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Discussion Starter #1
I wasn't sure whether to ask this on Paint Systems: A tempest in a Teapot, or start my own.

For starters the photo was somewhat exaggerated by upping the contrast in PhotoShop, but in any event you can feel the 'grain', so obviously it has to be sanded out/down.

Often I get a high fuzzy build up in what I term 'crotches' on the body as in where a fender goes from a curved panel to a straight one. However, this is obviously on a basically flat surface.

My plan, for now, is to go over the entire car using a file with 220 or 180 to bring all of this down and to correct several low/high spots. Yes, of course it really shouldn't need it at this stage, but it does.

Most likely I'll have to reprimer and want to avoid this mottling next time around. This is PCL high build polyprimer over PPG's DP50LF. Yes, it was thoroughly dry before applying the high build.

I make a great effort to keep the air filters - one near the compressor and one at the other end - drained. I'm careful about cleanliness. I use a Sata primer gun. I thin with a fairly small dollop of acetone.

I'm certainly open to any suggestions, including using another brand of high build primer. However, PCL is virtually the only high build primer available at paint/bodyshop supplies in this area.

I need to get this car painted, but obviously I won't until I can resolve this issue.

Biba
 

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How much psi at the gun? Maybe too high?
 

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Hi Biba,

You have my deepest sympathies! I hate it when poly textures up. Good news is it will save you some time with the filler, bad news is sanding poly texture sucks!

Some tips:

The problem is comon on polyester fillers to get a huge amount of texture if it doesn't go on just right. The gun makes a big difference in the texture, you need a huge tip to get it on smooth. What size tip are you using for your polyester primer? I use a Sata KLC HVLP with a 2.1 tip and it makes a huge difference. Sata just came out with a KLC P specifically for polyester priming--haven't tried it, but it might be worth it.

I have never used PCL, but I have shot Sherwin and PPG's poly, I can't imagine that it is that different. It is more expensive, but I do like Sherwin's poly, it goes on smooth.

In the end, buying the right gun saved me weeks of sanding work. I really think the big bore priming gun paid for itself in the first use. As always, your mileage may vary!

Cheers,

Mike
 

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Discussion Starter #4
Regarding air pressure, since Sata's are so easy to adjust, I've tried spraying at different settings and quite frankly I have no idea what the actual pressure is at the gun. I do purposely adjust the regulator high, so I can then dial it down until 'it seems right'.

Mike, boy did I do a brain fade. I was positive my Sata KLC RP was a 1.8 tip and never thought anything else about it. My excuse is teh 6 looks very much like an 8, so it's a 1.6., and yes my close-up eyesight is pretty good. While not inexpensive I'll get a 2.1 tip.

I paint inside, but primer outside...on weekends. This is an industrial park and is pretty deserted then. What I'm leading up to is often I've primered very late in the afternoon. Consequently I do feel I don't let it dry long enough before applying a second coat and consequently, especially in what I call the crotches, it's not nearly dry and that is why I end up with a Very rough texture in those areas.

About what percentage of acetone do you add on say a 75 degree day, in the shade or inside? And how many coats do you apply in one 'sitting'? I hate cleaning a gun in the middle of a job so if I wait long until the primer is only slightly damp to the touch, the primer in the gun will have kicked in.

I don't understand how the textured primer is going to save me time with the filler. Or are you suggesting I put on a thin skim of polyester finishing putty in the textured area?

Biba
 

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Biba, I'll offer some long ago advice passed on to me by a master of his craft: Do you think you might be having a chemical reaction? Tony was always very catholic about making sure he used the same thinners, primers, and paint from the same manufacturer. He absolutely did not like mixing products, regardless of claims of compatability. Just a thought.
 

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Discussion Starter #6
Jim, good point, but I've used the combination of the PPG epoxy primer under the PCL high build primer and have had some problems with mottling but nothing like this. If it was all over the car, I'd definitely have to look into the chemical reaction possibility. PPG's DP50LF epoxy is almost a standard for many body men/painters,especially the good ones.

