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Spray Gun Troubleshooting


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I shot my first coat of nitro the other day :D spraying Behlen's Qualalacq thinned 1:1 (per the instructions on the label) with my $25 detail gun (Campbell Hausfeld - looks just like the Stewmac) @ 40 psi. I didn't try to lay it on too wet and I got a fairly nice, velvety coat, just a little fine texture to it. Probably could have gotten a smoother coat by slowing the gun down and letting it get a bit wetter.

Yesterday I tried spraying it unthinned, as well as thinned 20%. I found that if I used anything less than 40 psi it would spit occasionally. It sprayed ok, but it gave me a dry coat with a lot of overspray, very fine textured but rough. I played with the psi, fluid control, making slower passes, etc. Nothing I tried seemed to make much difference, still dry coats. I was holding the gun about 6" to 8" away from the piece.

Today I picked up the 1 quart gun and gave it a try (a little easier to use than the the detail gun), but the dry coat syndrome continued, even at 2:1 lacquer/thinner.

Could it be that the Qualalacq is just too thick? (I suppose I'd describe it as thicker than heavy cream, but thinner than honey.) Or am I overlooking something? I did a search and read through several threads that discussed orange peel, but no dry coat advice. I can go back to thinning it 1:1, but everything I've read says to thin as little as possible and to use the lowest psi you can get by with.

Thanks for the help,

Mike

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Play with the pressure settings, and you're sure the gun's clean, no air leaks? What's the distance between your nozzle and the workpiece (if the distance is too great, the finish will dry before it 'hits'). What's the tip size? I found I was spraying too far away from the piece when I was getting dry coats with my new gun; you only need to be about 20cm/8" away for most of the smaller guns. Getting to know your gun and your finish takes some time.

Isn't Qualalac Behlen's padding lacquer, in theory? I know they've got properly formulated 'stringed instrument lacquer' (stewmac carries it), which might be ready to spray. If this stuff says 'dilute 1:1' on the tin, and that worked, than I'd just stick with that. Sounds like it's not formulated to spray 'as is', which is the case with all the instrument finishes I've used (Nitro, Crystallac, Target Coatings PSL and USL)

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A dry coat usually means too much air pressure, and if you can't get the coverage you want with the setting available, you have the option of going to a larger tip size, or thinning your lacquer. Like Mattia says, if thinning the lacquer works for you I'd go with that.

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Thanks Mattia & Setch,

It says "spray lacquer" right on the tin, and the instructions say 1:1 for spraying @ 35-55 psi. I emailed and left voicemail for the tech people at Behlen, no response yet (it was late on Friday :D ) I believe the spray tip is 1.8 mm, and the gun is rated for "very low to medium viscosity" finishes. I'm guessing this stuff is on the heavy side of medium. I'm keeping the gun about 6-8 inches from the piece, so I don't think the distance is the problem. It's probably just too thick to spray at the lower psi... since when are we supposed to believe the label, much less read the instructions? B)

(treating you both to a virtual steak dinner for all your help... :D)

Mike

edit: I've read opinions on the Stringed Instrument Lacquer that say it's intended more for acoustics, i.e. the extra flexibility isn't necessary for solid bodies and whatever plasticizers or voodoo they use tend to make it a slightly softer finish... Not that it wouldn't work, but that's why I went with the Qualalacq - supposed to be a harder finish.

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I hate to state the obvious, but why do you feel it necessary to try to do it different than the directions clearly state? I mean, what's up with that? B)

You're simply making your own problems for no good reason. Follow the directions, thin 50/50, and be Happy Camper No. 1 once again.

I thin 50/50 for 11 years now, a little thicker sometimes, and I live a trouble free existence.

BTW, there are numerous threads on the MIMF on ways to reduce thinner amounts, most of the successful ones involve heating the lacquer before you put it in the can to shoot it (which thins it). I find all that stuff unnecessary and a little dangerous myself and just follow the directions and have no problems (well, guitar-related anyway :D )

BTW No. 2, I would highly recommend you buy some retarder and learn how to use it (very sparingly).

I ALWAYS use retarder, but very very little, like maybe 1/2 teaspoon to a jamb gun batch, and add it to the thinner and stir before you add the lacquer and stir some more. This will help your 'dusty' issue.

