View Full Version : How I mess up a paint job
01-25-2009, 07:07 AM
I asked questions here on painting my El Camino,got good advise.I've painted a few cars in the last 10 years and they looked good enough.
So I get the car all prepped,shoot on the 2k promer.sand it down,clean the car several times and clean up the garage.Got the heat cranked up to 70 degrees,all ready to go.
I decided on a black single stage urethane with a some flattner added.Not as flat as primer but semi gloss.Got paint , activator and reducer.The paint supplier says 4 parts paint,one part activator and one part reducer,apply two wet coats so it dries to an even semi gloss.A no brainer,I got my measuring cups and I 've done this before,right?
I spray the car one wet coat and it looks good with no runs or thin areas just a nice wet paint coat.Wait 15 minutes for the paint to flash while I mix more.Spray on the second coat with the same results as the first,leave the garage while the paint sets up.
I go back out after an hour to inspect my fine job.What the fuck!!! there's a color variation,some areas look flatter than others,something happened.
I check the paint paint and additives........Opps! Lots of activator but little reducer left.SHIT! Instead of 4 parts paint,one part activator and one part reducer, I mixed the reducer twice with no activator on the second coat!!!! Some much for paying attention to the labels.
Anyways,the paint still dried hard but has some glossier and duller areas.The car sides aren't too noticable but the roof and hood look like crap.I got paint left so I masked off the car again,sanded the new paint,and tomorrow I'll spray the hood and roof.
A lesson learned.
01-25-2009, 07:42 AM
You'll need to DA ALL that off and start over, as uncatalized basecoat will almost assuredly lift (wrinkle up like laquer over enamel) and you'll waste not only your original finish, but what you're applying. Plus, do you really want your finish over an unstable, improperly applied base?
01-25-2009, 07:57 AM
I ran into what Brian says. I fixed some spots on a car and where I went over uncatalized paint with catalized paint, the uncatalized paint lifted. The paint edge was feathered and the layer of the uncatalized paint is where the problem was. The paint guy told me that it is less likely to happen on older paint, my fix was less that 1 month after painting, and to also shoot the fix drier.
01-25-2009, 12:32 PM
I too would be worried about that uncatalized paint that's already on the car. At least just shoot a small area and let it cure a while, no use respraying the whole car and having it all lift up, that'll be even more work in the end.
Sanding off paint that lifted seems like you have to go all the way down past the fill primer to block it out. On a whole car you'd damn near have to strip the whole thing. I'd be cautious because it wouldn't be near as much work to sand it off the way it sits.
01-25-2009, 12:37 PM
Damn that sucks...I've done it too...gotta read the damn lables better I guess!
01-25-2009, 01:10 PM
Nothing will humble a person like paint. I feel your pain!
01-25-2009, 01:11 PM
Listen to what these guys are saying, if you paint over the non catalized paint, IT WILL LIFT. It will wrinkle up and be a total mess. Try to just wet sand what youve got with 1000 grit first, just to see if it will give a finish you can live with. I would try that before I stripped all that paint off.
01-25-2009, 02:12 PM
You are going to have yo sand it back down and get all of the uncatalized paint off before you can recoat it...yes it sucks but look at what you learned ...........
01-25-2009, 02:25 PM
This is why I hand the bodywork off to my brother!
That sucks, have fun with that DA!
01-25-2009, 03:33 PM
Well, I sanded the hood,not down to the primer everywhere but took off a lot of the 4 day old paint.I resprayed,and yes I mixed the ingredients in the right way :D I also really mixed the base paint very well. The paint didn't lift or wrinkle but it still looks like shit after several hours.And it is pretty dry right now.I am decent with a spray gun too.The supposed semi gloss varies from shiney to flat despite two wet coats that looked very even from any angle when wet.Again,the paint looks even with no runny or thin dusty sections.No moisture in the compressor and the shop temperature was 70 degrees before,during and after spraying.
I'm thinking there's a possibily with the paint,the flattner added by the manufacturer isn't equally distributed in the paint or drops out of suspension in the gun.I'll call the paint supplier tomorrow to see what they say.
I'm using an Astro gravity feed that's worked great for me on the last paint job.There's also a posibility the gun has an issue.Maybe unequal atomization that shows up more with this type paint.
At this point,fuck it.In a few days I'll sand with #400 to give a dull but even look and call it good to go for now.All isn't lost cause I got a good coat on the car to protect the metal. And it's better than a blown engine!!!
01-25-2009, 03:52 PM
Unlikely the problem is in the gun. What kind of humidity, if any was present while you painted and during the cure period?
Have you considered just sanding the finish with 1500 or 2000 to achieve a uniform semi gloss appearance? I've "dulled down" clear coat many times by juust color sanding in this way with good results.(good results meaning nobody could distinguish between the sanded surface and sprayed semi gloss)
It would at least give you time to enjoy the car some and let the paint completely cure out before you jump in again.
Hot Rod 47
01-25-2009, 04:24 PM
What paint products are you using??
