Cleaning a Spray Gun

[Mr Eddie]

I'm going to be spraying some shellac soon and wondered what to use to flush/clean the gun after spraying?  I've got an HVLP gun with the pressurized PPS cups.  Do you let the gun set in between coats?  How long after spraying can I wait before clean up?  Thanks for the help.

Lonnie

[Gibbcutter]

Denatured alcohol & ammonia

[Snipe Hunter]

A good habit to develope:

Wipe off the spray tip between coats. The needle protrudes through the tip a little so wiping off the tip will also clean the tip of the needle. Use whatever you'd use to clean up shellac. Denatured alcohol, ammonia? I'm not a shellac guy so I wouldn't know but if that's the stuff, use it. I use lacquer thinner for the types of finishes I shoot. I use Bounty paper towels. They're cheaper than the blue shop towels, no lint and durable. Cloth can leave lint on the tip which will look nasty on your workpiece. Cheap paper towels will tear and leave lint in the tip. IMHO, it's critical to keep the tip and needle clean to achieve and maintain good atomization. Maybe more critical than keeping the inside of the gun clean. You mught consider removing the spray cap once in a while and clean it too.

[fredhargis]

You will want to use ammonia. The DNA only dilutes the shellac, and may leave some trace of it behind. It also costs more. The ammonia (household ammonia) absolutely destroys the stuff and leaves your gun squeaky clean. A small amount of it in a 5 gallon bucket with some warm water does well, and there's no hazardous cleaner to dispose off. Do rinse the gun  thoroughly and be aware, ammonia can stain aluminum (at least it did on one of my guns). The stain isn't damaging, but it does show....in my case it happened when I let the cup soak a while.

[Bill Wilson]

You will want to use ammonia. The DNA only dilutes the shellac, and may leave some trace of it behind. It also costs more. The ammonia (household ammonia) absolutely destroys the stuff and leaves your gun squeaky clean. A small amount of it in a 5 gallon bucket with some warm water does well, and there's no hazardous cleaner to dispose off. Do rinse the gun  thoroughly and be aware, ammonia can stain aluminum (at least it did on one of my guns). The stain isn't  damaging, but it does show....in my case it happened when I let the cup soak a while.

+1 on the ammonia.  I have a couple guns that only are used for shellac.  I shoot a little DNA through them when I'm done spraying and a little when I'm getting started the next time and haven't had any problems, but I think I may try diluted ammonia next time.  I use ammonia for cleaning shellac out of measuring cups, brushes, etc, but haven't used it in the gun.  Once I let the cup soak in it for awhile and it did etch the aluminum.  I was 1/2 afraid to run it through the gun after that, so I never did.  


Is ammonia hard on O-rings and seals at all?

[jteneyck]

I start with DNA to flush the gun a few times while it's still all together, then disassemble the gun and put everything in warm water with about 30% ammonia in it.  If you start with ammonia it will turn the shellac white and some of it will stick inside the gun making it harder to clean. 

My gun has a nasty habit of overspray accumulating on the air cap horns, so I take it off after every spray session and dump it in lacquer thinner, which works with shellac, WB paints, etc.  I wipe the N/N with lacquer thinner, too, with a blue shop towel. 

I clean the PPS liners/lids the same way as the gun.  Start with DNA to remove most of it, then warm water + ammonia.  Or throw them away.  Stuff that gets on the outside of the PPS cup I clean with lacquer thinner or a water/ammonia soaking.  

John

[Bill Wilson]

I start with DNA to flush the gun a few times while it's still all together, then disassemble the gun and put everything in warm water with about 30% ammonia in it.  If you start with ammonia it will turn the shellac white and some of it will stick inside the gun making it harder to clean. 

My gun has a nasty habit of overspray accumulating on the air cap horns, so I take it off after every spray session and dump it in lacquer thinner, which works with shellac, WB paints, etc.  I wipe the N/N with lacquer thinner, too, with a blue shop towel. 

I clean the PPS liners/lids the same way as the gun.  Start with DNA to remove most of it, then warm water + ammonia.  Or throw them away.  Stuff that gets on the outside of the PPS cup I clean with lacquer thinner or a water/ammonia soaking.  

John

Good info.  Thanks

[fredhargis]

Is ammonia hard on O-rings and seals at all?

I haven't seen any damage to them, but that doesn't say it won't. Same as with the aluminum parts, don't soak them too long and they should be fine.

[Mr Eddie]

Thanks for all the replies - that's exactly what I wanted to know.

Lonnie