How to know when to stop practicing and start painting

R

robking

Promoted Users
Hey folks, it's finally time for the rubber to hit the road. For practice I had an old trunk lid that was pretty flat, sanded it to metal shot two coats of unreduced epoxy then wet sanded at 600 to get a smooth(ish) starting surface.
  • Motocryl SS
  • LPH400 1.4 silver
  • 20 PSI
  • Three coats total, 10 minutes flash between coats
  • Gun 1 turn in on first coat, then wide open on subsequent passes
  • 75% overlap
  • Air temp 70 degrees
Paint is going on plenty thick I think, one small sag in corner where I doubled up a little much.

For the real panels, the plan is 4 coats and gentle cut/buff.

Trying to convince myself that my gun technique and settings are such that I can get the paint on well enough that it will clean up with cut/buff. Not show quality but good enough where someone doesn't say "you did that yourself didn't you" right out of the gate. :)

The trunk lid was oriented vertically as I wanted to know that I'm not laying it on too thick and getting lots of runs. I only had the single sag, however it's not exactly glass smooth. Hopefully these are clear enough (full pic and cropped to show what I mean) for you to get an idea of what I've got.

Any advice is greatly appreciated!

PXL_20250604_134102003.jpg

Zoomed in

PXL_20250604_134102003_cropped.jpg
 
Raise the pressure at the gun to around 23-24 psi. Tech sheet suggests 21-29 psi.

I know it states 8-10 minute flash time between coats, but it may take a bit longer when you are spraying it on so heavy.
 
Last edited:
'68 Coronet R/T said:
Raise the pressure at the gun to around 23-24 psi. Tech sheet suggests 21-29 psi.

I know it states 8-10 minute flash time between coats, but it may take a bit longer when you are spraying it on so heavy.
Click to expand...

Thanks, that's an interesting point on the suggested air pressure that has always slightly confused me about this LPH400. Tech sheet that comes with it states that pressure should be 14-18 PSI to achieve 10 PSI at the air cap, where my DeVilbiss guns call for more like 28-30 for 10 at the cap. So when the paint vendor gives an air pressure like that, seems like that would be relative to the gun and it's characteristics.

That said, I've read on here many times that 10 at the cap is to meet regulations, if it sprays better at 24 I'm all for it.

I also found another small run, so I definitely was putting it on there. I was purposefully moving slower than when I shot the backs of the hood/trunk etc in hopes of getting less peel. Feels like I may have overdone it. At any rate I'll push the flash time out to closer to 30. Since the recoat window is 12 hours I would think you can get away with quite a bit of flash time.

Jim C suggested on previous thread of mine to start at 1500 once I have my four coats on, I think I will give this a day or two to dry and try 1500 to see how easily that peel comes out just to help boost my confidence if nothing else.
 
Increasing the air pressure will reduce the size of the droplets. This will help it to lay down better and it should flow out more evenly as well.
The 10 minute flash time may work in this scenario.

The distance from the panel is also important. The LPH400 works best at 4-6" from the panel. Keep your distance and speed consistent and you will notice a difference with the increased air pressure.

After you spray a coat, watch to see it flashing off. You can also touch a spot on the masking tape to be sure it doesn't stick to your glove. No stringing and you should be good to apply another coat.

Spraying single stage is different than spraying base coat. It is more like spraying clear coat. Hopefully the pros and more experience SS users will chime in soon
 
I’ve sprayed quite a bit of Motocryl with an LPH400 and silver cap. Your fluid is out too much; spray more like 3 turns out. This is one of the reasons you’re getting runs and sags.

The other reason is you need to increase your air pressure. I spray closer to 28-30 psi.

As mentioned, hold the gun close to the panel (4”), overlap 75%.
 
robking said:
Jim C suggested on previous thread of mine to start at 1500 once I have my four coats on, I think I will give this a day or two to dry and try 1500 to see how easily that peel comes out just to help boost my confidence if nothing else.
Click to expand...
It might work for you starting with 1500.
I thought the same but 1500 didn’t really remove my peel. It did make it easier to get a gloss but…
OJ said it would take 1000 to get the peel close to flat….and it worked. Then I did like JC said
Leave 20% with 1000, then do the 1500 and so on.
Yours looks better off the gun than mine.
 
i almost always start with 1000 BUT there are things that i will just start at 1500 with. typically if i clear, sand with 400 and reclear then the finish will be smooth enough to just roll with 1500. this is with spi clearcoat. ss has always been more difficult for me to sand and buff. i have never used motocryl
 
Lizer said:
I’ve sprayed quite a bit of Motocryl with an LPH400 and silver cap. Your fluid is out too much; spray more like 3 turns out. This is one of the reasons you’re getting runs and sags.

The other reason is you need to increase your air pressure. I spray closer to 28-30 psi.

As mentioned, hold the gun close to the panel (4”), overlap 75%.
Click to expand...
Thanks Lizer, as you and 68 said I definitely need to bump the pressure. I was already pretty sure I had fluid a bit high. Basically this test panel was me playing with increasing fluid assuming more fluid equals less peel. Going to shoot the door exteriors in the morning, and will pay close attention to how it's laying down before moving to subsequent coats.
 
robking said:
Thanks Lizer, as you and 68 said I definitely need to bump the pressure. I was already pretty sure I had fluid a bit high. Basically this test panel was me playing with increasing fluid assuming more fluid equals less peel. Going to shoot the door exteriors in the morning, and will pay close attention to how it's laying down before moving to subsequent coats.
Click to expand...
Be careful with that much fluid, you’ll get runs on vertical surfaces. Plus the risk of solvent pop hosing it on. YMMV….
 