I have seen many times with PPG that using their 2060 flat clear will give you a non uniform finish like you are talking about. But if you add in their SU4983 flattener it stays in suspension properly and the problem goes away.
01-25-2009, 04:33 PM
How well did you mix up the flattening agent before you mixed it into your topcoat? I've seen this happen when it isn't mixed well enough. I'm talking at least 10 mins on a shaker. The stuff clumps up in the bottom of the can and will stay there. When you think its mixed up good, stick the can to the bottom, if you don't feel the can all the way around the bottom its not mixed right. Even then mix it for another 3 mins. If you don't have a shaker, go to Home Depot and have them do it, they will. Used to al the time before I got a shaker. That would absolutely give you uneven gloss. Seeing as you say you're good with a gun, thats the only other possible reason. Unless the paint rep is retarded and sold you stuff that won't work together.
01-25-2009, 04:44 PM
did you seal the car before you painted it? if not, that,s probably where your uneveness came from. the car looked good "wet" but as it dried ,the primer absorbed the paint unevenly, especially where there was body work under the primer. uncatalysed paint will eventually dry, probably about a week to 10 days in the right conditions. it will make a good base, once it has dried completely and resanded with 500 grit paper. light coat first, then a medium to wet coat, and finally a nice wet finish coat should do the job! when you mix the paint, always add the hardner to the paint before the reducer, and this way you'll always at least have the hardner in the paint anyways!
01-26-2009, 05:23 AM
I doubt humidity is an issue.The garage is insulated with the gas heater running,temp at 70 degrees for a few days.Heated air is dry air.
The car was sprayed with 2K primer-sealer and block sanded before any finish paint work.
I bought the paint online from "Kustom Shop" in California.They put in the flat not me.I mixed the paint before use.Maybe they make a shitty product,who knows?
I did try to sand the finish with #1000 .Funny thing,the paint becomes glossy after sanding,the dull look is gone.It seems all the flat agent is at the surface and not distributed equally .But using #400 leaves a dull finish that I can live with for now.
bbc 1957 gasser
01-26-2009, 06:57 AM
plus you say its 70 ? the air or the car ..the car its self needs to be 70 or hotter ..
01-26-2009, 07:20 AM
You had mentioned a single stage with flattening agent.. its possible the flattening agent was not thuroughly shaken.. or it did not itomize with the color properly..,, Did you let it flash to the touch between coats.. thats important ... trapping unflashed paint will create problems. if you have a spare panel laying around try that method.. maybe try using the Flattening agent in clear.. and go over the spare panel to see how it works..
Do a test panel first to achieve what you want.. another hood spare would work..
01-26-2009, 09:03 AM
Looks like you forgot to seal the 2k and it absorbed at different rates. Off it comes and do it again.
01-26-2009, 09:20 AM
I've never used a flattener, but I've been told that what you're experiencing can happen. It may be that you're using a single stage paint, might the flattener work better in a bc/cc system where you are only flattening the clear?
01-26-2009, 09:43 AM
once the flattener is added to the paint, you will know if the two were compatible if it didn't curdle like sour milk, and i'm sure you stirred it good. as far as primer sealer, primer needs to be sanded, but as a sealer no sanding is required and should be top coated in a certain window, usually 15 - 30 minutes depending on the product instructions. also make sure all the products you are using are compatible with each other and not of different brands, this also makes a difference.
01-26-2009, 11:17 AM
There are several excellant suggestions for the failure you experienced mentioned on this thread. I mentioned humidity because, even though your both is warm and appears dry, if there is humidity in the outside air it can still effect your paint job. It seems most likely, however, that the problem is probably a combination of several of these things.
1. 2K primer should still be sealed prior to paint. It also has to completely gassed out prior to paint. Too thick a build can trap solvents just like in the top coat process.(ask me how I figgered this out!!). If you applied the primer thicker than the recommended procedure and faster then the recommended flash time, you could have this problem. Even though it sands OK.
2. The flatener HAS to be THOROUGHLY mixed prior to application and constantly agitated during the spray process. This may be the major cause of the problem. Flateners are pretty much universal and can mixed with about anything that doesn't specifically say ya can't, Just the same, I hate using flateners for just this reason, they are too hard to mix properly and consistently.
3. The catalyst could be a contributing factor but probably not the major cause of what you are seeing on the surface; the splotchyness seems to be coming from the bottom up. Improperly activated is a major problem, and is definitely contributing here, but might not be the main culprit.
4. The paint has to properly flash between coats. I usually let my first coat sit for 15 to 20 (or even 30)minutes depending on air temp and reducer. I spray the first coat the way I want the last coat to look... Wet to the point of being on the verge of sliding off.(if your first coat is full of orange peel, the last coat will have the same orange peel, only worse). I base the timing for the second coat on whether I can (not that I will) run a tack rag over the surface. I let each additional coat flash for at least 10-15 minutes, or till I can touch it without leaving a finger print (sometimes that's how long it takes to go around the car, so I might actually be just continuing the process stopping only to fill the gun.) I always mix all the paint I will need to finish the job before I begin. That way I just have to re-stir, fill the gun and keep going.
