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Old 03-30-2007, 07:12 AM
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Clearcoat problem....

I painted a car about 2 weeks ago, I waited 2 days and sanded with 1000 grit to remove some minor orange peel, then hit it with 1500, then buffed. It looked great the following day and the scratches came out easily but now after it sat for the two weeks I looked at it real close and it looks like there's some type of texture under the base or clear, almost like the base went on with some texture and the clear shrank and sucked into the texture. There are more noticeable scratches now also. I would say it's about a 6 inch paint job, where you have to be approx 6 inches away to see the defects. Is this normal or what can I do to prevent it?
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Old 03-30-2007, 11:21 AM
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This is called contraction and normally shows up in some reds, dark greens, dark blues and black bases as they are slower dry and the trapped solvents are now escaping so the base is contracting.

If the car has not been outside it needs a few days in the sun to get the rest of the tail solvents out then 1500 and buff again.
If the car has not been outside after a day or two the paint will become more textured as the rest of the solvents come out.

Correction is proper speed reducer for base (faster is not faster) and longer flash times between coats.
You can usually pinpoint where the solvent is the problem by the amount of time it takes to contract. If you applied the clear over the last coat of base to fast the contraction will show up next day or second day. the longer it it takes the deeper the solvent was and in a two week period that would indicate the second coat of base was applied to soon and problem is the first coat of base.

Last edited by BarryK; 03-30-2007 at 11:36 AM.
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Old 03-30-2007, 02:37 PM
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So do you recommend a medium reducer for the base or a slow reducer? Also, what would be the max time you would want to wait between coats of base?
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Old 03-30-2007, 09:44 PM
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Could his problem have been avoided if he had waited say 2 or 3 weeks before buffing the clear?
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Old 03-31-2007, 10:34 AM
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Flash time is relevant to the temp conditions your spraying at.
The tech sheet is a general guide but it does not take into account YOU.
If it's 90* and your using a slow reducer,it can be dry as soon as your done spraying the entire vehicle. But if it's 70* and a medium reducer,it could be an hour before it's really flashed off. It also depends on how heavy your coat is as well,the type paint your using,air flow thru the booth,just a butt load of things. Experience with the product is the only "almost" sure way to know but even then,S'IT happens. Bottom line with painting is this,Longer between coats is best. I know it's hard waiting but it's a necessary evil somedays.
When I spray Nason,it will take a good hour for it to flash off in moderate weather and this is even mixing reducers,Half fast,half medium. You want a slow enough reducer or catylist so it stays wet enough to flow out smooth. This is the difference IMO for a slick finish but it requires longer flash time. You use a fast reducer and it "skins" over and you "think" it's dry,but it's not and you hit it again and then you hammer on some clear and ***???
Paitence man,Paitence.
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Old 03-31-2007, 05:26 PM
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What's the longest time you would want to wait in between base coats before you have problems with the next one sticking.
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Old 03-31-2007, 07:54 PM
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If you're seeing scratches in the color then it's a prep problem. Curious, did you use a sealer and what kind and how long of a cure before shooting the base? It sounds like a combination of problems to me, but rushing the product mostly would be my guess... Metalic colors reflect surface texture problems-like scratches and orange peel, these often do not show untill the paint shrinks down during cure then they appear.
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Old 03-31-2007, 07:56 PM
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Depends on the brand but usually 24 hr. So an hour flash time between coats is no problem. Black is the worst. It takes a long time for it to flash so don't be in any hurry to recoat it.
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Old 04-01-2007, 04:49 PM
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I shot it with JP-375 (ShopLine epoxy) and waited right around and hour before applying any base. Why does black take longer to flash??
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Old 04-01-2007, 09:19 PM
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The pigment in the darker colors make it tougher for the solvent to evaporate out. An extreme example would be shooting black basecoat with fast low temp reducer, applying the coats too fast and heavy with little flash time, and not enough flash time before applying the clear-in this case the clear would dull out (dieback) and in extreme cases you'd see adhesion problems with peeling clear (delamination).

I think your problems can be traced to possible surface prep problems (missed sandscratches?) and an epoxy sealer that went on thicker than it should or it is having problems curing-possibly old hardener? Exceeded it's shelf life maybe? Sounds like a combination of problems. Epoxy is a slow drying product and if used as a sealer it needs to go on thin and smooth or shrinkage when it reaches full cure will sometimes show, on the higher end jobs it's best to seal and let set for a day in good temps then shoot your color-this gives it time to lock up good and shrink amd provides the best solvent barrier- 1 hour old epoxy doesn't offer any solvent resistance. Hope this makes sense.
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Old 04-02-2007, 11:48 AM
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Yes it does, how come it didn't tell me that on the tech sheet I'm usually just nervous thinking if I let the first coat cure to long I will have adhesion problems. I didn't know you could let the epoxy dry that long before applying base and that you could let base dry for an hour or two before applying the next coat of base. I'm still learning but I'm picking it all up
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Old 04-02-2007, 01:33 PM
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Another ringer here that could have caused a problem with the scratches showing up.
I'm not sure on flash or coating times of the Omni Epoxy but if primered to soon the solvents in the epoxy will play havoc with the 2K primer.
Sometimes the 2K primer will crack the next day because the epoxy solvents get into the 2K primer and it will affect curing of the 2K primer for sure, so that could also be another of a dozen things to cause the scratches to show on top of what was stated above.
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Old 04-03-2007, 05:20 AM
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How long would be typical of high build primers to cure? I think mine sat for 4 to 5 days before appying epoxy.
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Old 04-03-2007, 07:14 AM
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Quote:
Originally Posted by STATUTORY GRAPE
Yes it does, how come it didn't tell me that on the tech sheet I'm usually just nervous thinking if I let the first coat cure to long I will have adhesion problems. I didn't know you could let the epoxy dry that long before applying base and that you could let base dry for an hour or two before applying the next coat of base. I'm still learning but I'm picking it all up
Don't worry, i've been doing this for a while now and am still learning.. I think that is what keeps it interesting. And if it we're easy everybody would do it.
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Old 04-03-2007, 07:17 AM
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Quote:
Originally Posted by STATUTORY GRAPE
How long would be typical of high build primers to cure? I think mine sat for 4 to 5 days before appying epoxy.

If you waited 4-5 days you should be just fine, but with most primers you don't get full cure in 4-5 days.. It's definetely cured enough to top coat, but not fully cured.. This could take over a month depending on the primer you use..

If I have the opportunity I like to set them outside after priming,, that sure helps in pulling out the tails solvents. Same thing goes for clear coat for the following day.
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