Spray Paint Cracking?

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Poboy kartman

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You don't have to wait a week.

Well, that's not exactly true. Many times these modern formulated paints have critical recoat times....and usually, you can recoat in under an hour, however, miss that window, and some require as much as 10 days wait.

But, why are we even talking about this????? Already pretty much covered earlier in this thread.
 

JMINDY

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I had this same issue a while back...


I'm fairly certain the issue is that Rustoleum takes longer to fully cure than what the instructions on the can recommended. I waited well past the time frame and still had the cracking when I applied the clear coat...

On re-coats of paint, there is a certain amount of flash time, which depends on the type of reducer in the paint and the temperature in the room, that you have to wait between coats to allow the solvent in the paint to evaporate. Too soon, and the solvent can react to the second coat ruining the first. Too late, and you need to lightly scuff the paint for the second coat to properly adhere to the first coat. I was told to always let the first coat flash a little longer than the directions (lightly tacky), then flash the other coats as recommended. This is because the first coat is what is adhering to the surface.

With spraying clear coating, you want it fully cured. Usually you want to wet sand and buff out any imperfections in the paint before clear coating. I didn't because it was just a gas tank. It was fully dried to touch so I assumed it was cured. My friends who are painters told me if I had tried to wet sand first I would most likely notice it getting tacky or gumming up my sand paper, thus not fully cured. They recommend always to at least find a hidden spot that won't be noticeable and wet sand it first to test before clearing. If you can lightly sand it past top coat without surface changing textures, it's fully cured.

Whether you have to wait 24 hours or a week for it to fully cure depends on a lot of factors...humidity, temp, reducer, paint product, etc.

Just what I've been taught, hope any of that helps...
 

crazykart

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As I stated for what I use: rustoleum, min wax oil based poly, and xylene. In even mild Temps you can easily spray base, then coat in clear in an hour without problems.

Even when I did miss the hour record window on one car because of work, in mild fall temps, I was coating (rather thick at that) in clear within 48 hours without any problems.

Yes solvents can react, if they are different. Yes paints cab react, if they are different. When you use the same types of paints, same bases, same solvents then the chances of reaction are slim to none.

That's why I also don't like using rattle cans. Even within the same brand different combos (base vs clear) can use different solvents. I would rather control every aspect myself. Buy the pint/quart/gallon can and the solvent I want (xylene or acetone depending on my time frame, and the flash times I want) and mix it all myself
When you control all aspects, and understand base structures as well as solvent flash times/reactions you are much better off.

I can honestly say though that I have never seen anyone ever have to wait a week between base and clear as long as they watch their times, and what they are doing. Now yes, miss your window, and you may just have to wait forever and a day, but then that's you own fault lol.
 

Poboy kartman

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Ok....Have I ignored the recoat times and I gotten away with it???? Yes. Have I waited very close to the prescribed week and had problems? Yes. With not only the same brand, but the base coat, not clearing over, but just applying another coat.

Now, being an ex-professional spray painter, I can appreciate the control afforded by mixing your own paint / thinner combination. However, not everyone has that luxury and without any specific information, it's basically chest thumping drivel that has nothing to do with this thread, which was about a rattle can problem.

BTW: The paticular paint I had a problem with was Dupli-Color engine enamel.....Can't find that in a can, and polyurethane isn't really formulated for high temperatures is it?

So, while some of what you have posted is useful information, some is not....bottom line....read the can...follow the directions....they are there for a reason.
 

crazykart

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Poboy, my response was to this:

Sand, Prime, Paint, then the big one Wait 1 week before you Clear Coat!

If you (as in the person painting) have to wait a week, then it's your own fault. Waiting a week is not necessary, and I have never seen a paint or clear that had an initial recoat window of 1 week. 48 hours was the most.

I was also saying that you have to know your base products, and solvents used, as they can change in even the same brands across different products, so pay attention.

Now while I may dispise rattle cans for many reasons, they are a necessary evil. All I was saying is that if you can mix your own then do so, if not then watch what your using, and make sure things match.

