Enamel over lacquer?

[berr13]

Remind me, everybody--can enamel be sprayed over lacquer? I had two botched paint jobs yesterday, both using Testors Custom Lacquer System (those are the spray cans mixed to factory colors). In both cases the cans began spitting out blobs of paint, even though I'd warmed both in warm water and shaken both for several minutes. Now I think I'll go back to enamel, something I've always had better luck with. So I guess I have two questions--can enamel be put over lacquer, and what do you all do when the can goes crazy on you like mine did?

[chunkypeanutbutter]

I'm pretty sure enamel and lacquer would craze. As for the cans, try cleaning the nozzle from the bottom with a pin to unclog it, or rinse it out with mineral spirits.

[Snake45]

Enamels go over lacquers fine. An so far, I've had no problem spraying the Testor lacquers over airbrushed and/or THOROUGHLY DRY enamels.

I suspect your problem is a clogged nozzle. I've gotten in the habit of, at the end of a spray-bomb session, holding the can upside down and spraying about a one second burst to clear the nozzle and have had pretty good luck so far. Try switching nozzles on your "bad" cans and see if they now behave.

[Ace-Garageguy]

Yes, as Snake said, enamels are usually fine over lacquers, but not the other way around.

Far as the spitting goes, sometimes it's more involved than just cleaning the nozzle. There's an internal valve and a pickup tube inside the can that goes down into the paint. When these cans sit for a long time, the pigments settle to the bottom. Solid pigment can get up into the tube, and clog it, or the valve, inside the can. It may spray fine for a minute or 2, but the solids can clump together as paint moves up the tube and cause a partial or complete clog. A partial clog internally can cause spitting.

(Image taken from open internet source under "fair-use" definition in copyright law)

I've been able to rescue quite a few cans by smacking the bottoms smartly on a hard surface (while holding the can upright). Smack, shake, smack, shake, smack, shake as necessary. The sharpish "smack" tends to knock the clog back down the tube, and shaking gets more of the solvent back up the tube to help dissolve the rest of the clog. Patience is king. Out of probably 50 cans with internal clogs, I've been able to save all but a couple.

Mineral spirits or Testors enamel thinner will work to clean your enamel nozzles. Lacquer thinner, acetone or MEK will be necessary to clean lacquer nozzles (as well as enamel).

If you CAN'T get the can to spray properly, you can always decant the paint for airbrush use.

Edited October 6, 2014 by Ace-Garageguy

[Mike Kucaba]

Nice diagram of a aerosol spray can and valve. Working for a spray valve company maintaining the machines that assembled them was a pleasant reminder of simpler times for me.

[High octane]

They are still simple for me Mike, as I'm a "rattle can" man. I find that I get good results with them, and I don't have to mix or thin paint, clean tips, clean the air- brush, check the water trap, or set the air pressure, etc.

[Pete J.]

Rattle can blues man, we all sing that tune. Bill's analysis is spot on. For that reason, I have found that it is best to store rattle cans upside down. It may look a little weird on the shelf, but that way the pigment doesn't settle around the dip tube. Also, I have found that the domed top that most cans have means that the glass marble inside will rattle around that dome a little easier and mix the paint quicker that it banging into the dip tube at the bottom. Also, if the valve leaks it just lets the propellant escape and doesn't leak paint all over. You can always decant the paint out of a rattle can even after the propellant it gone and it will be usable in an airbrush.

Just a couple of tips from someone who has been using these things a while.

[Cato]

For that reason, I have found that it is best to store rattle cans upside down. It may look a little weird on the shelf, but that way the pigment doesn't settle around the dip tube.

I have too. I figured it was right-side-up at the store for at least a year and thought any sediment should be moved off the bottom. Good ol gravity.

On a separate note, I had a (new) can of Duplicolor spit out its small white nozzle. This while coating my carefully prepped Rolls fender. Thankfully I always start off the subject and move the spray over. Shot clean off and hit the overspray curtain (drop cloth) I use. No spatter on the part.

The counter guy at the parts store exchanged it with no problem.