Rolling on Primers?

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PostPosted: Wed May 22, 2019 4:00 pm
I've heard guys say they they roll their primers on and found this video on you tube. After watching it, I can't see any reason why one couldn't do epoxy, then poly, and then urethane primer. A friend of mine took his car down to bare metal and then realized he didn't have the equipment or a suitable place to spray. Is there any reason he couldn't do all the prep work by rolling the primers? Seams like it would work fine to me. Maybe he could get it to the final blocking and then rent booth time at a local shop for final paint and clear. Has anyone done this? Also, seems like it would save a lot of material, no masking, and minimal clean up time.

https://www.youtube.com/watch?v=HUx42osTqlw

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PostPosted: Wed May 22, 2019 4:46 pm
It's a technique that was actually recommended to me by a paint company rep, particularly for small repairs as saving time and money on masking and booth time.

I tried it a few times but there is enormous wastage in primer on the roller as well as a lot more work to get the surface, even with a relatively flat roller finish, smooth enough for spraying top coats. Using a 2K primer I also found that a new roller and clean tray was needed for each coat - meaning more cost and wastage. Once the primer on the roller starts to go off the roller doesn't work so well and finish is awful.

I also had issues with aeration and sometimes had to re-spray the primer to get a decent finish without pinholes. It's also difficult to get high build unless done in many coats since each coat thickness is determined by roller nap and rollers that leave a thicker coat also leave a higher surface texture - which just has to be sanded off.

TBH I couldn't make it work well enough for our needs and we went back to spray application. Using the right gun and air pressures can give you very high transfer efficiency and a surface that needs little sanding.
Chris

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PostPosted: Wed May 22, 2019 6:05 pm
Yeah, NFT pretty much nailed the problems that creep up when trying this.... manufacturer's have wet mil thickness rec.s which transfer to the final dried films. Rollers are kind of like squirrel hunting with a grenade launcher. Too much, too fast, too thick and most importantly of all "no atomizing" effect. Pinholes are big problem and you aren't even seeing all of them. I'd leave the rollers to the walls at home.
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PostPosted: Sat May 25, 2019 7:19 am
Rolling is done a lot in the Aircraft industry, But they have it figured out to what works and what doesn't for them. But nobody really cares what it looks like at 50,000 feet, The closest most get to an aircraft at an aircraft terminal is a window at least 100 feet away so you cant see the details of it and a 100 footer looks fine. And yes I have seen huge pieces that have peeled away from flying 500 mph.

It can be done on a car its just a lot more sanding and waist to get it right.
You can even Roll Single stage but here again a lot of sanding and waist to get it flat and then you still have to polish it.

I have seen guys Brush Epoxy on the bottom of cars before as well here again who cares what the finish looks like when your only under there to change oil or grease the chassis.
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PostPosted: Sat May 25, 2019 9:22 pm
The marine industry uses a technique called "roll and tipping" that involves using
a combination of rollers and brushes. The trick is to get the paint at the right
consistency and to work fast to keep a wet edge. Use disposable rollers.

Rolling is best used when you're doing a small project at a time (such as a fender)
and don't want to bother with spraying, or you've stripped a car and need to protect
it from rusting through the winter (and don't have spray equipment). You can roll on
a coat of epoxy primer for protection, and then block it smooth when time permits.
As stated, it's a lot of extra work and your arms will look like Popeye's afterwards...
"If you can't move it, paint it." - U.S. Army

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