Mike, I've ordered a 2.0 nozzle set from Sata. Actually from a local dealer, who had to order it from his jobber who had to order it from Sata. Sata won't sell direct. Jackie, Sat's tech person advised against the 2.5 polyester nozzle set. She even agreed she'd switch me to the 2.5 if I wasn't happy with the 2.0. She agreed my 1.6 was not a good choice for polyster (that's what you get from buying on the Internet). Because there's people like me who buy a gun on say eBay, then need parts such as nozzle sets, is why they won't sell direct. So, I'm paying retail ($119) for the set.

I am also going to let the primer dry longer, even if I have to stop and clean my gun between coats. Sata recommends at least 25 minutes between coats. With high build, I'd guess the primer in the gun has kicked in pretty well.

Biba
 

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Biba, being your are primering outside, is it possible the temperature is to cool and the primer is not flashing off fast enough? If you are getting mottling, I was thinking the body might not be warm enough, and you are getting a build up in certain spots. I would be careful of wrinkles where the primer can run together or sag in spots. I would add a air pressure guage at the fitting just before the gun so you know exactly what pressure is applied at the gun, as you might be also losing air pressure if your hose is to long from the compressor. I also added a water trap just before the gun to catch any moisture from the hose. Just my 2 cents for what its worth.
 

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Hi Biba, not sure what happened, I replied last week on here, but it didn't take. So here is a repost of my response.

About what percentage of acetone do you add on say a 75 degree day, in the shade or inside? And how many coats do you apply in one 'sitting'? I hate cleaning a gun in the middle of a job so if I wait long until the primer is only slightly damp to the touch, the primer in the gun will have kicked in.
I looked up your primer's data sheet on the Internet. It has different specs that Sherwin Williams 21, which is what I have used recently. Sherwin has a pot life of 45-60 minutes. You can thin it with up to 10% acetone. I don't like to thin it more, as it starts to run. The Sherwin stuff is easy to spray without a lot of texture.

What I do is, go around the car and shoot one two light coats on the areas I know are a little low, let those flash (although generally by the time I walk around one side of the car to the other it has already flashed). Then I apply one wet coat to the whole car and allow to flash for 5-10 minutes. Then I apply one to two addional wet coats as needed allowing 10-15 minutes flash time between second and third coats.

I mix the small cups individually, and I sometimes rinse the gun with acetone between cups if the gun is clogging. But generally, my goal is to just shoot quickly and move on.

The coats when dry are only 2-4 mils thick. Three coats works out to 6-12 mils thick when dry. You may be putting too much on.


I don't understand how the textured primer is going to save me time with the filler. Or are you suggesting I put on a thin skim of polyester finishing putty in the textured area?
That was a bad joke. I just meant that when you sanded off the mottling, you would still have some left in your valleys. Although, serisouly, I frequently have to add more than one application of poly primer before I am happy.

I generally buzz the texture off of polyester with a DA and a soft foam pad and 180-240 dry paper. I am too lazy and polyester is too hard to sand the texture out of by hand. I still use guide coat so I don't lower the valleys. Sometimes I will even spray more poly on the areas that look really low before I start block sanding the whole car.

Jim, good point, but I've used the combination of the PPG epoxy primer under the PCL high build primer and have had some problems with mottling but nothing like this. If it was all over the car, I'd definitely have to look into the chemical reaction possibility. PPG's DP50LF epoxy is almost a standard for many body men/painters,especially the good ones.
I don't think this is a chem reaction. I have had similar issues when I have a bad application of poly on bare metal.