Don't make things unnecessarily hard on yourself for no good reason, there are enough real problems out there to solve than to make your own up as you go, hehehe. :DB)

:D

Here, let me say it another way:

You're trying to figure out the finer points of professional suspension/handling characteristics for an Indy track racer when in reality, you don't even have a liscence to drive a regular car on regular pavement yet.

Just start out normally following the directions, they're there for a reason, if you want to do rad custom stuff later on after you learn basic shooting 101, then fine, but you're putting yourself WAY ahead of your own game right now.

Realize honestly where you're at and start from there, you'll progress much faster like that.

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Hehehe... chastized by the Dark Master himself! :D

Actually (in my humble defense) I started out following the directions... and was advised by the experts to stray and try it unthinned. Oh well, it didn't work. No harm, no foul...

I don't mind at all using thinner - if it needs it, great. Some of the troubleshooting guides I've read address problems caused by the lacquer being too warm - not going there!

I get the retarder/flow out thing. Does that little bit of retarder affect your cure time much? I definitely don't need it due to humidity issues - my spray room is at a constant 30% - 40% humidity and 70° F.

Drak, what lacquer are you shooting these days?

Thanks for the advice, and the colorful analogy :D

Mike

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Well, experts can get caught up in their own shoelaces sometimes if you know what I mean :D .

When I give advice to someone just starting out, I try to speak to them where they're at, not make them meet me where I'm at...that's not teaching, that's just useless knowledge if the person doesn't have the experience you have and can't understand ehh, 'progressive' concepts yet, or why someone might try to use them.

Using warmed lacquer is definitely an advanced concept, and one I find no need to pursue, some people just like to push the envelope for the fun of it, but they've probably mastered all the basic stuff for years already. There's nothing wrong with it if you understand what your doing and why it works, but I would never ever tell a first-timer to try going without any thinner, that's ridiculous advice.

Retarder slows down dry time yes, that's one reason it will cure some of the issues of a 'dusty' finish, it gives the lac more time to flow out, which I personally like, I use it reguardless of the humidity, although I do use more when it's humid. Just a very little bit tho...too much and the finish will never harden properly, but used in the right amounts, it's a nice additive.

You may experience that you don't need any if you just go back to using thinner tho.

BTW, in case you didn't know this, there are different grades of thinner...you're not supposed to use lacquer thinner from Home Depot, that's referred to as 'trash' thinner, it's cheap and not intended for nice nitro jobs.

Find a finish supply store and get a nice medium-speed thinner designed for shooting nitro with :D .

I shoot Lenmar lacquer, it's what my local finish supply store carries.

PS, I shoot anywhere from 20 to 35 PSI w/ my jamb guns, and as little as 7-10 w/ airbrushes.

Too much psi and I get too much overspray and/or spraywave, which to me means more product I paid for uselessly flying off into the atmosphere and not laying coat on my guitars.

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Just an FYI update...

I got through to tech support at H. Behlen Co. today.

The gentleman I spoke with believed the 1:1 thinning instructions on the label are an out-of-date holdover. He recommended thinning it 25%, and commented that it might be possible to shoot it unthinned depending on the spray equipment.

I'll err on the side of more thinner.

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I agree with that. You could make 25% work under the right conditions, I would opt for a bit more, but experiment until you find your recipe.

Everything is relative to your gun, your climate, your techniques, etc. :D

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Update...

The 1:1 ratio @ 20-25 psi seems to work best, maybe a tad bit more pressure to get less orange peel.

I was able to get the detail gun to spray it at 2:1 lacquer/thinner @ 25 psi, but the material is just too heavy (even with a 1.8mm tip)... excessive overspray, dry coat, and the material tends to concentrate in the middle of the pattern. I can get it to wet down, but the edge of the fan is all dry overspray. More pressure would just make it worse.

I'm sticking with the 1:1 mix. :D

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It's your option whether you want to use it or not, you don't have to, but a smidgen of retarder in your mixes would probably fix your 2:1 drycoat-on-the-edges problems and allow you to use your higher lac-to-thinner concentration.

You can get retarder in pints, and a pint would last you several years probably, you use it verrry sparingly, but I always use it. :D

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Are you saying you use flowout additive, or just that your lac flows out well with no thinner?

PS, some manufacturers sell pre-thinned lacquer, so you wouldn't need to thin it.

Also, that statement doesn't help guys that are trying to understand the basics of shooting lacquer unless you give them a much more thorough explanation of how your system is set up, because reading your post, a newbie could be under the assumption that one normally could do that, and most people don't do that, so qualify your post a little better for clarification to those who could use it.

In other words, if you're going to throw out information like that under the assumption that a newb will go out and try it on your recommendation, then validate it with some in-depth details about your methods, because most poeple aren't doing what your doing. :D

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Fair point.

The stuff I've used is formulated for spraying 'straight', which many instrument-specific finishes are; local nitro, Target's USL, PSL waterbased finishes, Crystallac long ago. All tins say it can be thinned to about 10%, but it's ready to shoot as-is. I don't use any flowout additives, additional thinners, nothing. I used to thin about 10% with my old (lousy) gun, but the new one (SATA MiniJet 3) handles stuff fine, gets it on smoothly, only scuff sand between shooting days to break the surface, and tend to level-sand once, immediately prior to the last two coats. Unless I've gotten unlucky and sprayed badly (generally a technique problem), creating drips or other surface irregularities.

I found that getting the pressure, fluid feed, spray distance and feed rate right fixed any problems I had. No need to go mess with finish composition. I guess all I'm trying to say is that you shouldn't assume you need retarder, thinner, anti-fisheye stuff from the git-go. It depends on your gun, your technique, and quite importantly, your environmental conditions (temp, humidity). All can affect finish flowout and final results. And so can finish composition itself, of course. I've actually got more experience with waterbased stuff than with nitro, and it's generally slightly more quirky stuff (you gotta strain, make sure everything's perfect, and lay on just the right amount..). Might move back to Nitro, or maybe Rustin's Plastic Coating, now that I have a view on a spray location that's not in an urban area...

That should cover the bases ;-)

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A nice spirited debate never hurts :D

I noticed last night that the thinner label has the same instructions as the lacquer. Curious that they wouldn't update their labels if in fact they now recommend a different method. It is pretty thick looking stuff straight out of the tin - I'm fairly well convinced it's not "ready to spray". Wonderful stuff for drop filling. I'd be interested to see how the viscosity compares to their Stringed Instrument formula.

It flows pretty well at 1:1 as long as I go slow with the gun and wet it out a bit. That takes a bit of practice after using rattlecans, which don't afford you the luxury of slow passes.

I'll take the retarder under advisement, but I'd prefer to save it as a last resort - a bit skittish about doing anything to increase the cure time.

Thanks, guys. :D

Mike

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I found that getting the pressure, fluid feed, spray distance and feed rate right fixed any problems I had. No need to go mess with finish composition. I guess all I'm trying to say is that you shouldn't assume you need retarder, thinner, anti-fisheye stuff from the git-go. It depends on your gun, your technique, and quite importantly, your environmental conditions (temp, humidity). All can affect finish flowout and final results. And so can finish composition itself, of course.

-Very- well said, and sooo true. :D

So, long story short, you're shooting with instrument-grade, ready-to-shoot, pre-thinned lacquer (which as already stated needs no further thinning) which if I remember correctly, is thinned from the factory about 1:1 anyway, and that, in essence, is exactly what we were discussing doing in the first place. :DB)

All instrument-grade lacquer is is pre-thinned lacquer with a tiny bit of another chemical that keeps the lac a little more flexible (which, in my experience, I think retarder also does really), ...so by using straight lacquer, thinner, and retarder, I am basically making my own instrument-grade lacquer, custom-mixed on the spot, and getting it much cheaper. You're paying them to thin it for you, and thinner is way cheaper as a product than the actual lacquer, and you pay as much for a gallon of pre-thinned as I probably do for straight pure lacquer, and I'm getting a full gallon of real lacquer, not 'cut' with (cheaper) thinner. :D

And I never insist other people use retarder, I always insert it as an option.

All retarder does is slows down the drying time, that's it, it's no 'black magic' additive. If you shoot too far away, or too dry, or under humid conditions, retarder will save the day if used properly.

Also, using the proper thinner (medium speed) is doing the exact same thing, just to a lesser extent, than the retarder does. That's what the 'medium speed' is referring to in the first place, is the speed at which the lacquer will dry on you, and the stuff you get at Home Depot, the trashy stuff, dries (evaporates, or gasses off) really quick, which isn't good. Trash for shooting.

