Technical Difference in Primers

Sic, most painters will have a certain preference, as that is what they know and like to use, or just because it is the brand the shop uses. Any of the major brands' hi-build will be fine. Myself, I like the convenience of one product for all. But I've used Sikkens hi-build for a car that needed a bit more than usual filler, and Featherfill on Vettes. Even used Evercoat's urethane on a car that was a very budget minded build. As long as you don't use incompatible chemistries (etch and epoxy) you should be fine.
It's good to have someone like Paint Guru who has used/tested different brands and chemistries to sort out the differences most regular painters wouldn't have the opportunity to compare.

 

Like chopolds said you can build high build primers in any technology but I will say this, look at my explanation of solids content on the rattle can paint job Tech thread. There is no law regarding what is a standard for "high build ", I personally think higher solids content is a true measure of high build. Now the downside to this story lol. 2 years ago I went our chemist and told him let's build a direct to metal urethane primer that you could convert to a sealer as well. But let's make it so thick and high in solids that it almost will not pour out of the can. We built it, biggest flop ever it was so high in solids people thought it was going bad, then when you convinced them that's the way it was then they would mix and reduce and still put the same amount of coats as they did their old piss primer. So they went from putting 3.5 dry mils to about 10 mils so of coarse it took forever to dry and forever to sand texture out. I had people tell me it was junk so I took it back, took 1 quart of primer out and replaced with thinner, took back to them and they were happy. OK I know I just went way off topic so....

My recommendations for what you have for a diy guy is this: spray 2-3 full wet coats of epoxy over the bare metal. Let it dry for a couple of days. Sand the entire vehicle with 180 -220 grit abrasive. Degrease the vehicle and spray a high build urethane primer, If you want your primer to block sand easy.
The best practice would be to strip all the old Paint off to bare metal and build with epoxy. But there is nothing wrong with the urethane. That's what most body shops do every day.

 

Paint Guru, You have opened up a never ending thread here,lol. So , urethane is a safe high build with a lacquer top coat ? Sounds scary to me. Would it just be wiser to go lacquer all the way.

 

Great info & thanks for the tutorial, Paint Guru.
As an old schooler never venturing past lacquer & acrylic enamel, this thread has my full attention.
Appreciate the explanations in terms that us DIYers can grasp, thank you. Great thread.

 

No its actually safer to do lacquer over most any 2k product. The reason is lacquer primer can be softened back into a liquid state regardless of how long it's been on there. And with lacquer Paint comes lacquer thinner mixed in it. So if the lacquer topcoat is sprayed heavy or wet, you allow the solvents in the topcoat to soften the primer and possibly create loss of adhesion, or paint blistering. This also happens with any Paint going over lacquer primer, they all have solvents that will soften the lacquer.

Try this. Spray lacquer primer. Let it set for 2 days 2 weeks doesn't matter then take a squirt bottle with lacquer thinner (not clean up thinner) and spray a wet heavy coat over the lacquer . Let it sit until you start to see it evaporate then take a rag to the primer. What you will see is the lacquer primer going back to liquid and this is exactly what happens when lacquer topcoat sits on there out of your spray gun.

You can make lacquer primer work. It's still used today. I have sold 2 gallons this morning as a matter of fact. But if you ask me to spec a project where I have to cover the liability for any Paint failure - myself, the paint company, our resin suppliers no one will spec lacquer any where in the process. Not to say it won't last on your car but it's not superior to most any other Paint technology our there for metal and plastic refinish.

 

We did one about 8-9 years ago but back then it was really only evercoat, transtar, and some other brand. I can't remember the brand but we mixed in small cups and just sawed in half to see the amount of air pockets once cured. Transtar had the least but what does that really prove? My personal favorite polyester primer is USC 300-1. I have a quicky Paint Shop I sell that to, and it sands great with 400 grit, which surprised me. And it retails for around $75-$80 gallon.