Mike, I've ordered a 2.0 nozzle set from Sata. Actually from a local dealer, who had to order it from his jobber who had to order it from Sata. Sata won't sell direct. Jackie, Sat's tech person advised against the 2.5 polyester nozzle set. She even agreed she'd switch me to the 2.5 if I wasn't happy with the 2.0. She agreed my 1.6 was not a good choice for polyster (that's what you get from buying on the Internet). Because there's people like me who buy a gun on say eBay, then need parts such as nozzle sets, is why they won't sell direct. So, I'm paying retail ($119) for the set.

I am also going to let the primer dry longer, even if I have to stop and clean my gun between coats. Sata recommends at least 25 minutes between coats. With high build, I'd guess the primer in the gun has kicked in pretty well.
I had this problem once before when using too small a tip with a PPG Omni polyester primer. I think it is an application problem, and I think you are on the right track. Let us know how it goes with the new gun.

Best,

Mike
 

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Discussion Starter #9
Christopher, I believe you have something there regarding spraying when it is too cold. However, since it's been getting colder even here (distant mountains covered in snow), I'll be primering in the sun and even then, if I have to wait a bit longer I will.

Mike, I have to admit at this point the mottling isn't all that much of a problem since the car Really needs lots of sanding, and most likely a bit of filling here and there. I'm not sure what a DA is but I've been using a combination of a six inch orbital sander with 120 and a 17" file with 150. Of course there are places where only a smallish foam sanding pad (I have them in lots of shapes) will work. When I get to the final stage of the primer ready to be painted (not sure now if I'll ever get there - I've been on this car for a very loooong time) I'll do a final wet sand with either 400 or 500. Sound reasonable to you?

As it turns out this primering is acting a lot like a guide coat. I sure hope after the next primer light blue/yellow filler don't show through. Trust me, you would not have wanted to inherit this job.

You're sure the Sherwin Williams primer isn't actually house paint? Yeah kidding, but not normally where I'd ever think to go to get automotive primer. But I'm certainly game to try a different polyster primer - if it comes in a red oxide color.

Since I've just resolved a 0 oil pressure situation with my daily driver Alfetta GT, I'll be back on the '58 Spider Veloce with a vengence since I want to someday get it out of my life.

Don't put your Underwood typewriter away, I might still have more questions.

Biba
 

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Discussion Starter #10
Mike, I just went to Sherwin Williams website and while I was kidding before about the primer being house paint (this is what I keyed in at their site) "Sherwin Williams 21 auto primer" and got: "form function…and plans frequently change. So he called for a standard automotive body filler where necessary to smooth surfaces, then one brushed…then one brushed-and-rolled coat of Sherwin-Williams KemBond Automotive primer, followed by two brushed-and-rolled coats of Sherwin-Williams Industrial…"

Mind ringing them up and telling them they have "Sherwin Williams 21 auto primer"? Apparently they are unaware of that fact. Yes, I'm kidding (sort of) but except for what they call marine and industrial, they virtually have no automotive section on their website.

Don't think I'll be rolling on automotive primer.

Yeah, being a bit pissy, but if a company has a great product, they need to let people know about it.

When googling and on their own site, August 21 was the only situation that number came up when connected to the words 'Sherwin Williams'. "Oh yeah, we might have a quart of that stuff. It's over there with the baby furniture paint."

Biba
 

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Hi Biba,

You need to be on the automotive site: Home: Sherwin-Williams Automotive Finishes Corp. - Automotive Paints.

Here is the web url for the primer:
Products: 21 - Polyester Primer

and here is the datasheet url:
http://www.sherwin-automotive.com/media/pds/English/5208.pdf

For what its worth, the last car I did, I did it this way: Strip to bare metal, then all Metal aluminized filler, then Sherwin polyer primer, then Evercoat Z-Flex polyester filler, then Sherwin SpectraPrime™ SpectraSeal™ Color Surfacer / Sealer (comes in colors and can be used as a primer or a sealer) used as a primer, then Spectra Prime used as a sealer, then base/clear. Of course, sanding between each step. These materials are all expensive, but they are fast and easy to use.

Good luck,

Mike

PS DA= Dual Action Orbital Sander
 
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