Thursday, October 25, 2007

Idiot + Spray gun + Toxic chemicals = ????

It didn't take me long to find a use for one of my new air tools. Of course it's the one I have ZERO experience with - the Devilbiss JGA spray gun. Turns out this thing is quite popular in the automotive refinishing world. Pretty much the one every painter has in his kit. It's not the absolute pinnacle of technology, but it's reliable, and gets the job done.
Well, now I've got one too, and have no idea how it works - so I figured it out the same way I figure everything else out.

I took it apart.

Turns out it's just a big honkin' airbrush - I've used one of those before. This has a few more knobs to turn, and moves a lot more paint, but has the same basic functions.
So I've decided to use it to paint the interior of the Neon. Originally, I was going to just use a bunch of spray paint from Home Depot, but at $4/can x 24 cans (estimated 12 primer and 12 topcoat) that adds up to almost $100.00 fast. As it turns out, all the stuff to get set up with real automotive enamel, reducer, hardener and safety gear is about the same, but now I'm set up and future jobs will cost significantly less.

But wait - you can't just go blasting paint around the interior of a car can you? You've got to mask off everything you don't want painted, right? Yes, unfortunately you do.
Masking off the inside of a car is no small task, especially if you're a bit obsessive about things - which I most certainly am. You can't imagine how many little nooks and crannies there are inside the passenger compartment of a simple car like a Neon. I'll forgo the play-by-play and just say that it took me nearly a week of working a few hours each night to get ready to paint. Somehow, I also forgot to take pictures of the inside before paint. But here are a few of the outside:







In the 2nd & 3rd pictures you can see the main reason the masking took so long. The white plastic garbage bag sitting on top of the dash contains the entire interior wiring harness for the car. It starts at the driver's side of the dashboard, runs along the left side of the car, splits under the rear passenger seat, continues down both sides of the car, feeding power to all manner of door switches, fuel pumps, and rear window defrosters along the way. Finally terminating at the tail lights and license plate light. I chose to painstakingly (and non-destructively) pull the entire harness all the way forward, and tape it up in a bag so it wouldn't get painted gray. Why? Because I'm nuts I guess...I wrestled with the decision for several evenings before I finally gave in to my obsessive ways. I just couldn't bring myself to paint over it. It seemed so unprofessional and half assed. I just can't do things that way, and I like to think that the attention to detail and extra effort will be noticed when people peer into the car. Especially when I point it out to them.

So now the car is all masked off and I've got all the materials to do the job. But I've never used pro level automotive paint and let me tell you - it's like a freakin' chemistry class. You've gotta mix all this super toxic crap together, and then you've got the added stress of something called "pot life". As it turns out, once you mix the paint, you've set a chemical reaction in motion, and it cannot be reversed or slowed. The paint WILL cure and harden no matter what. That's known as "pot life". Once that paint is mixed, you've got to spray. If you can't spray, you've got to get it out of the gun in a timely manner otherwise your little chemistry experiment will turn to a solid plastic puck in the gun and ruin it. Soothing thoughts eh?

Undeterred, I set off into uncharted territory. Mixing up automotive paint. It sounds easy enough, but it involves measuring out magical amounts of outrageously toxic chemicals to achieve the perfect mixture that will dry to a nice, even coat. Not an operation for the timid...
Luckily the guys at the paint store gave me an idiot-proof formula to eliminate all the confusion. "You take a quart of paint, put a pint of reducer in it, and add 4 oz of hardener - you should be all set bro" Sounds easy enough.
Well bros, a quart of mixed paint is a LOT of paint - like enough to do one coat on an entire car. I realized this just as I was about to mix my first batch. Unfortunately, cutting the formula the shop gave me down to make smaller batches required more math than I cared for. In the end, I had to reverse engineer the formula the shop gave me - using the following logic:
1 quart equals 32 oz. Add 1 pint (16 oz) to that and you get 48 oz. I've been told to add 4 oz of hardener to that amount of paint. Therefore, whatever the ratio of hardener to paint is, will be true no matter how big or small the batch is. I hope.
Simple math tells me that 4 oz is roughly 8.3% of 48 oz.
Let me share something here - I was not a stellar student back in the day. Furthermore, I don't deal with liquid measures on a daily basis. The above operation required that a fairly large chunk of my gray matter be dedicated to the math involved. I could've used a nap afterward.
No matter - now I've got my percentage - all I have to do is mix up the paint.

Along with the unintentionally confusing formula, the shop gave me a bunch of disposable mixing cups with all these measuring lines all over them. While I was mixing up my first batch, I figured I'd use these lines to make sure I added a known amount of paint in order to make my math easier. Halfway through, I realized that around the cup's brim were graduations for a bunch of different formulas - none of them looking like anything I'd need - that is except for the very last one - 2:1+10%. Dammit, dammit, dammit!
Well, I took some consolation in the fact that I was only 1.7% off.

Using the measurements on the cup, I mixed, I sprayed, I succeeded.
Behold!

Looking rearward - The funny looking "wishbone" is the parking brake cables tied together, and strung to the roof to keep them out of my way.


Looking forward


The trunk


Not too shabby for a rookie eh? I'll do a full "Before and After" when I get it all put back together.

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