Cleaning the Spray Gun

Secrets from the auto-body side. March 18, 2005

Question
My last build required alot more finishing then most of my previous projects. It seems like I spent more time cleaning the guns than spraying finish. I don't spray a lot mostly because I don't like spending all that time cleaning. I am asking for some help or tips to speed up the cleaning process. I spray only WB, mostly paint or poly. Most of my work consists of small projects and custom sized pieces.

Forum Responses
(Finishing Forum)
From contributor J:
I would suggest getting a nylon bristled brush and keep it in a cup of water (lacquer thinner when using solvent borne coatings) and periodically clean the tip. It's a lot easier to keep it clean as you're going along than to get rid of all the build up. Check your pressure settings as well to see if that is contributing to the build up.

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From the original questioner:
Do you take it apart every time and clean the needle, tip and air nozzle? Or is pulling the needle and running hot soapy water through the gun for five or ten minutes followed by a good rinse good enough?

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From Paul Snyder, forum technical advisor:
Describe the process you use to clean the spray gun. Cleaning shouldn't take much time so it'll help to find out how you're doing it to see why it takes so long.

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From contributor C:
I clean my gun with a garden hose if I can. This works very quickly in decent weather. I have a nozzle that has a jet stream setting with a small nipple that fits into the feed tube. I stuff the nozzle tip into the feed tube and open it up so that I get a high volume high pressure stream of water through the nozzle. The cup I turn upside down and rinse out with the hose. Occasionally I use a brass brush and a pistol cleaning rod to clean the inside of the feed tube (I dip the brush in a little lacquer thinner). Once in a while I will wipe the cup lid and inside of the cup with a rag dipped in lacquer thinner but only about every sixth cleaning or so.

The garden hose will do the job very fast and quite well if you get it right after spraying. It gets to be more work if you put it off. I can usually clean up in about fifteen minutes. If I am spraying multiple coats I only clean up at the day’s end (except for a quick rinse when changing colors). It depends on what you spray but sometimes I leave paint in the gun overnight and continue spraying the next day too. I clean the nozzle exterior each time I set the gun down (just use a damp rag for this).

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From contributor A:
I would suggest that you check out the 3m PPS system for replacing the cup on your gun. We did this and fell in love with it. We use 99% water-based and here's what we do:

1. Use the snap on cup for whatever we are spraying.

2. During spraying we keep a tooth brush sitting in a cup of water and clean the tip about every 5 minutes

3. When we are done we unsnap the cup with finish in and snap on a cup filled with distilled water. Let it run through the gun and leave it on until we start spraying the next coats an hour or so later.

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From contributor D:
I really like the PPS system by 3M. On solvent wood coatings this isn't a big deal as solvent wood coatings clean effortlessly using lacquer thinner; with waterborne it's a nightmare.

You should seldom need to tear the gun down. Use the "perking" technique first developed by Sharpe for use with gravity guns and you will eliminate the need to tear down most of the time.

Here's how perking works. You dump out whatever coating is in the gun. You add solvent, you loosen the air cap from the gun so that's is just about hanging off the gun but not quite. You turn down your air pressure to about 10 PSI and you pull the trigger. You cover the top of the gravity cup with a rag. The gun will now percolate like an old style coffee pot and clean itself very nicely. Continue this for about 30 seconds. Dump out the solvent, wipe the gun off and you're done.