The Latest Craze or "How My Paint Misbehaves"

[TheChronicOne]

OK, this is the type of thing that makes me pull my hair out and climb the walls.....


I prepped and cleaned thoroughly my styrene, then primed it, then let the primer fully cure for over a week. Nice. Right on track. Had a couple small specs of dust get stuck on the primer so I did a light sanding of all the pieces. Post sandning I cleaned everything with iso (I could have went and used water and dish soap but iso should work, right?)   I wiped and cleaned until the towel came back and white looking as it did before I wiped my pieces. Then, I let the pieces thoroughly dry.   Now, on to the actual paint....  a generic brand of white paint that I've used before with great success (go look at my American Militay Yak 9 thread where the white paint was one of the things that actually went off without a hitch and provide an excellent finish).

So, riddle me this... all things being equal and using identical methods and materials at the same time... why in the HELL do some parts craze while others turn out perfect?

Look at the wing tops over on the right.. is that not a great finish or what?! So, why did the other stuff I did the exact same way at the same exact time craze like crazy?!

Maddening... now I have to wait for it to fully dry then get to sanding....

Anyway, have a look:



What gives?!

EDIT: Working on providing a better picture.

[TheChronicOne]

Here, may be big but I want the detail to come out:

[Old Wombat]

Sorry, no answers but welcome to my world!

[TheChronicOne]

Sorry, no answers but welcome to my world!

Hahahah!!  Glad to be in good company, my friend.... 

It's a mystery, ain't it?!  It was weeeeeeird...

I could literally see the crazing happen as I sprayed.. it wasn't something that happened a couple minutes after I was done... as I sprayed, it crazed, severly,... all the while its neighbors 10cm away went flawlessly.     hahah! 

Usually I look at things like this as a learning experience and, "Hey, I learned that doing this provides this result...."  but this is like slicing a ham and midway through steaks start coming out.




EDIT: on the off or not so off chance that using isopropyl alcohol to clean was the culprit, I won't be doing that again. Back to filtered water and mild soap. As I said, I chose to use iso because I was lazy and didn't want to get up and go downstairs to whip up the water and soap. The iso was within arms reach. If anything, this may be a lesson in "don't be so lazy." 

[kerick]

Which parts did you spray first? If there were traces of contamination from cleaning the first spray of paint might have washed it out.

[TheChronicOne]

Which parts did you spray first? If there were traces of contamination from cleaning the first spray of paint might have washed it out.

I sprayed all parts pictured at the same time under the same conditions. That's what's strange, bro! 

Everything was done in the same fashion and at the same time. The same time I sprayed those parts that crazed I also sprayed the parts that look great. They were all cleaned, primed, cured, sanded, cleaned again, placed on the same sheet of clean newspaper, then sprayed in chorus. 

It would be like taking two basketballs.... bounce one with each hand at the same time.. one turns into a bowling ball instantly as you bounce them and the other remains a basketball.

[Dizzyfugu]

I'd also suspect that either the pigments did not mix well with the thinner, or that there was simply a chemical reaction between primer and final coat. What kind of primer did you use? From my experience, solvent-based primer plus solvent-based paint is a very hazardous combo (this is also true for varnish on top of that). I only had such accidents with solvent-based paint layers above each other, esp. when I used different manufacturers, even after thorough drying. Since then I try to use acrylic primer and acrylic varnish, and that is pretty safe.

[zenrat]

My feeling, looking at the horrorshow, is that it's incompatibility between paints.
The parts that didn't craze may not have done so because they got less paint.
How heavy are the coats you are spraying?
The recommended technique for enamels from rattle cans is;
Mist coat.
15 minutes
Mist coat.
15 minutes
wet coat.
15 minutes.
Wet coat if needed.

I'd rather have the problem appearing as I sprayed than after i've finished.
This looked great for a few weeks and then...

The problem was automotive lacquer clear over enamels.  The enamel continued to gas out under the clear cracking it.

[Dizzyfugu]

OMG... Had a similar case on one of the few cars I've built, a NASCAR Pontiac with Tabasco sponsorship. Thought that a white base with later red additions would be an easy ride, but I did not expect the mess that resulted from two solvent-based car paints from the rattle can sprayed upon each other... Looked similar, and I had to clean the whole car body in a brake fluid bath to save the project. 

[TheChronicOne]

I'd also suspect that either the pigments did not mix well with the thinner, or that there was simply a chemical reaction between primer and final coat. What kind of primer did you use? From my experience, solvent-based primer plus solvent-based paint is a very hazardous combo (this is also true for varnish on top of that). I only had such accidents with solvent-based paint layers above each other, esp. when I used different manufacturers, even after thorough drying. Since then I try to use acrylic primer and acrylic varnish, and that is pretty safe.

I used rustoleum 2X grey primer. It went down well and I let it cure for about 7-10 days. The white being Color Place paint (Wal Mart's store brand). They're both solvent based as far as I know. The white paint seems "thin" to me and you have to spray longer to get coverage... well.. I sorta "went to town" as I was painting and really layed it on thick.

[TheChronicOne]

My feeling, looking at the horrorshow, is that it's incompatibility between paints.
The parts that didn't craze may not have done so because they got less paint.
How heavy are the coats you are spraying?
The recommended technique for enamels from rattle cans is;
Mist coat.
15 minutes
Mist coat.
15 minutes
wet coat.
15 minutes.
Wet coat if needed.

I'd rather have the problem appearing as I sprayed than after i've finished.
This looked great for a few weeks and then...

The problem was automotive lacquer clear over enamels.  The enamel continued to gas out under the clear cracking it.

That's nutty right there! Yes, I agree, I'd MUCH rather notice the problem as it happens... that sucks, that looks like a sharp auto.  Charger? 

As I was telling Dizzy, I sort of went heavy handed and I think it's likely I tried putting too much paint on those parts at once...   The two little horizontal stabs and the underside were next to each other and since I glue the stabs onto sprue to use as a holder the way they were sitting in the table had them pointing up and down so I think I may have been trying to hit them extra heavy and... bam. In fact, now I remember at the time paint running down and pooling at the bottom before dripping off... soooo... yeeeeaaah...   Of course, it sure -felt- like I was painting it all the same and the wing tops look great!

Next time.. Instead of trying to spackle on all my coats at once I'll do the mist wait mist wet stuff you mention.

Horror show!! lol!! Yes, that's what I was thinking...

[kerick]

Yeah too much paint at a time never works out well.
That was the root of my problem painting my 50s movie space ship

[TheChronicOne]

Yeah too much paint at a time never works out well.
That was the root of my problem painting my 50s movie space ship

Thanks. Confirmation is good, means I'm on the right track. Sorry bout the ship but it sure is looking nice now! Eagerly awaiting next update on that one.   

In the meantime, I'm going to let all that crazed paint dry up probably one more day (one bad thing about this paint is that it stays tacky for days) then I'll sand it and go back to the "paint booth" and try again keeping in mind everything I've learned here. 

Thanks, y'all!!!   

[Librarian]

I have had crazing occasionally when spraying acrylic onto enamel. I've learnt my mistake and either avoid doing so or mucho kabuki tape.

[TheChronicOne]

I have had crazing occasionally when spraying acrylic onto enamel. I've learnt my mistake and either avoid doing so or mucho kabuki tape.

I tried brushing acrylic over sprayed enamel and had less than stellar results, myself.... when I'd go to peel my masking tape off, parts of the acrylic would come, too.     always learning!