Official Luthiers Forum!

For those who are familiar with it. I usually use nitrocellulose lacquer. As we all know, even after curing, it is possible to redissolve it in lacquer thinner. The same is not true for polyurethane. I recently started to use this kind of finish. I wonder if the spray gun has problems in clogging or what. I mean I try to clean the gun as accurately as I can. But, is it possible that if some residue of polyurethane remains in the small holes then I won't be able to clean it? For examply I noted that the thread of various elements were spoiled with polyurethane and it was pretty difficult to separate the two parts.

Yes, that is a problem with all types of "polly" finishes.That is why most auto body shops have gun washer machines.There are chemicals which will dissolve the cured residue but be careful as a some of them may eat aluminum, and they are very nasty to deal with. Its another reason most cabinet shops have converted to air assisted pressure feed spray systems like Kremlin rather than more conventional atomizing equipment. That is a main reason I used only harbor freight guns for so long, they are disposable. When they got a little too dirty I'd just toss em. On my Apollo system, I completely break down the gun and thoroughly clean every time I am done or once a day, depending. All parts get a soak in proper solvent and scrub with soft brushes. Cans of carb cleaner from the auto store with the straw on them are used to clean out the small passages. Never insert hard tools like paper clips into the internal passages to try and clean them, minute damage to these can ruin a gun and cause malfunction.

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Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

For any catalyzed system you will probably want to have a jar of methylene chloride on hand to occasionally soak the metal parts of your gun. Note....methylene chloride is the NASTIEST stuff you'll come into contact with...so suit up properly when handling it. Methylene chloride is the basic chemical in paint strippers. You can buy Jasco at Home Depot, or instance. Pour a little Jasco in a GLASS jar and soak your metal parts overnight. Jasco will break down most plastics so don't soak plastic parts if you want them to be there in the morning. Swish the metal parts around in another jar of acetone to remove the Jasco.

As Brian said.....use a fairly cheap HVLP gun to shoot with. Clean the gun thoroughly after each session with acetone by using a half a cup of acetone and shaking the gun as you spray it out. Repeat this two more times and the inside of the gun will be pretty clean. The metal parts only need to be cleaned with Jasco rarely. The pin and the orifice are the critical parts on the gun. Keep them clean and a cheap gun can last quite a long time. I'm spraying with a ten year old gun today. I've put every kind of chemical through it....and I've used it a LOT. Of course...use a cheap gun and don't be afraid to throw it away and start with a fresh one.

Also...strain your finishing material as it goes into the gun. Often contaminates are the cause of the spraying problems you described.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic