recommending that all bodywork fillers be applied directly over the epoxy primer. Since what we generally do is outside of the mainstream of collision work, their product recommendations are often written where it is confusing to the Restorer. Having a PPG rep or attending their schools is about the only way to learn "the other information" that they don't print. In your case, you will be OK with whichever product you choose however in an effort to save money from needing to stock both products, I would go with the higher-build urethane primer.

Craig Lewis · 11-25-2011, 03:07 PM

Brent, excellent briefing on PPG primers.
Good to hear that the ESU finish coats are working OK for you.
Q? ... have you any input on how well it wet-sands & polishes?

Kevin in NJ · 11-25-2011, 04:41 PM

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The case of epoxy over filler or the other way around is something that needs a hobby perspective.

The key in either case is proper surface prep for the product being applied is critical.

From a hobby perspective you need to get metal protected. Epoxy is a great coating that seals out moisture and bonds well. Fillers bond well but do not seal well, in fact they can absorb moisture.

So from a hobby perspective, you could lay out a coating of filler and find out family gets in the way. Six months later you get time to continue working on the project. In the mean time you had 4 months of 92% humidity and then changed to condensing humidity (the surface got wet every night). So now you have filler that is wet next to bare metal. So getting a panel in epoxy sealer then laying in the filler may make sense for protecting the metal.

The problem with laying out the epoxy is it does not like to be sanded once it gets hard. If you read the directions, they usually tell you to sand cured epoxy and then lay down a fresh coat. During the recoat window (when the epoxy is still curing) you can put down the next layer.

The owner of SPI (Southern Polyurethanes) told me that his epoxy has a long recoat window. During the recoat window he tells me the surface has microscopic "holes" that the bondo type fillers can attach. He advocates epoxy first then filler with his products. His products are made with the hobbyist in mind.

Filler direct to metal is what a body shop needs to do to make money. Works fine lasts a long time. Just may not be the best for you in your project.

It all comes down to understanding the stuff you are using. They have their purposes and how they have to be worked. Take some time to look up the tech sheets and know how to apply the product.

You are justified in feeling confused. There is a lot of bad word of mouth info from 'professionals' and the directions do not always make sense. I took a couple of years to piece together how paints work. Fortunately, SPI is willing to talk about how the paints work and you can find out stuff on the net if look hard.

11-25-2011, 11:55 AM	#1
Mitch Senior Member Join Date: May 2010 Location: Dayton, Ohio Posts: 182	Delfleet Essential primer I'm studying using this line of paint and noticed there is a polyurethane primer and epoxy primer (I have used DP40LF epoxy). What is the difference? Right now I'm finishing sandblasting the body and will be applying first coats of primer followed shortly after with the primer surfacer coats.

11-25-2011, 12:28 PM	#2
BRENT in 10-uh-C Senior Member Join Date: May 2010 Location: Eastern Tennessee Posts: 11,513	Re: Delfleet Essential primer Mitch, much of this is terminology verbiage now. To start with, Essential ESU line is the fairly new product that will be shortly replacing the Concept DCC paint product line. I/we have not changed over to the ESU line of substrates because we are still using the MP line however we are starting to shoot some of the ESU finishcoats with favorable results. With regard to the word "primer", the basic jest is that the Epoxy is a thin "stick-to-everything" substrate designed to go over bare sheetmetal that will promote adhesion for whatever substrate is to be applied next over the top. The downside is that an epoxy generally does not sand well, and it is very thin. If a bodyman is going to install a new fender that may (-or may not) be powersanded, then this is a great product option as light scuff sanding is all that is necessary to get mechanical adhesion. A polyurethane generally has more solids meaning it is a better product to be used as a surfacer, --or for leveling (blocksanding). Urethane primers generally sand much better/easier too. There used to be some hype that you should use an epoxy first under a urethane ...especially if there was going to be some length of time between the spraying and the bodywork phase however that is not necessarily the case any longer. Now PPG is actually recommending that all bodywork fillers be applied directly over the epoxy primer. Since what we generally do is outside of the mainstream of collision work, their product recommendations are often written where it is confusing to the Restorer. Having a PPG rep or attending their schools is about the only way to learn "the other information" that they don't print. In your case, you will be OK with whichever product you choose however in an effort to save money from needing to stock both products, I would go with the higher-build urethane primer. __________________ . BRENT in 10-uh-C . www.model-a-ford.com ...(...Finally Updated!! ) .

11-25-2011, 03:07 PM	#3
Craig Lewis Senior Member Join Date: May 2010 Location: Parksville B.C. Canada Posts: 880	Re: Delfleet Essential primer Brent, excellent briefing on PPG primers. Good to hear that the ESU finish coats are working OK for you. Q? ... have you any input on how well it wet-sands & polishes?

11-25-2011, 04:41 PM	#4
Kevin in NJ Senior Member Join Date: May 2010 Location: South East NJ Posts: 3,398	Re: Delfleet Essential primer Sponsored Links (Register now to hide all advertisements) The case of epoxy over filler or the other way around is something that needs a hobby perspective. The key in either case is proper surface prep for the product being applied is critical. From a hobby perspective you need to get metal protected. Epoxy is a great coating that seals out moisture and bonds well. Fillers bond well but do not seal well, in fact they can absorb moisture. So from a hobby perspective, you could lay out a coating of filler and find out family gets in the way. Six months later you get time to continue working on the project. In the mean time you had 4 months of 92% humidity and then changed to condensing humidity (the surface got wet every night). So now you have filler that is wet next to bare metal. So getting a panel in epoxy sealer then laying in the filler may make sense for protecting the metal. The problem with laying out the epoxy is it does not like to be sanded once it gets hard. If you read the directions, they usually tell you to sand cured epoxy and then lay down a fresh coat. During the recoat window (when the epoxy is still curing) you can put down the next layer. The owner of SPI (Southern Polyurethanes) told me that his epoxy has a long recoat window. During the recoat window he tells me the surface has microscopic "holes" that the bondo type fillers can attach. He advocates epoxy first then filler with his products. His products are made with the hobbyist in mind. Filler direct to metal is what a body shop needs to do to make money. Works fine lasts a long time. Just may not be the best for you in your project. It all comes down to understanding the stuff you are using. They have their purposes and how they have to be worked. Take some time to look up the tech sheets and know how to apply the product. You are justified in feeling confused. There is a lot of bad word of mouth info from 'professionals' and the directions do not always make sense. I took a couple of years to piece together how paints work. Fortunately, SPI is willing to talk about how the paints work and you can find out stuff on the net if look hard.