The Ford Barn

mrtexas · 03-18-2016, 07:46 PM

A while back I shot some varnish thru my spray gun when my wagner failed. I can't be sure that caused the problem as the problem didn't show up immediately afterwards. Now I'm having trouble with spraying out epoxy primer. On some pieces it is globbing up and not sticking like the surface is contaminated with oil or? I sand down the affected area and spray it again. Sometimes it is OK and other times the same problem. I thought I thoroughly cleaned the gun out. Sometimes when I spray over a bad spot after sanding it is OK and other times it does the same globbing. After getting the epoxy on successfully and spraying the 2k or urethane I don't have the same problem. I'm using epoxy from Southern Polyurethane Inc.

I've done the following to try to solve the problem:

1)changed the air compressor filter
2)bought new air hose
3)used wax and grease remover
4)changed cans of primer and activator
5)soaked the spray gun in thinner overnight
6)used only new thinner to clean out gun, I had been re-using old thinner on the first rinse of the gun before using new thinner to finish the cleaning
7) took apart more of the gun than usual while cleaning
8) some affected parts had soaked in evaporust
9) carefully drain water from tank before spraying
10) I'm throwing out whatever I can think of I've done lately as I am stumped.

I'm beginning to think it might be silicone contamination but I don't use silicone that I know of. I have a can of a special silicone remover and used it on a piece after sanding off all the primer from the first failed spray that had a real mess of primer on it.

Comments? Anyone use a special silicone remover?

flathead48 · 03-18-2016, 08:12 PM

Mrtexas have you spoken with the guys at SPI, they are very helpful and knowledgeable. I have used their epoxy and their clear and not experienced your problem but it does sound like some contamination .

Kahuna · 03-18-2016, 08:13 PM

Soak the the gun in Lacquer thinner

john worden · 03-18-2016, 08:26 PM

Was the varnish oil base? Sanding can grind contamination into the surface.

hulleywoodworking · 03-18-2016, 08:32 PM

You need to tear the gun down COMPLETELY and clean every part, first in lacquer thinner then in the Urethane Reducer from SPI. Put it back together and spray some SPI Urethane Reducer through it.

Rinse out your measuring cups and whatever container you are mixing the epoxy in, again with the SPI reducer. Mix your epoxy, let it induce for at least 1/2 hour, then spray it. Be careful that you are not spraying too heavy a coat-the epoxy will tend to "crawl" away from itself and form craters that look like fisheye.

I keep stressing using the SPI Urethane Reducer, and only that. It is a compatibility issue-a reducer from another manufacturer may not be compatible with the SPI.

When I am done spraying, I rinse the gun with the SPI reducer, spray some through, then use what is left in the cup to clean the air cap and tip. I only do this if I will be spraying again soon; if I am done, I always tear the gun down completely and clean every part of it.

Once you do it a few times you will get pretty fast at it. I can tear down, clean, assemble, and spray thinner through any of my guns in about 15 minutes. I rarely have finish problems, and I spray pretty much everything-shellac, varnish, acrylic lacquer, post catalyzed lacquer, oil based paint, pigmented lacquers, sealers, urethane, epoxies, etc. using the same guns for everything.

Try this and report back to us.

John

mrtexas · 03-18-2016, 09:14 PM

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Be careful that you are not spraying too heavy a coat-the epoxy will tend to "crawl" away from itself and form craters that look like fisheye.

Might be it.

chap52 · 03-19-2016, 07:32 AM

Silly question...Are you running the paint through a strainer when you fill the gun?

Willit Stop · 03-19-2016, 09:21 AM

Contaminated rags can cause problems, even though they have been washed.Fabric softener,oil, grease,wax,WD-40,hand cleaner,silicone,etc. are like poison to paint.Use CLEAN rags. The panel that is being worked on may be perfectly free of contaminants but as soon as it is washed with wax and silicone remover on a contaminated rag, the whole panel will be contaminated.Fisheyes and loss of adhesion.

mrtexas · 03-19-2016, 11:06 AM

Quote:

Originally Posted by Willit Stop

Contaminated rags can cause problems, even though they have been washed.Fabric softener,oil, grease,wax,WD-40,hand cleaner,silicone,etc. are like poison to paint.Use CLEAN rags. The panel that is being worked on may be perfectly free of contaminants but as soon as it is washed with wax and silicone remover on a contaminated rag, the whole panel will be contaminated.Fisheyes and loss of adhesion.

Only use paper towels

mrtexas · 03-19-2016, 11:06 AM

Quote:

Originally Posted by chap52

Silly question...Are you running the paint through a strainer when you fill the gun?

I'm using 3m fill cups with built in strainers.

rotorwrench · 03-19-2016, 12:39 PM

Contamination can come from a lot of sources. Just running a diesel engine close to a prepped surface can cause problems. I've even experienced bad paint materials on several occasions. You just cant be too clean but I don't think a person has to go too far either. Make sure the towels you use haven't been exposed to contaminants. Any absorbent material can end up contaminated if it gets too close to other problem materials. If you suspect the paint then you can do a test on a small surface and see if it does the same thing.

