Cleaning Up Automotive Urethane

[Didymus]

I've started using 1-stage automotive urethane paint for body color, and love it. You can choose from thousands of colors and you get a very bright, hard, even finish. (Gotta wear a paint-type respirator, though, with plenty of ventilation. Breathing urethane will make you sick.) But cleanup is a problem. The paint dries FAST on my airbrush, and once that happens, the UR-40 reducer seems to have little effect on it. Plus, UR-40 smells very strong; swishing stuff around in it is not fun.

SO: does anyone know a better way to clean up my airbrush after using automotive urethane? I've tried CSC; it works eventually, but not nearly as fast as it does with water-based acrylics. (Well, of course.) I've heard about using brake fluid, but it seems like weird stuff just to clean an airbrush.

Any other suggestions?

Didy

[slownlow32tl]

I use acetone also known as propanone, dimethyl ketone. But it is def not good to breath or get on your skin, so be careful. If i remember correct automotive paints are based on non-polar compounds which acetone will disolve.

[klutz_100]

Originally Posted by slownlow32tl

non-polar compounds

Does anyone else around here TOTALLY not understand paints and thinners? What works with what and why?!?!
WTF is a cellulose paint and why is it different from a lacquer?
Why are some auto paints water based and other lacquer based?
How am I supposed to tell the difference? What IS the difference?
etc etc etc....

I feel such a booby

Is there a definitive guide to paints etc somewhere?

:moan mode off:

[MPWR]

Well, let's see....

Polar implies ionic compounds, whereas nonpolar are covalent . Acetone is an organic solvent, and as organic compounds tend to form covalent bonds with carbon, so....

Does that not make polar solvents acids and/or bases? Damn if I can remember.

Ah smeg, it's been much too long since university chemistry. My understanding is that laquers, enamels, urethates and such are carriers for pigments. Acrylic confusingly can be either a pigment (acrylic laquer and acrylic enamel), and a polymer based carrier (Tamiya acrylic).

It would be rather helpful if someone who knows their poisons could straighten us out a bit.

[slownlow32tl]

I just remember from when i made steering wheels at rau-autowood.com, we used acetone to clean all our airguns. It pretty much disolves anything. But like i said it really bad for ya. My organic cehmistry teacher stressed that.

[Didymus]

Originally Posted by slownlow32tl

...automotive paints are based on non-polar compounds which acetone will disolve.

Because polar compounds only work in subzero weather? And they only come in white? And they only adhere to a bear... No, I'm gonna stop right here.

But seriously, folks, is there anything else that will clean up urethane paint that's been sitting in an airbrush for FIVE WHOLE MINUTES???

Even the official reducer - UR40 - doesn't affect it at that point. (But it sure looks purty on the car.)

Didy

[slownlow32tl]

Im tellin ya dude acetone. But if your soak your brush take out any rubber parts because it will eat them quick.

[white97ex]

I use lacquer thinner, the kind you can buy in a gallon can at wal mart. does the trick for me no problem

[Didymus]

Originally Posted by white97ex

I use lacquer thinner, the kind you can buy in a gallon can at wal mart. does the trick for me no problem

I'll try it the next time I use urethane. You're right, the smell is similar but not as potent.

Slownlow32tl makes a good point: There are plenty of "How I Do It" paint tutorials around, but I can't find anything that compares paint types/brands, tells what they REALLY are (labels are vague, they'll just say "acrylic" and leave it at that) and tells what can and can't be painted over what. I've even looked in the automotive literature - there must be 50 KINDS of automotive paint, some even water-based. Most of the information sources are brand specific; they don't get into mixing and matching brands or types of paint they don't carry.

I've just used water-base Tamiya acrylic Clear Coat over Dupont automotive urethane over automotive primer over resin and I'm hoping for the best, but I've never read anything that says whether or not the last two applications will cause problems. The guy at the auto paint place said "Well, that should be okay." Hmmm.

But it looks just fine after three days. And the color is amazingly vivid.

Didy

[white97ex]

as long as you use the harshest paints first you are ok. Don't use softer paints under harsher ones, that is where you get the problems. The solvents in the harsher paints eat up the softer paints like acrylics

[Didymus]

Just to close the loop: On July 3, I said I wasn't sure whether water-based Tamiya X-22 acrylic Clear Coat over Dupont automotive urethane over automotive primer over resin would be okay. Well, so far, so good. There's no evidence of any chemical reaction.

The Clear was mixed 1-1 with Tamiya thinner and airbrushed "wet," and no sanding was necessary. A light polish with Scratch-X produced a very satisfying deep shine.

Didymus