Need help w/ botched paint job

[strotter]

I'm painting my '72 with yellow PPG "MTV" paint, which is a one-stage catalyzed paint. I spent weeks prepping the car, bodywork and primering and dollying and whatnot, and got it pretty smooth. Well, not totally smooth but smooth enough. Anyway, I shot it last Friday morning in my semi-enclosed carport, first couple of coats looked just fine - picked out a bug here and there, one or two runs but no problem. However, as the day wore on it was getting warmer and I didn't really pay attention because I'm pretty used to it (central valley of California). By the time I got around to the third coat it was 11:00 or so and it was warm - in the low nineties, and the car was in direct sunlight. The third and final coat went on with a texture - it's like a really smooth orangepeel. Quite glossy, bonded on well, good coverage, but textured. Some areas are quite good, others are rough. I'd estimate that 1/2 the body area has got this texture to it. I spent the day today trying to see if I could sand it out, started with 1000 wet, went to 600 wet, and I just now experimented with 400 wet which cuts it flat in a reasonable amount of time. I haven't cut through anyplace, but I'm wondering how I should proceed. Probably I should just bite the bullet, sand it smooth, and put on a fourth coat, hmm? Or is it possible to salvage this mess? I'm not *really* sure what I did, though I suspect it was the heat, and I don't want to lay on another coat that will do the same thing. What do the old hands think?

[Guest Anonymous]

Step back and take a deep breath and get your head clear. Try to salvage the already applied color slowly and carefully. Sand,smooth and repaint. Thousands of brave home painters have been in your place before. You have color on there ...just get it even all over next time(s).Your paint is appparently hard and cured enough to take the abrasion of sandpaper. I have seen these little paint "planes" that remove runs and imperfections in paint . Try Eastwood catalog.Hang in there and learn (and watch that heat which caused the problem.. too much reducer/thinner when the atmosphere got hotter)Can sneak up on anyone xxxxxxx Racer X to the rescue you can take over now!

[Guest Anonymous]

Since this is sort of on topic, RacerX, what would cause orange peeling using a HVLP gun? My brother and I did some bike parts (back when he was messed up and shouldn't have been painting anyway... ) and it was his first time using a HVLP gun, he normally uses a small cup gun thats kinda small, like a detail paint gun (cup is below and about 2" around and maybe 6" tall), anyway, we read and were told the HVLP guns were the 'chit' these days and were supposed to cut back on overspray. It seems to lay down alot more paint than we were expecting. We got some runs, but more serious was the orange peeling. We were using SW 1 stage solid color (honda red) mixed per the instruction on ratios of paint, thinner and catalyst. Any pointers on use and adjusting a HVLP gun to reduce that sort of problem?

 

Thanks,

 

Don aka Lone

[strotter]

OK, I think I may have several problems here, but first I'll answer Racer's questions: I'm using an HVLP gun with the pressure at the gun regulator set to 25 psi, the compressor regulator set to 50 psi, there's a moisture separator on the line at the compressor. The paint is PPG "MTV" or "Omni TV" (depending on where you look on the can) in a green can, catalyst is PPG "Omni LV" (MH235, also in a green can), and the reducer is PPG MR 187 (purple can). The recommended mix ratio is 4:1:1, which I followed pretty closely. When I sprayed last Friday, it was really low humidity (maybe 25%). Temperature started at about 75 degrees at eight o'clock for the first coat, was about 85 at 9:30 for the second coat, and in the low nineties at 11:00 for the third coat, the one that curdled. I mixed separate batches for each coat.

 

I've been looking around on the web, and I think I've identified a couple of things I did wrong. First, I think I waited too long, given the temperature, between coats. The paint was quite dry to the touch between coats, beyond just "tacky". Secondly, per the above response, I didn't adjust the ratio of reducer to paint, so it was drying too fast. I don't know how much to add for a particular temperature - or do I get some other reducer altogether?

 

Another thing I think I did wrong is spray too little paint. There's a mark on the gun's nozzle that says "10psi Max", which I tried but it just wizzed out too little paint, with great big droplets. I didn't think that was right, so then I cranked it up to 25psi and I got a much better pattern with smaller droplets and more even pattern. Was that wrong? I adjusted the air feed almost wide open, then the paint. When sprayed on a vertical cardboard surface, it took maybe three or four seconds of constant spraying before runs began. The pattern was about 3" wide and 6" high when held about 10" from the surface. During each spray session I ended up turning up the paint feed just a bit, because my arm was getting tired.

 

I've been working to clear off the texture, but I've managed to cut through now in several places so I'll be applying at least one more coat. I'll be going by the paint shop tomorrow morning, and ask the guy about this then. (It occurred to me that I should bring a sample with me to show him - one of the headlight buckets should do just fine). Hopefully I'll get some clarification then.

[strotter]

I talked to the guy at the paint store, he agreed that I was waiting way too long between coats - he said "Finish up the first coat, go over and mix up the next batch, filter it into the gun, and start on the next, so on." He also said the paint *has* to be tacky, and this is where the heat affects it the most because it causes it to catalyze too fast (like Bondo on a hot day) and the new layer doesn't integrate and spread out into the previous layer - when you're done, there will be one continuous coating of paint. He also suggested that the time between coats is the time between when I *start* painting the first part, to when I *start* the second coat on that part again, not to when I finish the last part. Does that make sense? The paint on the first part doesn't care how long I take getting the hood just right, it's just drying away regardless.