I might try that out of curiosity. We don't manufacture any, but I sell 2 brands and a good friend of mine is the factory Rep for upol so let's get some freeby stuff coming.

 

Light scuff of the self etch, degrease and tack off then Spray with a urethane primer will be fine.

 

You could use epoxy or urethane. If you don't like the sandability of the epoxy, scuff and spray with urethane.

 

Thanks.

I like the U pol but the texture kills me. That's a bunch of product and labor to sand off before a surface develops.

 

Try reducing the polyester 5-10 percent, or you can buy a cheap 1 qt pressure pot and you can control the finish more so with thicker products with that. Just put a short hose on it.

 

PG,
I have a partially stripped to bare metal project. If I rattle can the bare metal primer areas with etch primer should I then shoot with Hi-Build Urethane (MaxFill)? Will that be OK to prevent rust and to layer the work up for final blocking? What should come next; sealer or....? I think on the next project I'll just shoot Epoxy as, if I understand this correctly, it will cover bare metal and old coatings the best. Correct? Thanks for helping us all out. You truly are a "guru".

 

What type aerosol are you going to use on bare metal?

 

GP,

Great informative write up! So for my 28, I’ve taken the exterior down to bare metal using a combination of sanding/grinding & wire wheeling. It was blasted by a previous owner quite some time ago and left exposed to the elements, so this was not an option for me. I was afraid of the sheet metal thinning out too much.

With the small traces of rust that still remain; would I be safe using an epoxy over top of this at this point? Would you be comfortable doing this if this was your car? This is by no means a high dollar show car, I just want something that’s going to hold up and work within my budget. I know there are people out there that’ll say you must remove ALL traces of rust (obviously this would be best), but for my case I just want to know if this is something that’s relatively safe to do. I guess rust needs oxygen so given that epoxy seals so well, I’m thinking I should be fine. Then again I’m no expert.

 

Those jobs that need blasted but don't get it bother me too.

 

Yea I would take 180 sandpaper with a sander get off what you can, degrease with vm and p naphtha (wax and grease remover) and epoxy. Remember you need to put 2-3 good wet coats, and I would feel comfortable with that all day.

 

That's what I was hoping to hear. You rock!

 

SEM brand.

 

Sem self etch?

 

Yep. It is available here in Canada. I do have a gallon of MaxFill high build urethane primer and a gallon of Omni MP 802 multi pulse primer which I can returned if it is redundant.

 

This thread is chock full of win. Thanks in spades to the OP for sharing this wealth of info!

 

When you're sanding, make sure to sand all the areas where you used the wire wheel. A wire wheel leaves a glazed surface that can cause problems with paint not sticking, but a quick pass with the sander will give it enough tooth to hold the primer.

 

I personally don't know much about the omni, I am really not a fan of big Paint companies 2nd tier products. You could etch with sem then put urethane on top. Read the instructions on the can on top coating. But typically you can spray 1 medium coat then tack off and topcoat with urethane.

 

So spray the etch on the bare metal areas and then the high build, correct?
Do I need the MaxFill high build and the Omni general purpose primer? Would I spray with the general purpose after I finish blocking the high build, it can be used as a sealer as well. Sorry for all the questions but previous advice from non-gurus have confused me so much I'm thinking about taking up stamp collecting as a hobby instead!

 

LOL I know how you feel, but if you ever get to that point where you feel stuck in the paint process just send me a message I can walk you through step by step.

So after you etch, use your MaxFill from there on up and return the omni. If you get done blocking and then see other areas that need attention work those areas and continue use of the MaxFill until you are ready for top coat.

Who makes MaxFill?

 

Thanks for the directions". MaxxFill is made by Five Star Autobody Products.

 

Ok, year 5 Star isn't a manufacturer. They are a large private label company. ..just FYI

 

Who makes it for them? I presume the quality is OK?

 

They take bids every so many years, but yea it's always reputable companies.

 

Thanks PaintGuruMan (kinda like a super hero).