Need Nitro Lacquer spraying advice

[Mike Dowell]

I know this is long and splattered and I DO apologize for such a crazy post that you're about to read but right now I'm feeling like I have no idea how to spray, and after having sprayed probably 60 successful finishes in the past, I'm just clueless on what has gone wrong. Please do read.

Long story short - I sprayed this huge dining table with (2) 18" leaves using my Earlex 5500 with 1.5mm tip/nozzle set. One half of the table (not leaves) turned out like garbage while the other three sections look amazing. Same sprayer, same lacquer, same measured thinning. I'm out in left field on this one. Now I've got so much finish that I have to re-strip this side of the table and start over new. What happened was there were a couple areas that had many, many tiny little bubbles - like a texture. I tried sanding that out which resulted in tiny little white dots where the bubbles were. Using the old rule "one coat of lacquer dissolves the previous coat" I sprayed another coat. White spots still there. I tried spraying straight lacquer thinner with a touch of lacquer and that coat turned out horrible - so horrible - it looked awful. I sanded all of that down with 220grit.

Fast forward:
Many folks on here have spoken good things about ML Campbell products so I gave them a call for some technical questions about some of their products such as MagnaLac. The woman I spoke with sounded like she could have been a chemist who has been spraying finishes for 20 years - she was amazing. After I got through all my questions about Magnalac and a few other of their products, I asked her about the problem I was having with NC lacquer. She suggested that thinning 50/50 doesn't leave enough solids and that realistically, I shouldn't be thinning AT ALL. She suggested spraying the NC lacquer as well as Magnalac straight - no thinner. So, as an experiment, I loaded up my sprayer with NC lacquer and no thinner. It sprayed in huge dots and left an insanely thick finish - it is so horrible, I am going to strip that half of the table. - here is a list of questions(sorry):


1) Did the straight lacquer come out in droplets because the tip/nozzle was too big/small?
2) Is 50/50 way overboard thinning?
3) should I be spraying straight, un-thinned finish?
4) did my results get worse and worse because there was so much finish built up on the table?
5) How far away do you spray from the piece? I average 3-4 inches (is that bad?)


I'm lost. I've sprayed so many pieces of furniture - mostly with good results. This one baffles me. I've had consistently good results from my Earlex HVLP setup until now. One thing that I often wonder about is why my sprayer works best with the volume knob turned almost all the way down. If I open the volume knob any more than 1 1/2 turns, the finish just BLOWS out of it. It's insane.

Again, sorry for a post which has multiple problems to solve and many questions. I'm feeling scatter-brained right now.

Thanks!

[John Coloccia]

Most nitros come ready to spray. Some people thin 10%. 50% is very excessive for any nitro I've ever seen. The 1.5mm tip is larger than I prefer. I like somewhere in the 1.3mm range or so. That said, 1.5mm is not excessive but it's not my personal preference. 3-4 inches away is too close. 6" or so...maybe a touch more depending of your settings and technique...is better.

But I don't think any of this is causing your problems. Take that gun apart and clean it like you've never cleaned it before. Clean the cup until it's clean. Not OK clean, or sorta clean. Clean so you can drink out of it. Ditto for the rest of the gun. Make sure the packing is still serviceable, i.e. hasn't become hard from neglect and dried finish. If it is, replace it. Then reassemble the gun, lube the packing with paint gun lube and make sure the nut is properly adjusted (tighten it until the needle hangs up, and then loosen it slightly until the needle just barely moves freely and smoothly.

And then shoot your nitro again, either unthinned or thinned about 10%, and you'll get good results

THEN, if you want to make your life easy down the road, invest in a disposable liner system, like DeKups or the 3M PPS. You won't ever have to clean the cup again, you'll be able to shoot at any angle...even upside down...and your entire cleaning routine will become much easier. That's assuming you have a gravity fed gun, but most are these days.

[Mike Dowell]

Thanks John!

One thing I wanted to ask is about how the finish was coming out in huge drops. Due to dirty gun? Is it normal with that sized tip to have to turn the volume knob mostly all the way down?

Oh, and how do I tell if the packing is serviceable?(haven't heard that term sin the USMC)

This is a new spray gun - about a month old. And it's siphon, not gravity.

[John Coloccia]

Thanks John!

One thing I wanted to ask is about how the finish was coming out in huge drops. Due to dirty gun? Is it normal with that sized tip to have to turn the volume knob mostly all the way down?

Hard to tell. It depends on the gun, really. Just put that fluid control wherever it needs to be. I'll bet that the large drops are due to leaking at the packing. Spittiing and/or pulsating are one of the possible signs that there's a problem at the packing. This is often the problem, not because it's something difficult to adjust or a high maintenance item, but because it's very often neglected by people that don't do this for a living. It's one of those things that get ignored until it causes a problem. Also, if you see any finish at all that's leaking at or around the trigger, the packing is almost certainly the problem.

And it can also be due to a dirty gun. That's the other thing that gets neglected. Guns need to be in near pristine condition to function properly. Leftover bits of finish can come loose and clog things up, or even spit out onto your work. The tiniest bit of finish on the needle or the cap can completely screw up the atomizing. My gut tells me that all of your problems are just due to a dirty gun.

This happens to everyone, though. No one cleans perfectly. Every now and then, I need to take a gun apart because it's shooting poorly, and just clean the bejeesus out of it because I missed something. It's not so bad with nitro. Just clean with lacquer thinner and you're good to go. Just try getting a gun clean that previously sprayed 2 part, fluid resistant epoxy primer. You may as well just put on a hazmat suit and go at it with MEK at that point. I've had to do that, and it's NO fun whatsoever!

[Rick Mosher]

All finishes are not packaged the same. Some are thick, some are thin and it also depends on temperature. Whats sprays great out of the can in the summer at 90 degrees can spray like crap when it is 35 degrees. Viscosity varies with temperature and HVLP type spray guns don't spray thick paint well, it won't atomize properly and you get horrible orange peel. I don't use an Earlex system but have used turbine style sprayers in the past. The ones I used had heated air coming out which dried the finish very fast, that can cause the finish to dry on the tip while you're spraying and then drops will form and blow off on the finish. The way to avoid that is to constantly clean the tip with clean solvent as often as is needed. I think I have heard people say the Earlex comes with a viscosity cup? If it does you need to use it with a stop watch and find the viscosity that works the best with your gun. Then if you check it and it is way longer you need to add thinner until you get to the proper viscosity. The Kremlin system I use would spray most finishes right out of the can but a siphon fed turbine system will not. For a conventional nitro lacquer 50/50 sounds reasonable but you need to check with the viscosity cup to be sure. With lacquer adding too much thinner can effect the sheen (make it a little duller) but it will not hurt the integrity of the finish.

[Mike Dowell]

Alright - now I am thoroughly confused - and it has everything to do with viscosity.
Here is the info sheet for the lacquer I am spraying - http://www.benjaminmoore.com/Downloa...eet_file_en_US

It says viscosity - ready to spray. John is saying to thin no more than 10% and Rick says 50/50 sounds about right. I'm not sure why, but I'm totally confused and lost on this now.

I WILL say that I've had good results with this sprayer at 50/50 but to be fair, when I created this thread, everything had gone downhill. I have cleaned the living heck out of the spray gun now but haven't used it again yet. When I looked in the cup, the mixture inside had skinned over. I'm certain that my issue is a dirty gun only because in the past I've gotten wonderful, effortless good results with this new sprayer. But, now I'm confused about viscosity.

If I'm being honest (which I tend to naturally), I'm going to announce that I've done some 5 star spraying in the past but I can't tell you exactly how. It seems like sometimes I cam just mist some lacquer on to a piece and it looks great - no matter the angle, distance from work, etc... But I couldn't tell you how I had it set up.

This new Earlex 5500 HVLP rig is dead simple. It doesn't even have a fan control knob - nope. It has only a volume knob (I call it a volume knob but it is the knob that controls how far the pin can travel backwards). You just fill the cup and spray. But now, it doesn't seem so simple.

Turbine powered HVLP rigs are the way to go aren't they?

[John Coloccia]

It says viscosity - ready to spray. John is saying to thin no more than 10% and Rick says 50/50 sounds about right. I'm not sure why, but I'm totally confused and lost on this now.

"Ready to spray" means that the viscosity is appropriate for spraying, as opposed to some other viscosity that are far too thick to spray. That doesn't mean it's ideal for your situation. It will always be on the heavier side. If they thin it too much, then it will be perfect for some people, and too thin for others. The 10% number I threw is very typical. Nearly everyone I know that's spraying "ready to spray" nitro will spray it anywhere from straight out of the can to thinned about 10%, and everything in between. It will also depend on weather, or what you're trying to do. To some extent, this is a matter of taste, style and technique as well.

So it's good you looked up the data sheet to check that it does come in ready to spray viscosity.

[Mike Dowell]

"Ready to spray" means that the viscosity is appropriate for spraying, as opposed to some other viscosity that are far too thick to spray. That doesn't mean it's ideal for your situation. It will always be on the heavier side. If they thin it too much, then it will be perfect for some people, and too thin for others. The 10% number I threw is very typical. Nearly everyone I know that's spraying "ready to spray" nitro will spray it anywhere from straight out of the can to thinned about 10%, and everything in between. It will also depend on weather, or what you're trying to do. To some extent, this is a matter of taste, style and technique as well.

So it's good you looked up the data sheet to check that it does come in ready to spray viscosity.

Thank you for the clarification. I think about this stuff when I go to bed and when I wake.

[John Coloccia]

Thank you for the clarification. I think about this stuff when I go to bed and when I wake.

I worry about small stuff too, and it's paralyzing some times. In the engineering field, we refer to it as "analysis paralysis". The thing is, with a ready to spray lacquer, and your gun setup, you should be able to take it right out of the can, spray, and have acceptable results. Maybe not ideal results, but good results. You're getting BAD results, which almost certainly means a dirty gun. All the little stuff we're talking about here with optimizing the flow control, and getting the mix just right, is minutia if you have just reasonable settings everywhere else. The problem you SHOULD be having this time of year is blush, and that's solved ideally with a climate controlled environment, and more practically with a bit of retarder added (i.e., thin it with a slower drying solvent....also known as retarder).

I really hate cleaning spray guns. It's the biggest PITA for a small shop that's not dedicated to doing such things. I don't think there's anyone who sprays that doesn't run into this sort of nonsense. It just kind of comes with the territory. They're just very finicky sometimes.

[Bob Wingard]

ALWAYS use a viscosity cup, and know what your gun LIKES to shoot. The manual should give you a good starting point, and you shouldn't have to deviate more than a few % points from that to get perfect results ... if you do, it's likely a mechanical problem with the gun and you are trying to compensate for it with viscosity.

Your system should have come with a viscosity cup, and Earlex says it your finish should run through it at approx. 160 seconds. Good starting point.

They also recommend using Vaseline to lubricate the needle & packing glands ... keeps them soft & supple so they don't leak. Replace them as needed, which is probably a prudent thing to do at this point just as a precautionary/diagnostic measure in your situation.


http://www.earlex.com/pdf/5500-manual.pdf

[Brian W Smith]

Apologies if I missed it but.........how old is the paint?On the mechanical side...how old are your hoses?And "old" should also include any possible contaminants.

[Tony Joyce]

I guess it goes without saying, but I would strain it also. I have seen flatting paste settle and leave white specks after drying.