I get the feeling that some people throw all finish additives under one big umbrella of 'unnecessary', when in reality, they all perform very different tasks and each is useful if understood for what it does.

People tend to be scared of things they don't understand, so I try to explain things in a way that removes the 'voodoo' from the product, and people really 'get' the when's and hows to use this stuff if and when they need it.

___________________________________

I noticed last night that the thinner label has the same instructions as the lacquer. Curious that they wouldn't update their labels if in fact they now recommend a different method. It is pretty thick looking stuff straight out of the tin - I'm fairly well convinced it's not "ready to spray". Wonderful stuff for drop filling. I'd be interested to see how the viscosity compares to their Stringed Instrument formula.

It flows pretty well at 1:1 as long as I go slow with the gun and wet it out a bit. That takes a bit of practice after using rattlecans, which don't afford you the luxury of slow passes.

I'll take the retarder under advisement, but I'd prefer to save it as a last resort - a bit skittish about doing anything to increase the cure time.

I believe you have what I have, straight lacquer, so thinning 1:1 is fine. As I said, I thin (really) about 65% lac to 35% thinner to maybe 2% retarder, that's as thick as I can happily get away with.

You shouldn't be scared of retarder, it's great stuff when and if you need it. I'm sure most everyone here has seen my finishes, and I always use retarder, I would not be happy if I didn't have it around, it's simply another tool in the toolkit when needed.

If I lived in Arizona, I might well not use it, the weather there is usually almost perfect for shooting.

Long story short, all these things are there to give you options. By not even considering them, you are simply limiting yourself of your options. B)

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Master Drak, you convince young grasshoppa :D

I made the trip to Seattle and picked up a quart of lacquer retarder this afternoon. I'll give the 2% retarder thing a try.

How long do you wait between coats? The instructions include a caution about allowing extra time between coats.

I've been giving it at least three hours (that is, when I've had time to shoot more than one per day :D).

Mattia - I saw a bottle of Behlen's "Qualasole" padding lacquer at Rockler today... that's probably the stuff you were thinking of. B)

Mike

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Well, I wouldn't say I do EVERYTHING 'by the book', as we already stated, it's your own special 'recipe' that counts, and that just comes with time and experience trying different things, but most of the time, I only wait about 1/2 hour between coats. I may not recommend anyone else do it that way, but that's what I do.

Having said that, I also wait about 2 months at least before my final buffouts, but then, I have 25 bodies to play around with at any given time too, so I'm never in a big hurry.

If you decide to use retarder, use (for a pint jamb gun) about 1/2 of a TEASPOON, really just a dash, that's it, that's all it usually takes to notice a difference.

I always do it like this: add my thinner to the cup first, then the retarder, then stir. Then add the lac itself and stir again.

You can up that to MAYBE a full teaspoon per jamb gun AT THE MOST for humid conditions. Past that, I think you start affecting the final hardness of the lac. I would typically never even use a full teaspoon except on really humid days, and now, I simply wouldn't bother to shoot on those days, I have 'learned my lesson' let us say.

I'm just trying to give you a feel for the right amounts so you don't make the mistakes I did years ago and use too much. B)

You really should never need more than 1/2 a teaspoon for normal conditions.

Think of retarder like this: when you realize what the 'medium speed' label means on your quality lacquer thinner can, then just think of retarder as moving your medium speed thinner down to 'medium-slow' speed.

More retarder, you now have 'slow' thinner.

Too much retarder, you now have sloooooooooooooooooooooooooow speed thinner.

Make sense? :D

:D

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Drak, you are the master! :D

I added 1/2 tsp. retarder to 4 oz. thinner + 4 oz. lacquer, 35 psi on the detail gun... It's flowing out very nicely.

Getting a good wet look in 3-4 medium-slow passes with minimal orange peel. B)

Now, if I could just solve the dust/lint problem... :D

Thanks for your help.

Mike

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Glad I could help, and glad it's working for you.

The real 'secret' is to start out with 'X' amount of retarder that works for you, then see how much you can back it down and still have it work for you, getting the amount as minimal as possible yet still effective, then stick with that. If you can use 1/4 teaspoon and still have it do the trick, so much the better. :D

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