Reducing PPG Concept Urethane

JJ and Hank will chime in, but as an amateur now on his 3rd refinish project, the short answers are "effort and repairs". Polyester topcoat (i.e. Prestec/Simtec in these parts) is reasonably forgiving of less than ideal shop conditions, equipment, lighting, and skill. It goes on thick and encourages "color sanding" - sanding out and polishing. And, when the inevitable nicks and dings happen, it's pretty easy to repair, even in the field (e.g.. painting on with a brush or quickly spraying with a preval hobby can). Urethanes on the other hand require pretty much perfect surface preparation - whatever shape the primer is in is essentially what you get in the final coat. It goes on thinner and is harder to sand out without going right through to the primer, which means back to the shop again. And, the stuff is a lot more dangerous to work with in terms of toxicity, requiring a full fresh-air system. Plus, it's harder to repair nicks and dings quickly, though it is quite doable.

I re-did our club's Grob in PPG Concept since it sits tied out mostly year-round, and it's held up very well. Much better than Polyester. But, the quality of the finish in terms of some low spots, a couple of runs, and a few thin spots definitely shows. The good news is that it would be relatively easy at this point (5 years on) to quickly sand off the topcoat, reprime, and get a very good finish. But clubs don't typically do that; they wait until big chunks start falling off, in which case we're back to the really ugly process of sanding off all of the failed primer. Yuck.

p3

On Sunday, January 24, 2016 at 2:16:29 PM UTC-5, Papa3 wrote:
JJ and Hank will chime in, but as an amateur now on his 3rd refinish project, the short answers are "effort and repairs". Polyester topcoat (i.e. Prestec/Simtec in these parts) is reasonably forgiving of less than ideal shop conditions, equipment, lighting, and skill. It goes on thick and encourages "color sanding" - sanding out and polishing. And, when the inevitable nicks and dings happen, it's pretty easy to repair, even in the field (e..g. painting on with a brush or quickly spraying with a preval hobby can). Urethanes on the other hand require pretty much perfect surface preparation - whatever shape the primer is in is essentially what you get in the final coat. It goes on thinner and is harder to sand out without going right through to the primer, which means back to the shop again. And, the stuff is a lot more dangerous to work with in terms of toxicity, requiring a full fresh-air system. Plus, it's harder to repair nicks and dings quickly, though it is quite doable.

I re-did our club's Grob in PPG Concept since it sits tied out mostly year-round, and it's held up very well. Much better than Polyester. But, the quality of the finish in terms of some low spots, a couple of runs, and a few thin spots definitely shows. The good news is that it would be relatively easy at this point (5 years on) to quickly sand off the topcoat, reprime, and get a very good finish. But clubs don't typically do that; they wait until big chunks start falling off, in which case we're back to the really ugly process of sanding off all of the failed primer. Yuck.

p3
Sorta makes me want to ask, "What does does your polisher want to work with?"

I LOVE gelcoat, "heat the crap out of it and load it with wax...". It makes me happy (as well as the wax supplier.... not so much the shop supervisor....).
When I have to hit different coatings (vinyl stickers...."shoot 1st, forget about questions later...fix with monokote", some other paints can be touched but hate heat....sigh....).
I keep saying, "If you want a price on a GOOD wax job, so be it. You want to go around other stickers/paints, PLEASE charge extra...". "Please".

Some finishes are rather easy to get a, "Customer approved, glider happy" result. Trying to "cut in" stickers/different paint, OR, softer finishes sorta ****es off the final polisher. :-(
Since I'm the "end guy", I have to "polish to a price", but what I do is the final result of many steps beforehand.... I can't polish crap (to look really good), but I can make good prep look like crap.
The polisher is the last in the, "Quality to the end user" chain.

On Sunday, January 24, 2016 at 2:16:29 PM UTC-5, Papa3 wrote:
JJ and Hank will chime in, but as an amateur now on his 3rd refinish project, the short answers are "effort and repairs". Polyester topcoat (i.e. Prestec/Simtec in these parts) is reasonably forgiving of less than ideal shop conditions, equipment, lighting, and skill. It goes on thick and encourages "color sanding" - sanding out and polishing. And, when the inevitable nicks and dings happen, it's pretty easy to repair, even in the field (e..g. painting on with a brush or quickly spraying with a preval hobby can). Urethanes on the other hand require pretty much perfect surface preparation - whatever shape the primer is in is essentially what you get in the final coat. It goes on thinner and is harder to sand out without going right through to the primer, which means back to the shop again. And, the stuff is a lot more dangerous to work with in terms of toxicity, requiring a full fresh-air system. Plus, it's harder to repair nicks and dings quickly, though it is quite doable.

