Clearcoat bubbling paint...

[gbkd80]

Well, I just had a "finish catastrophe" lol. 

Decided to finish the enclosure on an AC128 Fuzz Face replica I built a few weeks ago.  It's not my first time painting an enclosure, but it's technically my first time applying a clear coat to it.

So, this is what I had originally:


1590BB, sanded with 60, 120, 400 and 800 and cleaned with acetone.  Painted with Rustoleum 2x paint/primer.  Did not apply a separate primer coat (wondering if this was my malfunction).  Did several coats and let it dry.  Now, one of the instructions on the can, which I never read but happened to this time, said to clear-coat within like an hour of drying or something like that, or wait 48 hours.  I'm guessing that the "wait" period is because of the solvents in the paint as it cures may react with the clear coat.. I dunno.  I'm pretty sure it's been 48 hours since I finished that box.  I then applied the waterslide decal (that is another issue, but considering it came out of the water like crumpled cling wrap I'm amazed it even smoothed out where it is). 

Bought 2 different clear sprays and already had a DuPont Acrylic Clear from the local paint store when I was repainting a part on my car.  I bought Tree House Studio Clear Acrylic from Hobby Lobby, and Rustoleum Crystal Clear Enamel.  I grapped an old painted piece of metal and sprayed the Hobby Lobby stuff on it; it bubbled up.  Wtf?  So I then took the bottom painted plate of my pedal and tried the Rustoleum... same thing...?  So Now I'm just frustrated thinking, it must be my prep... I didn't sand the bottom cover.. but I did sand the living jesus out of the enclosure.  So I grab the known-good-problem-free DuPont clear and spray the pedal.  Looks good so far.  No issue and then about 5 minutes in:



Ruined.  I went to scrape it off knowing it was over and the paint literally just slid off the pedal.  So what gives?  Did I really blow this up by not using a primer coat first?  I can't imagine it's any one of the clears that I used causing the issue since they all did it.  I'm more interested in sticking with the DuPont because it's basically automotive clearcoat but I need some tips on what I'm doing wrong so I don't do this again and waste days...

[peterg]

Could be a number of things:

-dirty acetone will cause the paint not to adhere. I usually just wash the enclosure with hot water before painting.
-incompatible paint and clear coat - using Rustoleum paint and clear coat should have helped.
-too many coats of paint and/or improper drying time between. Have you tried baking the enclosure in a toaster oven before applying the water slide and clearcoat?
-too thick of a coat of clearcoat

[Cozybuilder]

Bummer. I clear coat with lacquer- the first coat is a light dusting, then in the hot box for ½ hr, another misting, hot box, 400 grit or finer light- no pressure, mainly getting rid of dust, wipe off with denatured alcohol, a light coat this time, more than before, back in the hot box- now you should have enough of a protective barrier coat that will allow you to spray heavier coats, with flattening between. The solvents in lacquer dry fast, but are potent- thus the dust coats first.

[gbkd80]

Great advise from both... thank you. 

No, I did not bake the finish.  I just learned about that in the last week or so, actually.  Sounds like a good idea to ensure it's dry and adhered well..

I did try the rustoleum clear on the bottom plate which was coated the same as the rest of the box and it still bubbled... that's when I started thinking my prep was just not good on the bottom.

This time around I did wash it in the sink with hot water and dish soap assuming that oils or contaminants were present.  I'll try those suggestions this time around.  Thanks again.

[Cozybuilder]

Rustoleum primer first!! It makes a noticeable difference in the paint adhering well.

[bluebunny]

Yep, use primer.  And make your coats thin.  This is my regime:

• prepare enclosure (I'm usually pretty lazy with this bit!)
• primer coat
• wait 15/20 minutes
• primer coat (if needed)
• wait two days
• paint coat
• wait 15/20 minutes
• paint coat
• wait two days
• decal
• wait 24 hours
• clear coat
• wait 15/20 minutes
• clear coat (sometimes a third or fourth clear coat...)
• wait one or two days
• wiring!

[bloxstompboxes]

I agree on thin coats. It looks like you tried to get all the clear on in one coat. That pic where the paint has wrinkled should not be so shiny like that. The clear should be put on very thin at first and then a little more liberally which each coat after that. 2 or 3 coats is what I usually do.

[gbkd80]

Thanks guys, I'm going to follow those steps.  I already sanded down the enclosure and am back to a clean starting point.  Will go out today and get some primer.  I was a bit leery when I bought the 2x (primer/paint) combo stuff because I don't really believe that actually works the same as a separate primer coat but, eh.  I learned my lesson.  Oh, and the DuPont clear seems to lay down thicker than the other stuff but you're right, I did give it a good blast at that point of frustration.   

[R.G.]

Chemistry.

Enamel(ish) things are solvent or semi-solvent drying oil-derived coatings with pigments in them. Lacquers are resins suspended in a solvent solution. Lacquer solvent is quite aggressive, including attacking cured/dried enamels. You can use this effect if you like. I experimented with lacquer over enamel directly to generated crackle finishes, and the "crackle" finish stuff in home stores uses a variant.