Worn Out Welder said:
It might work for you starting with 1500.
I thought the same but 1500 didn’t really remove my peel. It did make it easier to get a gloss but…
OJ said it would take 1000 to get the peel close to flat….and it worked. Then I did like JC said
Leave 20% with 1000, then do the 1500 and so on.
Yours looks better off the gun than mine.
Click to expand...
So I found that all I had handy was some 2000 wet/dry and decided to try blocking dry using both a dura-block and small black diamond block. Both actually took that texture out quickly. So hopefully with better atomization and little less fluid it will be even flatter.
 
Tungsten said:
Your doing it wrong!First you screw up a paint job or two.Sand it all off and doit again.
Then you practice on a spare panel.Its just how it supposed to be.
Click to expand...

Well, I must be on the right path now, cuz I totally screwed the pooch this AM! ;)

Did 10% reduced epoxy sealer last night, got up this AM and denibbed a few spots, cleaned up with sprayway and let it sit for an hour. Mixed up my paint (enough for 4 coats, first mistake), tacked and shot the first coat at 26 PSI and 3 turns out. Did my best to maintain 4" and 75% overlap (feels like your hardly moving between passes).

First coat, paint laid down *ok* but not any better than I saw at 20 PSI and 4 turns to be honest.

Dirt nibs EVERYWHERE.... I don't know what the @%$#%! happened, followed my normal routine (paint suit, wipe hose, etc) but it was pretty bad.

Oh got a run and hose slap for good measure (both on me).

Since had I mixed up so much paint I felt like I had better shoot the rest. Subsequent coats went on about the same, but on last coat it started dry spraying on second door without me realizing it. Even though I had paint left I think the dekups once they are almost empty wont collapse but so far and I pushed it.

So I guess my best bet is to sand this with 600 and start over?

Or load the freakin' thing on a trailer and take it to a painter that knows what they're doing. :(
 
Every once in a while I do a job that looks like I was eating crackers with one hand and painting with the other. Usually it's something that has to be nice. I think sometimes it's static, other times, who knows. All we can do is stack the odds in our favor, but "stuff" happens. On an ordinary job, what you describe might be a candidate for a sand and polish, for something nice, you might want to just re-clear it if the trash isn't visible after sanding.
 
I don’t think you need to start over. Try a quick cut and buff on the worst of it. If that’s not good then maybe sand with 600 and shoot another three coats. This is why I usually advise us backyard hacks buy extra paint… :)
 
crashtech said:
Every once in a while I do a job that looks like I was eating crackers with one hand and painting with the other. Usually it's something that has to be nice. I think sometimes it's static, other times, who knows. All we can do is stack the odds in our favor, but "stuff" happens. On an ordinary job, what you describe might be a candidate for a sand and polish, for something nice, you might want to just re-clear it if the trash isn't visible after sanding.
Click to expand...
I needed that laugh big time, thank you!

I swear it seems the harder I try to reduce the dust and overspray, the worse it gets. Sprayed a lot of epoxy over last couple years and the cleanest jobs were when I just cracked the window (has a filter over it) and opened the garage door a couple inches. No fans running.

The sealer went down fairly clean yesterday, but I had wet the floors the day before then squeegeed them off and let them dry. Feels like a I need to be doing that every time, but man what a pain (I don't want the extra humidity so takes a long time).
 
dhutton01 said:
I don’t think you need to start over. Try a quick cut and buff on the worst of it. If that’s not good then maybe sand with 600 and shoot another three coats. This is why I usually advise us backyard hacks buy extra paint… :)
Click to expand...

Thankfully I took your advice on another thread and did buy extra paint. Due to the hose slap spot, I'm very tempted to sand with 600 and hit them with a couple more coats. Just the exterior of two doors, so won't need a ton of paint for two more coats.
 
By the way, I'm pretty sure this is 100% karma. Met a very nice gentleman over with the weekend with a 55 Belaire, good looking car from a distance but paint was a bit rough. Turns out he had it painted at the local Maaco. I was looking at the amount of peel, wavy body and feeling pretty good about myself at his expense. Except he's out there enjoying his car every weekend, and I'm taking a mulligan after four years of body work.

Karma...
 
crashtech said:
There's a difference between pushing yourself to do better, and beating yourself up. Painting isn't easy. There are some individuals out there that have a natural talent, the rest of us have to work our asses off and practice a lot. You'll get there!
Click to expand...

What you said here, I think every novice painter needs to hear. A nice paint job is as much a work of art as it is a skill, and it's pretty presumptuous as a beginner to think you can read a bunch of stuff on the internet and knock it out of the park first try. Thanks again to everyone on here that are skilled in the art for sharing your hard earned wisdom and talents.

Finally got time this AM to reshoot the doors before the heat wave rolls in. I believe the bulk of my issue the first round was using medium hardener and reducer. Looking back it was reasonably cool that morning but humid, compared to when I shot the test panel. Today I used slow/slow (started out a 72 degrees and around 80% humidity) and starting to think I should have picked up the very slow instead.

I cut fluid back to 3 turns and 24 PSI. First two coats laid down very nice, but by the third the temp had crept up and I think it kicked quicker (I had fully intended to be done painting an hour earlier). Still it's got less peel than the factory paint on the truck so I'll take it. I believe it'll clean up.

PXL_20250620_143740414.MP.jpg
 
You must log in or register to reply here.
Back
Top