 

Also, he suggested I not fiddle with different reducers and ratios - it's just too many variables for the beginner, it affects how the paint behaves when spraying, so on. Rather, he said, pick a time of day when the temperature is around 75 degrees, the temp for which everything is calibrated. Ten degrees either way is not a problem, so I should shoot the first coat real early when it's 70, and by the time I'm done it'll be 80 and the paint will be happy. On a practical note, earlier hours equals less sanding out of bug feet (they leave a little black dot. It's sad, but also a little funny). Also, the temperature of the *paint* is what matters, nothing else. So, keep the paint cans out of the sun, don't let sunlight fall directly on the car when painting (though this won't be a problem with the yellow I'm shooting). Overall, he said that if you think of catalyzed paint as epoxy (something I'm pretty familiar with), rather than the stuff you get in cans, you'll be doing OK.

 

Finally, he said "Don't expect every area you paint to behave the same. The way you did the hood might not work on the fender. Watch what you've just sprayed, stop and study it if you need to, and adjust your spraying style to get it right." Consistency, he suggested, is the key for beginners. Properly done, it should require no sanding or smoothing, should be a consistent color, and have no texture at all - smooth as a mirror. Because I'm spraying over the same color again, I won't have to worry too much about coverage, and can concentrate on surface.

 

I forgot to ask him about setting up the gun but for now I think I may have a handle on what's going on. I just keep telling myself "It's not a pain in the butt, it's a learning experience." Oh well, I've had *much* more expensive learning experiences, this one isn't too bad.

[Owen]

Sounds like the counter guy gave you good advice. You mentioned o-peel, my first job was so bad it looked more like pineapple peel! The first time, I was too worried about runs and had the gun too far away. The second time, with the same gun settings, I moved the gun in closer and came out with much much better results. Remember to move the gun faster when you're in closer.

 

You also mentioned cranking up the PSI, as well as spray coming out in droplets. Where are you measuring pressure? It's not the same as the gun INLET as the gun TIP. Depending on which gun you have, I was told to measure PSI at the tip (with a gauge at the gun inlet which measures this) when the trigger is all the way open.

 

I also have not heard of the MTV paintline, is your gun the right tip size etc for it?

 

Good luck! I just recleared my car this weekend and its much better, even with all the dirt and stuff. Can't wait to color sand it.

 

Owen

[strotter]

Well, I just shot 3 more coats. I took a different approach this time - all I cared about was "smooth". I was *considerably* more aggressive with the applications, laying on more paint, turning up the paint volume, going back as necessary when I spotted a problem. Yes, I created quite a few runs, but I know how to handle runs after it's dry. The overall result? Smooth as a baby's butt. I started early, moved quickly, and layed on the coats bang bang bang, as quick as I could mix a new batch. Like I said, there's some overspray and runs, but that's *handleable*.

 

An interesting aside. After reading your mention of the three minute flash time, I performed an experiment: I laid out the "small pieces", such as the louver/vent panel (the piece behind the hood that hides the wiper motor - what's that called?), the valence, so on. They had been stripped bare and primered, sanded smooth with 220 wet. I prepared a "half-load" for them, and painted them one coat at a time then immediately went back and recoated them, taking about five minutes between coats. The result? Gorgeous. Perfectly smooth, no overspray (though they were sitting within inches of each other), no orangepeel, great coverage, perfect. Each coat just sort of melted into the previous one. At one point I spotted a bit of overspray and watched it melt into the previous coat. Interesting, eh? I think that if I need to do a project like this again, with the car disassembled, I'll prepare a load of paint for each part separately (such as left fender, right fender, hood, so on) and concentrate on them one at a time.

 

Something else I learned: lighting is *important*. I used the rays of the sun to eyeball the paint after I finished each pass - I must have looked like an idiot, bouncing my head up and down, trying to put the sun's reflection in just the right place. If I spotted an under-coated area, I'd hose it down as necessary. Previously, I followed the "each pass should overlap the previous pass by half its' width" rule, but with my lack of skill that would frequently leave some areas more painted than others. You have to *see* what you've just put down, one way or another. Hmm. Something I really hadn't thought of, but I suppose is really obvious (especially in hindsight).

 

This has been interesting. I'm sure I'll be cussing like a sailor Sunday when I start sanding out the runs, and there are areas I'll have to mask and repaint, but for right now it feels like a victory. Go me!

[Owen]

"I used the rays of the sun to eyeball the paint after I finished each pass - I must have looked like an idiot, bouncing my head up and down, trying to put the sun's reflection in just the right place."

 

This is a great thing to do and you're right for doing it. It's always best to check the surface at many angles, I prefer a fluorescent light myself.

 

As for your runs, try a run blocker, which is basically a file used to cut the runs down flat.

I bought mine from a paint supply store but I've seen them in JC Whitney recently.

 

Owen

[Tim240z]

I must have looked like an idiot, bouncing my head up and down

Ha Ha ...no comment!