paint problem

[jonathansuhr]

I use krylon clear coat on all of my pedals, but today, i clear coated a pedal i painted white, and the paint started cracking and became liquid again, even though i cured and dried it. am i using the wrong white paint?

[Kearns892]

Was the pedal warm? Same thing happened to me today, and I'm pretty sure I got impatient and didn't let it cool after baking long enough. Sanded it down and started over. We'll see how it goes this time...

[BAARON]

Many white paints are extremely sensitive and reactivate easily.  Make your first coats of clear very thin and misty and make sure they aren't thick; this may help a bit.

What kind of paint are you using?  (Brand and composition?)

[jonathansuhr]

im not exactly sure. it's a no brand spray paint the just says "spray paint. interior/exterior. fast dry"

it says it contains toluene, acetone, and xylene.

[jonathansuhr]

it seems that those three chemicals are the same ones used in lacquer thinner. so maybe i did get the wrong type of paint?

would white lacquer work?

[BAARON]

Beats me, I've never used white lacquer.  Dano at Beavis Audio Research suggests Rustoleum spraypaint, though.  I imagine it's probably a safe choice.  Rustoleum has a lot of experience making paint.

I'd probably avoid any spray paint that does not state what kind of paint is inside the can, because that's an accident waiting to happen once you start covering it with other stuff.  People who manufacture those generic spray paints don't have top-coating and fine finishing in mind: they have lazy weekend carpenters and crafters in mind.

[Toney]

What you are describing pretty much sounds like the thinners from the clear coat re-liquifiing the earlier ones.

I have had it happen with auto paint when I have been impatient and applied too thick a coat too soon before the previous one has dried. Seems more relevent when you change types too eg from enamel to gloss coat.

Best solution, assuming the paints are truly compatible, is to be 100% on the base coat being dry, then hitting it with a light 'breeze' coat and allowing that to fully cure before spraying again.

 

[Toney]

Oh another point that I don't always see raised with pedals....

You MUST use etch primer if you want your paint to stay stuck to aluminium.
I only use auto paint. No-name 'touchup' enamel is asking for problems.

[m-theory]

It's called recoat lifting.  It happens when the product that you're spraying attacks and re-wets the substrate.  We're not spraying catalyzed products here, so everything that we spray can be re-wet. 

If you read the back of the can, it'll say something about recoat times.  Generally speaking, if you don't recoat within an hour, you have to wait up to 7 days...sometimes less...depends on the product.  At any rate, whenever you recoat a non-catalyzed substrate, regardless of how long you wait, you risk recoat lifting.  The solvents in the sprayed product are usually going to be aggressive enough to attack and lift the substrate, either if coats are pounded on too heavily or if you scratch the substrate (which you need to do with a fully dry substrate, in order to obtain proper adhesion with the additional coating). 

The BEST way around this is to let your primer dry well enough to sand on it, then do all of your finish coating within that recoat window given on the back of the can.  In other words, you let the primer dry for an hour or more, sand it, clean it, then apply multiple LIGHT coats of color, allow that to dry no more than an hour, then clear, if you're using spray bomb clear.  I hate that stuff myself...not only will it lift the hell out of what's underneath, but it sucks down and dries dull, and needs to be buffed furiously to produce a decent finish.  More often than not, you'll sand through when you're buffing it up.  After all that effort, it still scratches with a fingernail.  It's just a terrible product, imo. 

Rustoleum will still lift, just like any other non-catalyzed product, but it's probably not as likely, because it's an alkyd enamel base, and that stuff is pretty fool proof overall.  I hate it, because of the stupid long dry times, but I have to admit that, when it's dry, they make my favorite primer for this stuff.  I've never seen such impressive adhesion from a single part primer, on bare aluminum.  I've got a bang-around box that I recovered from a previous build to become my test platform box.  I stuff circuits in it to take on stage, and try out in a live setting.  When I gutted it initially, I applied a couple coats of Rustoleum primer onto the bare metal, after I sanded it, and even after over a year of being literally thrown around, there's not a hint of peeling anywhere, in spite of numerous road dings and chips.  You couldn't peel that stuff off with a knife.  As a former auto refinish products salesman, I'm impressed. 

In your recent case, you've gotta sand to bare metal and start over.  Btw, if you're baking this in a toaster oven, you're making it more susceptible to lifting, because the heat will form a rigid skin on the surface that will trap solvents underneath.  I've had lifting every time I've ever tried to bake, and finally figured out that it wasn't worth the hassle.  I started doing my entire finish process all within the recoat windows of the topcoat products, and have never had a problem since. 

[jefe]

See, this is why I tend to shy away from painting in general. A lot of effort for questionable results.

That said, I just came from the auto parts store with a few rattle-cans in tote.    Some Duplicolor self-etching primer, some gloss black, and some black wrinkle finish. I don't have very high hopes in my ability to make this stuff work without dripping & running, or peeling later on. But, the weather is finally getting warm enough that I can try a little spray painting outside on some cheap junction boxes. I won't feel too badly if they come out looking like crap. 

[m-theory]

See, this is why I tend to shy away from painting in general. A lot of effort for questionable results.

It's really not that difficult to achieve really good results.  You just have to have a bit of knowledge going in, and be willing to follow the proper steps carefully.  I can tell you without hesitation that the times I've had failures have always been when I've been trying to rush things along.  Sand the primer before it's dry and you get grooves and gum.  Spray coats too heavily or don't wait for coats to flash properly and you get runs.  Recoat beyond the safe recoat window and you get wrinkling/lifting.  Don't prep the metal properly or apply primer and you get peeling. 

Like anything else, it requires some practice and some patience, but as long as you abide by the basic guidelines, it's really not difficult to produce nice results.  That said, like anything else as well, some will do it, some won't.  That's why there's a market for pre-painted boxes. 

[jefe]

Yeah, I'm sure that some of my past spray painting errors were due to my impatience. And because of that, I've never been willing to go out of my way to gain more practice at it - which would obviously make me better. There are just so many areas to go wrong, even others that you don't mention... like environment. I can't paint indoors because of fumes and overspray, I can't paint outdoors for half the year because it's too cold... and even when conditions are perfect, I've done several hours of prep, reading all of the directions, things are going smoothly... and specs of dust get in there and completely ruin it. Honestly, some of you guys must have the patience of a saint.

The only reason I'm tinkering with paint right now is because I'm working with some steel boxes, and I don't want them to rust. Otherwise, if it's aluminum, I think "bare metal" is a nice color... lol...

[GibsonGM]

I use Krylon Crystal Clear for a clear coat, and use auto primers & paints (generally) for boxes.  I get good results by (as said above) allowing full drying time on the substrates (primers and finish paint).   Once it's all dry,  the 'mist coat' of Krylon, allowed to dry, does well at sealing what's below it and preventing re-wetting.  Have never had a problem.  Then another 3 coats of the clear tend to make a nice solid top coat to resist abuse (for the most part!). 
Light coats seem to be the secret to preventing runs and having good adhesion.  Just be patient and go slow.  After 2 boxes, you become a pro with spray paint, lol.