How long can water-borne finish stay in spray gun?

[Alan Lightstone]

Quick question, as I'm a HVLP newbie, and and using my Fuji gun/turbine for the first time today. Can a water-borne finish stay in the spray gun for a few hours between coatings of finish (General Finishes High-Performance, but the question would be for other finishes as well)?

I know not to leave it in the gun overnight, but I'm wondering more about 3-4 hours between coats.

[Jim McFarland]

Never used GF but I have left Target EM6000 in the gun for a couple of hours with no problems. I usually drape a damp rag over the gun which seems to keep the tip from accumulating gunk.

[Jamie Buxton]

Here's an experiment you can run. Without finish in your gun, run the system to pressurize the can. Then wait for as long as you want, and unscrew the pressure-relief knob. If you hear a little hiss, the can was still pressurized. If it is pressurized, no air has left the can, and you could have left finish in there for at least that long. When the gasket at the top of the can was reasonably new, my Accuspray gun used to hold pressure for 24 hours. The gasket is getting kinda beat up now, and probably won't hold quite that long. That said, I generally don't leave finish in the gun overnight.

[Alan Lightstone]

Can't finish dry to the outside of the nozzle, though, even though the inside finish is pressurized and not going to dry? Should I wipe the outside of the gun with some water after spraying?

[Jamie Buxton]

On my guns, there is sometimes a little lacquer left on the fluid orifice. Sometimes there's something there, but mostly there isn't. The HVLP air blows it clean. I generally dab at it with a paper towel when I put the gun down.

[Jim Becker]

I actually have left EM6000 (it's predecessor, actually) in my gun overnight without an issue...but it was really only from about 10pm to about 9am effectively. That said, I have often sprayed all day and don't clean the gun until I'm done.

[Tom Willoughby]

I have the Fuji gravity feed HVLP gun and I unhook it and put it in the refrigerator between coats so that things don't begin to set in the gun. I've had no issues so far with EM6000 and other waterborne finishes.

[Alan Lightstone]

Do I have to take apart the gun after each day's use to clean it, or can I just spray water / air or some solvent through it? What's the best solvent to clean water-borne finishes with?

[Jamie Buxton]

Do I have to take apart the gun after each day's use to clean it,

This is Fugi's gravity-fed gun, right? Fuji says you can just put a bunch of solvent in the can, back off the needle, and let it flow through. This does louse up your needle adjustment, so get used to learning how far out to set it. I use 3/4 of a turn for waterbornes.

or can I just spray water / air or some solvent through it? What's the best solvent to clean water-borne finishes with

Water.

[Alan Lightstone]

It's their 1 qt bottom-feed XPC pressurized spray gun.

[Sam Layton]

Alan, I am no expert. You will be OK leaving the finish in the gun for a couple of hours. If your gun is all stainless steel including the cup, longer times would be OK I'm sure. However, If your cup, or any parts are aluminum, you should not leave the finish in the gun over night. Aluminum and water do not get along well... I leave GF's in my gun for several hours with no problem. I have an aluminum cup.

When cleaning I use water. Then I finish with lacquer thinner, then denatured alcohol.

Sam

[Harvey Pascoe]

Mine is not HVLP but a small standard pressure gun. I leave WB finish in my gun constantly and only clean it about every two weeks or until it clogs! I spray every day, often many times per day.

[Sam Hamory]

I always fill the cup before I walk away. Less air, less drying. Usually a booger of finish will end up dried on the nozzle, I always scrape that off with my index finigernail before I attempt to spray again. If I'm spraying solvent/lacquer I'll leave it in the gun for a couple of days before I clean. Never been a problem.