03-18-2016, 07:46 PM	#1
mrtexas Senior Member Join Date: May 2010 Location: Sugar Land, TX Posts: 4,395	Painting woes A while back I shot some varnish thru my spray gun when my wagner failed. I can't be sure that caused the problem as the problem didn't show up immediately afterwards. Now I'm having trouble with spraying out epoxy primer. On some pieces it is globbing up and not sticking like the surface is contaminated with oil or? I sand down the affected area and spray it again. Sometimes it is OK and other times the same problem. I thought I thoroughly cleaned the gun out. Sometimes when I spray over a bad spot after sanding it is OK and other times it does the same globbing. After getting the epoxy on successfully and spraying the 2k or urethane I don't have the same problem. I'm using epoxy from Southern Polyurethane Inc. I've done the following to try to solve the problem: 1)changed the air compressor filter 2)bought new air hose 3)used wax and grease remover 4)changed cans of primer and activator 5)soaked the spray gun in thinner overnight 6)used only new thinner to clean out gun, I had been re-using old thinner on the first rinse of the gun before using new thinner to finish the cleaning 7) took apart more of the gun than usual while cleaning 8) some affected parts had soaked in evaporust 9) carefully drain water from tank before spraying 10) I'm throwing out whatever I can think of I've done lately as I am stumped. I'm beginning to think it might be silicone contamination but I don't use silicone that I know of. I have a can of a special silicone remover and used it on a piece after sanding off all the primer from the first failed spray that had a real mess of primer on it. Comments? Anyone use a special silicone remover? Last edited by mrtexas; 03-19-2016 at 11:47 AM.

03-18-2016, 08:12 PM	#2
flathead48 Senior Member Join Date: May 2010 Location: Saratoga Springs, NY Posts: 1,111	Re: Painting wows Mrtexas have you spoken with the guys at SPI, they are very helpful and knowledgeable. I have used their epoxy and their clear and not experienced your problem but it does sound like some contamination .

03-18-2016, 08:13 PM	#3
Kahuna Senior Member Join Date: May 2010 Location: NorCal Posts: 2,617	Re: Painting wows Soak the the gun in Lacquer thinner

03-18-2016, 08:26 PM	#4
john worden Senior Member Join Date: Jun 2011 Location: central Iowa Posts: 484	Re: Painting wows Was the varnish oil base? Sanding can grind contamination into the surface. __________________ Louvering, bias ply tire-truing, metal shaping and forming, lathe and mill work, member shop HAGERTY Ins. expert repair network. High quality paint work in Iowa.

03-18-2016, 08:32 PM	#5
hulleywoodworking Member Join Date: Apr 2015 Posts: 88	Re: Painting wows You need to tear the gun down COMPLETELY and clean every part, first in lacquer thinner then in the Urethane Reducer from SPI. Put it back together and spray some SPI Urethane Reducer through it. Rinse out your measuring cups and whatever container you are mixing the epoxy in, again with the SPI reducer. Mix your epoxy, let it induce for at least 1/2 hour, then spray it. Be careful that you are not spraying too heavy a coat-the epoxy will tend to "crawl" away from itself and form craters that look like fisheye. I keep stressing using the SPI Urethane Reducer, and only that. It is a compatibility issue-a reducer from another manufacturer may not be compatible with the SPI. When I am done spraying, I rinse the gun with the SPI reducer, spray some through, then use what is left in the cup to clean the air cap and tip. I only do this if I will be spraying again soon; if I am done, I always tear the gun down completely and clean every part of it. Once you do it a few times you will get pretty fast at it. I can tear down, clean, assemble, and spray thinner through any of my guns in about 15 minutes. I rarely have finish problems, and I spray pretty much everything-shellac, varnish, acrylic lacquer, post catalyzed lacquer, oil based paint, pigmented lacquers, sealers, urethane, epoxies, etc. using the same guns for everything. Try this and report back to us. John

03-18-2016, 09:14 PM	#6
mrtexas Senior Member Join Date: May 2010 Location: Sugar Land, TX Posts: 4,395	Re: Painting wows Sponsored Links (Register now to hide all advertisements) Be careful that you are not spraying too heavy a coat-the epoxy will tend to "crawl" away from itself and form craters that look like fisheye. Might be it.

03-19-2016, 07:32 AM	#7
chap52 Senior Member Join Date: Jun 2013 Location: Marana Arizona Posts: 1,776	Re: Painting wows Silly question...Are you running the paint through a strainer when you fill the gun?

03-19-2016, 09:21 AM	#8
Willit Stop Senior Member Join Date: Feb 2013 Location: Eureka Calif. Posts: 969	Re: Painting wows Contaminated rags can cause problems, even though they have been washed.Fabric softener,oil, grease,wax,WD-40,hand cleaner,silicone,etc. are like poison to paint.Use CLEAN rags. The panel that is being worked on may be perfectly free of contaminants but as soon as it is washed with wax and silicone remover on a contaminated rag, the whole panel will be contaminated.Fisheyes and loss of adhesion.

03-19-2016, 12:39 PM	#11
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,440	Re: Painting woes Contamination can come from a lot of sources. Just running a diesel engine close to a prepped surface can cause problems. I've even experienced bad paint materials on several occasions. You just cant be too clean but I don't think a person has to go too far either. Make sure the towels you use haven't been exposed to contaminants. Any absorbent material can end up contaminated if it gets too close to other problem materials. If you suspect the paint then you can do a test on a small surface and see if it does the same thing.