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HVLP Spray gun problems

Well today I got started spraying some Shellac on the Cedar Chest. But boy was it a challenge. I have taken the spray gun apart at least five times today and gone through it completely. I was having a problem that is driving me crazy.

When I pull the trigger I get a blast of spray, but then it is like it can't get any out of the cup, (which is on the top) and there is almost no Shellac coming out. Each time I pull the trigger, I get the blast then nothing much.

This is a HVLP gun from Woodcraft. I have used it and never experienced this problem before. It was cleaned and put away before Christmas when I last used it.

I have cleaned the filter between the cup and the gun. I even took it out just to see if it was keeping it from flowing down into the gun. I poured all of the shellac through a strainer before putting it into the cut.

I have run the air up and down, adjusted the amount of product delivered and I am lost.

It almost act like there is a vacuum on the cup and the material doesn't feed down fast enough.

Any ideas? I am open to try anything.

John Moody
John Moody Woodworks
http://www.johnmoodywoodworks.com

Tags: HVPL, Shellac, Spray Gun, Spraying Problems

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JourneymanPermalink Reply by keith long on January 29, 2012 at 8:51am

Hey John,

Back when I made cedar chests, I used clear lacquer as a finish. I would pour a little lacquer thinner in the cup and make sure that the mist was even before I put the lacquer in. I never used shellac, but I always thinned the lacquer just a little bit and never had any problems. Have you thinned the shellac any? It wont have to be thinned very much. It may not be the problem, just a thought.

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Forum HostPermalink Reply by Gene Howe on January 29, 2012 at 9:51am

Once, a bug built a sort of cocoon in the pick up tube of my sprayer. Drove me nuts.

I would suspect that your medium is too thick. But, wouldn't running the pressure up, negate that?

The only other thing might be a speck of dried material in the system. I completely disassemble my gun and store the metal pieces in lacquer thinner in a tightly capped 1 qt. jar.

Gene
'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

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Site AdminPermalink Reply by John Moody on January 29, 2012 at 10:02am

Thanks for the suggestions. I am going to reassemble it here in a little bit and try again. I'll let you know if I find anything. I have sprayed this same mixture before without problems but I could thin it a little if needed. I increased the pressure and tried even lowering It to see if that had anything to do with the problem. Since I usually spray shellac with this gun I keep it in DNA till I use it the next time.

Make be the gremlin left last night.

John Moody
John Moody Woodworks
http://www.johnmoodywoodworks.com

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Master CarpenterPermalink Reply by Richard McComas on January 29, 2012 at 11:29am

Are you 100 % sure the little breather hole on top of the cup is clean/clear? I have Jeff's book and video (worth having) on spraying and trouble shooting spray guns. I says that 90 % of spray problem with a gravity feed guns is that little hole on top of the cup is dirty of plugged.

http://www.amazon.com/Spray-Finishing-Simple-Step---Step/dp/1600850...

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Site AdminPermalink Reply by John Moody on January 29, 2012 at 3:11pm

Richard you are right on. I thought it was clear but after soaking it all night in DNA I ran a pin through the hole and got a small piece of dry finish right in the place where it makes a 90 degree turn. After clearing that it sprayed like it should. It just wasn't getting enough to allow it to flow as it should. I could get some air through it when I blew on it, but it was not enough to let the liquid flow. I was getting some finish out, just not enough to do a good job.

Thanks for all of the suggestions and help. I know I will pay more attention to that in the future.

John Moody
John Moody Woodworks
http://www.johnmoodywoodworks.com

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Master CarpenterPermalink Reply by Richard McComas on January 29, 2012 at 4:35pm

John, next time you stop at a auto parts store asked the if they have "105 gun and equipment cleaner". That what I've been using for cleaning my guns after using shellac and waterborne products. Work really well and won't hurt the plastic and nylon parts in your gun. It the bes cleaner I've found for the waterborne finishes.

John Moody said:

Richard you are right on. I thought it was clear but after soaking it all night in DNA I ran a pin through the hole and got a small piece of dry finish right in the place where it makes a 90 degree turn. After clearing that it sprayed like it should. It just wasn't getting enough to allow it to flow as it should. I could get some air through it when I blew on it, but it was not enough to let the liquid flow. I was getting some finish out, just not enough to do a good job.

Thanks for all of the suggestions and help. I know I will pay more attention to that in the future.
John Moody
John Moody Woodworks
http://www.johnmoodywoodworks.com

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Site AdminPermalink Reply by John Moody on January 29, 2012 at 6:42pm

Thanks Richard, I will be sure to pick up some of that tomorrow.

John Moody
John Moody Woodworks
http://www.johnmoodywoodworks.com

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Site AdminPermalink Reply by John Moody on February 5, 2012 at 7:30pm

Richard, do you know which auto parts store you got this at? I went to three different ones in our area and they had no idea what I was asking for. I even pulled up your picture and let them see it.

Richard McComas said:

John, next time you stop at a auto parts store asked the if they have "105 gun and equipment cleaner". That what I've been using for cleaning my guns after using shellac and waterborne products. Work really well and won't hurt the plastic and nylon parts in your gun. It the bes cleaner I've found for the waterborne finishes.

John Moody said:

Richard you are right on. I thought it was clear but after soaking it all night in DNA I ran a pin through the hole and got a small piece of dry finish right in the place where it makes a 90 degree turn. After clearing that it sprayed like it should. It just wasn't getting enough to allow it to flow as it should. I could get some air through it when I blew on it, but it was not enough to let the liquid flow. I was getting some finish out, just not enough to do a good job.

Thanks for all of the suggestions and help. I know I will pay more attention to that in the future.
John Moody
John Moody Woodworks
http://www.johnmoodywoodworks.com

John Moody
John Moody Woodworks
http://www.johnmoodywoodworks.com

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Master CarpenterPermalink Reply by Richard McComas on February 5, 2012 at 8:35pm

John, I get mine a "Carquest Auto Parts.

John Moody said:

Richard, do you know which auto parts store you got this at? I went to three different ones in our area and they had no idea what I was asking for. I even pulled up your picture and let them see it.

Richard McComas said:

John, next time you stop at a auto parts store asked the if they have "105 gun and equipment cleaner". That what I've been using for cleaning my guns after using shellac and waterborne products. Work really well and won't hurt the plastic and nylon parts in your gun. It the bes cleaner I've found for the waterborne finishes.

John Moody said:

Richard you are right on. I thought it was clear but after soaking it all night in DNA I ran a pin through the hole and got a small piece of dry finish right in the place where it makes a 90 degree turn. After clearing that it sprayed like it should. It just wasn't getting enough to allow it to flow as it should. I could get some air through it when I blew on it, but it was not enough to let the liquid flow. I was getting some finish out, just not enough to do a good job.

Thanks for all of the suggestions and help. I know I will pay more attention to that in the future.
John Moody
John Moody Woodworks
http://www.johnmoodywoodworks.com

John Moody
John Moody Woodworks
http://www.johnmoodywoodworks.com