The real answer is to never use lacquer over enamel if you don't want to damage the enamel. Use a different chemistry. Enamel goes with clearcoats other than lacquer based. Lacquer clearcoats go over not-enamel.

Not-enamel includes lacquer (doh!), epoxy, urethanes, etc.

Catalyzed urethanes are in general the toughest, strongest, shiniest, etc. coatings, but suffer from being really difficult to use and toxic when not cured.

Paint chemistry is very, very complex. The old saw exhorting the user to read and follow directions is especially pertinent, as well as "test on an inconspicuous area". The best version of testing on an inconspicuous area is to try your proposed paint stackup on a piece of scrap before trying it on your lovingly built pedal.

[Cozybuilder]

What RG posted is true.

However if you want to use lacquer over enamel for various reasons*, the way I outlined above will allow it, and you'll wind up with a quality non-bubbling finish. Really thin, mists really, for the first couple of coats is key, and allow to fully dry between all coats (I use a 60W incandescent bulb for heat in an old stove, T is just right, drying racks built in). I've had problems with acrylics not fully drying, and don't mix urethanes (already survived cancer, don't want to try again).

*great look, dries quick, levels well, its tough

[bluebunny]

I should add that my paint and clear-coat products both come from a UK auto supplies shop: they're designed to go together.

[R.G.]

The mist coating process lets droplets of lacquer eat into small locations in the enamel and dry. Future mist coats eat their own locations until you finally get a full coating. This works because the surface to volume ratio for tiny mist drops is way different from the normal droplets in normal spraying.  The solvent is confined to one point on the enamel and it dries before loosening the enamel under it.

Or, for short, square-cube law.   

I should add that my paint and clear-coat products both come from a UK auto supplies shop: they're designed to go together.

... and this is the right way for us non-chemists/painters.

[R.G.]

The mist coating process lets droplets of lacquer eat into small locations in the enamel and dry. Future mist coats eat their own locations until you finally get a full coating. This works because the surface to volume ratio for tiny mist drops is way different from the normal droplets in normal spraying.  The solvent is confined to one point on the enamel and it dries before loosening the enamel under it.

Or, for short, square-cube law.   

I should add that my paint and clear-coat products both come from a UK auto supplies shop: they're designed to go together.

... and this is the right way for us non-chemists/painters.

[karbomusic]

I experimented with lacquer over enamel directly to generated crackle finishes, and the "crackle" finish stuff in home stores uses a variant .......The real answer is to never use lacquer over enamel if you don't want to damage the enamel

What RG said. I use it on purpose from time to time; you just have to be aware of your paint types:

[R.G.]

I think the original crackle-painting pictures are still there on geofex... hmmm... yeah. Here: http://www.geofex.com/Article_Folders/craklpnt.htm

I spent some time getting this:

[stringsthings]

I've got a similar approach as bluebunny.  I've been using Rustoleum spray cans and have not had a problem so far:


    prepare enclosure ( 100 grit, then 220 grit, clean with alcohol )

    thin primer coat ( Rustoleum self-etching primer )
    wait 5 minutes
    repeat for 2 more coats
    wait one-two days

    thin paint coat
    wait 10 minutes
    repeat for 2-3 more coats
    wait two days

    decal
    wait 24 hours

    clear coat
    wait 10 minutes
    repeat for 2-3 more coats
    wait at least 2 days

    wiring!

I've used regular Rustoleum and the 2x paint/primer kind with no problems.  Thin coats help keep paint runs down.  The drying time between coats is pretty short,
but I always let it cure thoroughly after the last coats ( of color or clear ).

[Cozybuilder]

I think the original crackle-painting pictures are still there on geofex... hmmm... yeah. Here: http://www.geofex.com/Article_Folders/craklpnt.htm

I spent some time getting this:

Thats a great crackle-paint job- absolutely love it!! Might have to try something along these lines for my next planned build- its in a 1590B wedgie, and needs a little something extra. Pink crackle?

[gbkd80]

I think I got things sorted out now, following the instructions and waiting patiently to finish it, I'm satisfied with my results.





I sanded the box back down with 60-grit paint removal sandpaper, then smoothed it up a bit using 400-grit.  Spent a good amount of time doing this.  Then I used Rustoleum etch primer, 2 coats.  Did a couple coats of Krylon Jade satin (happened to have a new can of it from an un-related project), and finished with the Rustoleum Crystal Clear enamel. 




Thanks everyone for the help.  Really happy with the way this one came out. 

[bloxstompboxes]

Looks really good. Excellent job!

[stringsthings]

I sanded the box back down with 60-grit paint removal sandpaper, then smoothed it up a bit using 400-grit.  Spent a good amount of time doing this.  Then I used Rustoleum etch primer, 2 coats.  Did a couple coats of Krylon Jade satin (happened to have a new can of it from an un-related project), and finished with the Rustoleum Crystal Clear enamel. 

Excellent job  The knobs work very well with the paint color.

That's exactly the same primer and clearcoat that I use.