I leave the fan on with adequate air flow over the car for a couple of hours AT LEAST after I'm done spraying. Can't emphasize this too much. The paint has to gas out as much as possible before it starts to chemically cure. The chemical curing process takes several days, or even weeks to fully cure the paint. Reducers are still evaporating out of the paint during this process, even though you can touch, sand, etc on the surface. The more complete the chemical curing process, the more difficult it is for remaining solvents to escape. once the solvents are "trapped" and can't escape, your screwed.
6. The temp has to be consistant. the air, the car (and everything inside it), the floor, the walls, the paint and related materials, the gun. In warm weather this is not as critical as in cold weather (still important, though, just a little easier to control)
I don't know why your paint failed, but I suspect it is probably a little of all these facters that have been mentioned throughout this thread. sometimes it isn't just one thing that goes wrong. To complicate things further, it is possible to get bad paint. I've painted more than one job with material that didn't have any drier in it.......
I have another question, though... you say that sanding with 1,000 causes it to gloss up..... Is the paint balling up and clogging your sand paper????
01-26-2009, 11:38 AM
I'm thinking any of the things you guys suggest may have happened.If my shop was heated to 70 degrees before ,during and after work,I gotta say the car surface and the paint was 70 degrees.The 2K primer I used is listed as a primer-sealer,spray reduced for primer,no reducer for sealer it what it says on the can.If it really isn't,that would explain the look......... except I did sand down the hood and roof after the issue and spray again.I would think the previous sanded finish coat would seal the primer from the new coat of paint.All the other variables were taken care of,proper mixing,temperature, etc.Like I mentioned it appears the flatner is on the surface only and not into the whole layer of paint.That's why sanding with 1000 grit makes it shiney.
So I just got done color sanding with 600 paper wet.Then rubbed it out with very fine steel wool .Looks like an old bowling ball.Not exactly what I wanted but it's acceptable.
I think the bottom line may be that my skills are fine for shooting epoxy primer or typical shiney single stage or clear coat types paints.Spraying urethane with flattner may take a more experience painter than me to get it as it should be.I took some photos but the finish doesn't show up in the photo as it looks in person.
01-26-2009, 11:48 AM
Correction on the 2K primer...it say primer-surfacer on the can ,use a reducer if you want less primer build up.The can label says this product must be sanded prior to topcoating which I did.Must be fully cured before top coating,8 hours is best,I waited more like 12 hours.No where on the instructions does it mention using a sealer prior to topcoating.I'm assuming top coating means the coats of finish color.If not,then that's my bad judgement for not asking.
01-26-2009, 11:51 AM
Just another thought. How big of a batch did you mix up at a time? If they were small batches, say a quart at a time, the flatness of each batch can vary. As said before, the flattening additive settles out quickly and maybe the paint was not mixed consistantly with each batch, differing amount of flatening stuff in each batch. I have found that when I add the flatening stuff myself to the paint, it is tough to get each batch the same.
01-26-2009, 02:40 PM
I would be willing to bet its a humidity problem.
01-27-2009, 07:28 AM
I believe I figured out the problem.I was looking at a car paint internet site for the company that sells "Hot Rod Black".It's a urethane paint with flattner allready in it similar to what I used only a different company.
Reading the painting instructions for this different brand of paint ,They say 2 moderate wet coats.It also says a wet coat may produce uneven shades of flat and you may have to reduce the gun paint flow and or pull back the gun from the surface to get a dryer spray for an even satin finish.10 -15 minute flash time at 70 degrees .It goes on to say that spray gun handling technique is all important when using this paint.
The instructions on my paint said two heavy wet coats,15 minute flash time,no mention of special gun handling.A heavy wet coat to me says a wet surface all smooth and no dry spots,correct?
That's what I did along with 20-30 minute flash time at 70 degrees.I think this is too much paint and the gloss came out uneven.
When I first started painting ,I cut in the lower panels and around the seams first.I noticed a light coat left the paint a little fuzzy like regualar primer or too little paint.So I made heavier coats to get a smooth look with no orange peel.
Well, there's no orange peel or runs but an uneven gloss to the paint.
Maybe a more experienced painter coud have adjusted the amount of reducer to get a light coat with a smoother look.
I gotta say at this point in time that all the variables (temperatue,humdity etc.)were in order.I believe the main problem here is my spraying technique that is fine with gloosy paints or typical primer but not this shit.
Never the less, I painted the car to the best of my ability,it's done,the car has a good smooth coat of paint on it and I can live with the look.
01-27-2009, 08:07 AM
You hit the right answer. We are not robots. It's a learned skill and years of "muscle memory" to keep a spray gun at the exact distance for every coat. Even then almost impossible unless all you do all day is spray paint. You're also correct that with full gloss finishes it doesn't matter. Like you said, lessons learned. Flat clears are ok, but I'd think in your case one light dust coat to help with adhesion, then one even coat. Maybe do just the hood or decklid, or just leave it alone and get some miles on it.