I re-did our club's Grob in PPG Concept since it sits tied out mostly year-round, and it's held up very well. Much better than Polyester. But, the quality of the finish in terms of some low spots, a couple of runs, and a few thin spots definitely shows. The good news is that it would be relatively easy at this point (5 years on) to quickly sand off the topcoat, reprime, and get a very good finish. But clubs don't typically do that; they wait until big chunks start falling off, in which case we're back to the really ugly process of sanding off all of the failed primer. Yuck.

p3

P3 has hit a lot of the key points. Polyester finishes hold up pretty well to what we do to them. The glider in my shop now is 34 years old and the original gelcoat finish was still just fine with only minor crazing. It's only getting a new finish(polyester) because the former owner impact modified it.
For someone doing the job themselves on a budget the cost difference is significant. AU like Concept costs about $1700 for the material required for a 15 meter glider versus about $500 for polyester topcoat.
If you are having the job done professionally the material cost difference is just noise.
FWIW
UH

Thanks for all the tips. I sprayed today 4 paint, 3 reducer (instead of two), 1 hardener. It was much better! Im spraying in an I heated hanger, 60-65 degrees. But the extra reducer got the viscosity low enough to make the spraying work well.

On Sunday, January 24, 2016 at 9:57:28 PM UTC-5, wrote:
Thanks for all the tips. I sprayed today 4 paint, 3 reducer (instead of two), 1 hardener. It was much better! Im spraying in an I heated hanger, 60-65 degrees. But the extra reducer got the viscosity low enough to make the spraying work well.

you should be fine with 4:2:1 using concept. make sure the air pressure is set right and that your gun is in good working condition. you CAN add more reducer, or use a higher temp reducer. you could try reducing with DT 885 on your paint job. 885 is slow which is good for minimizing orange peel, just make sure you wait between coats. 870 just doesn't flow as nice in my experience, even when the room is "cold".

if I understand correctly, the warm temp reducer results in less orange peel, correct? Is that because up takes longer to evaporate, giving the paint more time to "spread out". I was using the medium temp, but the high temp stuff may be worth a try. Thanks!

On Monday, January 25, 2016 at 11:27:41 PM UTC-5, wrote:
if I understand correctly, the warm temp reducer results in less orange peel, correct? Is that because up takes longer to evaporate, giving the paint more time to "spread out". I was using the medium temp, but the high temp stuff may be worth a try. Thanks!

your welcome, that's correct. DT885 is definitely worth a...shot. i'll go punch myself in the face now. the smaller the fluid nozzle, the higher the air pressure, and the more runny the paint is, the finer the atomization. that results in smaller particles and more flowing. in addition, the higher temp reducer takes longer to evaporate. be careful adding additional reducer with the DT885. that doesn't mean you can't... it means be careful. otherwise, you'll become a master of sanding out runs. with concept, if you get runs in the paint the runs will appear a very light gray after they are sanded out. ask me how i know.... also, i don't know how experienced you are with spraying, but this comes in handy:

http://www.autorefinishdevilbiss.com...e_Maint%29.pdf

On Monday, January 25, 2016 at 11:27:41 PM UTC-5, wrote:
if I understand correctly, the warm temp reducer results in less orange peel, correct? Is that because up takes longer to evaporate, giving the paint more time to "spread out". I was using the medium temp, but the high temp stuff may be worth a try. Thanks!

That is my experience as I tried to describe in an earlier portion of the thread.
That said, much of the orange peel is a result of less than perfect gun adjustment and technique. Finish paint wants a smaller tip than filler and more attention to adjustments. Big droplets coming out of the gun not fully atomized are not going to be as flat as finer mist.
It takes a long time to become a good painter and most of us get to be good sanders first.
For sand out look at 3m Trizact sanding discs used on an orbital sander. 1500 grit, followed by 3000 grit will make it easier to do a good job. Contact me privately if you want more detail.
UH

On Sunday, January 24, 2016 at 12:32:25 PM UTC-5, wrote:

For acrylic urethane I use a turbine HVLP system which gives a big pattern and has no water in the air. I can't make myself use my $400 gun for polyester topcoat so I do get a few fish eyes in that.
FWIW
UH

I know guys that are serious about painting are particular about
what goes through their guns -- never put primer through their
favorite gun and so on. But what's the rationale for this? It
seems to me that the paint follows such a short path through
the gun that it can't cause any serious wear. At least for
gravity feed guns. Are there other issues?

Jim Beckman

On Wednesday, January 27, 2016 at 7:44:01 AM UTC-5, wrote:
On Sunday, January 24, 2016 at 12:32:25 PM UTC-5, wrote:

For acrylic urethane I use a turbine HVLP system which gives a big pattern and has no water in the air. I can't make myself use my $400 gun for polyester topcoat so I do get a few fish eyes in that.
FWIW
UH

I know guys that are serious about painting are particular about
what goes through their guns -- never put primer through their
favorite gun and so on. But what's the rationale for this? It
seems to me that the paint follows such a short path through
the gun that it can't cause any serious wear. At least for
gravity feed guns. Are there other issues?

Jim Beckman

i have a favorite gun, i'll put primer and topcoat through it. it just needs to be thoroughly cleaned. if there is residual junk in the gun, even stuff around the cup lid, it can end up in your topcoat. thats probably why most people are weird about it. the primer itself has no negative effects on the guns ability to shoot paint.