No you can't find duplicolor engine enamel in bigger cans (they should sell it) but you can find engine enamel in bigger cans for good prices.

But anyways, there was no chest thumping to be done there.
 

Poboy kartman

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True....however, I do prefer to wet sand the color coat, but that is a personal preference and certainly not necessary if you omit and recoat in under an hour.....and DupliColor engine enamel requires at least a week after one hour....(it's on the label in plain English) ........(and Spanish.....but don't get me started on that!)

EDIT: BTW: I have to say, after thinking about it for just a little while, I think using floor polyurethane is a terrible idea, and I'll bet none of those paint jobs are over 2 years old (and that's about their max lifespan) .
 

crazykart

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My T/A's paint job is 7 years old, will be 8 years in oct. Still looks great, gets a good polishing every spring, and thats about it.

The black camaro I posted earlier is 3 years, 4 in april, and looks as good as the first day I sprayed it.

As far as the other cars I've painted idk because theyve either been sold to people I'm nit close to, or I painted them for profit.

Idk why you would think its a terrible idea.
 

Poboy kartman

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I'd have never guessed it. I'm not sure that would fly here in Texas. MinWax polyurethane for floors is an indoor product and has no UV inhibitors....I'm afraid the Texas sun would make short work of it.....maybe the wax is protecting it?
 

crazykart

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Always, always wax. Rven factory paint and clear the sun will make short work of. Always wax, and use a good wax, not cheap crap. If you get the good stuff, and do it right then it only really needs it once or twice a year.
 

DaveP

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AS a auto body repair guy, for 20+ years,,,, what I see,, is called "Lifting" If you put a lacquer based paint on an enamel primer,,,, this is the reaction you get.

The Lacquer is WAY stronger of a solvent, then the enamel reducers.

EVERY coat you put on weather primer, paint, or clear coats The solvents actually go from the sprayed coat, all the way to the metal,, and then back out the layers,, and evaporates as it dry's. While painting a car in a booth,,, you have the opportunity to have not only the air flow,,, but a bake cycle, that speeds along the solvent evaporation process. after a good 30 mins or so,,, you can then go in and apply more color coats,, or the clear coat. But all of the primers,paints, Clears,, have the same base solvents, and are the same brands.

Thus mixing brands of base, color clear, is asking for troubles.

IMO the sand blasting, then powder coating would be the better way to go.
 

Poboy kartman

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That's only what you think you see...these modern day enamels are formulated to act more like lacquers nowadays than the oil based enamels of old....

Trust me...it's because of the critical recoat times some of these paints have that caused the problem....been there, done that....The results indeed mirror aplying lacquer over enamel ....but as I stated earlier, I've had this happen with literally the same rattle can of paint....and if you read the thread, the OP used compatible products and simply applied in that forbidden window.
 

DaveP

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yeah,, I guess, if your not there seeing what/how it's done,,, it can be deceiving. I've not had this problem with rattle cans,,, when the proper, cleaning, drying, degreasing, and applications are followed. <<< But that being said,,, Sh!t does happen. GOod luck to the OP
 
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OzFab

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If you (as in the person painting) have to wait a week, then it's your own fault. Waiting a week is not necessary, and I have never seen a paint or clear that had an initial recoat window of 1 week. 48 hours was the most.

:iagree: However, that's up to the individual & doesn't affect the overall finish of the paint itself...

Waiting longer means the colour coat has the best chance of "gassing out*" to avoid imperfections in the finish but, 48 hours is usually enough in optimum conditions! Obviously, in colder conditions, gassing out will take longer as the process requires heat...

If you recall (or not) I waited 6 weeks between the colour & clear on my kart; the main reason being bad weather but, the time was extended due to injury; the only downside to waiting so long is the colour needs to be wet rubbed to remove any possible contaminants before applying the clear...

*the process where the thinner evaporates from the paint, leaving a hard surface; if this is not allowed to happen, it may cause micro bubbles (aka humidity bubbles) in the clear coat...
 
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