Nitro Question -

VertigoCycles

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I just sprayed my first color coat on a bass I built last month. The first half of the cup wet out nicely and laid down flat but the second half went on extremely dry, like it's all over spray and it has the texture of sand paper at the moment. I'm not too concerned because I know the next coat will melt into it, but I suspect I might be in for some heavy orange peel if I don't do anything about it.

This is Cardinal lacquer, thinned out 10-15% with some white pigment and four drops of trans tint, shot through an ANI R150. I've not shot much with this gun. So far, just the sealer (also Cardinal) but that went on very nicely. I'm using the 1.0 tip, the on-gun regulator is set around 20psi and my compressor is a bit higher than that.

I'm planning on shooting some straight retarder later to flow it out and will put a few more coats of color on it tomorrow but I'd like to figure out why everything changed halfway through today.

FWIW, I shot this outside in the shade and it was about 95° and 25% humidity.

I'm still very much a novice, and will be forever because I don't build enough guitars to get very good at spraying, but I take advice well.

So, why the change half way through the session?
 

jfgesquire

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When you went outside, how long was your paint also outside? Did your paint slowly warm up from inside temperature to outside temperature?

Do you have a large air tank? Compressor? Did it refill your tank while you were spraying?
 

VertigoCycles

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Paint was in the shop all day, which is not conditioned and is usually very similar to outside temps. I forget how big the tank is, but it's "big" about 4.5ft high and the compressor did not kick on while spraying
 

Drak

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When's the last time you cleaned the tip orifice/assembly?
Could have been a clogged (or clogging) tip.

Anyone who shoots regularly would see/sense a clogged tip immediately and stop.
But if you don't shoot a lot...you could miss the clue.

And anyone who shoots regularly is very used to cleaning their guns regularly.
And again, if you don't shoot a lot, maybe not used to cleaning the gun.

Just thinking out loud, looking for easy targets.

PS, just me, but I would never spray a straight coat of retarder.
I avoid that stuff like the plague unless I absolutely need it.
And if I do pull it out, maybe a teaspoon mixed into a full coat of lacquer, at most.
 
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SC Relics Guitars

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Your gun either has a blockage, as mentioned above, or the lacquer is being applied too dry. The air to material ratio could be too high.

Disassemble your gun and leave it in a bucket of thinner for a little while. That should dissolve any paint caught inside the gun.

Do not spray retarder straight onto your body.


I'm still very much a novice, and will be forever because I don't build enough guitars to get very good at spraying, but I take advice well.

This is the wrong attitude to have. My advice is to put as much practice and effort into painting as you do into building. A bad paint finish on a good body will result in a bad looking guitar. You’ll find out all the little niggles and tips about spraying as you progress.

For the record, I use ANI R150 guns for laying down primer coats. It’s a great gun for that. But for clear coats I use a Devilbiss GTI pro lite with a 1.3 TE10 air cap. The results are amazing.
 

VertigoCycles

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Your gun either has a blockage, as mentioned above, or the lacquer is being applied too dry. The air to material ratio could be too high.

Disassemble your gun and leave it in a bucket of thinner for a little while. That should dissolve any paint caught inside the gun.

Do not spray retarder straight onto your body.

This is the wrong attitude to have. My advice is to put as much practice and effort into painting as you do into building. A bad paint finish on a good body will result in a bad looking guitar. You’ll find out all the little niggles and tips about spraying as you progress.

For the record, I use ANI R150 guns for laying down primer coats. It’s a great gun for that. But for clear coats I use a Devilbiss GTI pro lite with a 1.3 TE10 air cap. The results are amazing.

Right after I posted the question, I broke down the gun and soaked it in thinner. The tip was fouled with paint and I suspect that something was clogged. It makes sense that a clog would change the ratio in the middle of a short session, but I'd like to figure out why it clogged so I can attempt to prevent it.

FWIW, my comment about being a novice has more to do with my general ethos as a craftsperson. For example I'm near the top end of the curve TIG welding titanium, have been an instructor and people in my industry seek advice from me, but there's still room for me to improve my own skills...forever. I agree with your comment completely and believe me, I could never leave a poor paint job stand. I refinished the first guitar I built four times before finally getting a good result and while I'd like to get this on the first try for the sake of time, it'll take however much time it takes. Learning by failing is great, I'd just like to fail more quickly with this particular project so I can move on.
 

Preacher

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Right after I posted the question, I broke down the gun and soaked it in thinner. The tip was fouled with paint and I suspect that something was clogged. It makes sense that a clog would change the ratio in the middle of a short session, but I'd like to figure out why it clogged so I can attempt to prevent it.

FWIW, my comment about being a novice has more to do with my general ethos as a craftsperson. For example I'm near the top end of the curve TIG welding titanium, have been an instructor and people in my industry seek advice from me, but there's still room for me to improve my own skills...forever. I agree with your comment completely and believe me, I could never leave a poor paint job stand. I refinished the first guitar I built four times before finally getting a good result and while I'd like to get this on the first try for the sake of time, it'll take however much time it takes. Learning by failing is great, I'd just like to fail more quickly with this particular project so I can move on.

Dude, don't be too hard on yourself shooting Nitro. Much like welding there are a lot of variables that can affect the outcome.
Humidity, temperature and the mixing of the nitro/thinner and the like will affect the outcome.

In reference to your first question I was going to say it might be a clog where the amount of finish was not coming through. It can also have that same result if you spray when the temperature is really high, the finish dries before it hits the part.
I would say it is a lot like Welding, the longer you do it, the better you get at it.
 

KelvinS1965

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I weld MIG and have sprayed cars many times in the past, only recently got back into spraying a few guitars that I put together: It's a different technique on a small area like a guitar I found, as well as the fact they are wood and not metal makes a difference too of course in terms of prep and sealer, etc underneath.

I had a similar issue to you when spraying my last clear coats on a candy apple red Jaguar I did: Suddenly started throwing 'lumps' of beige splats that dried hard and I had to carefully wet sand off. I always flush the gun with thinners when I've finished/changing colour and take the needle out and clean the various parts. Even so I'd missed that this (cheap) gun had a kind of 'trap' that paint was getting stuck in, then going semi hard, only to come out mid spray.

I took it completely apart to clean and then the seals wouldn't work properly on it, so I ended up using a smaller 'touch up' type gun to finish off. Really annoying after getting back into the swing of spraying again and getting to know the adjustments the other gun needed for a good gloss from the gun. I don't plan on spraying any more guitars for a while, but if I do I'll choose a better one than the £25 one that did 3 bodies and 2 necks before the seals went...it's annoying also because I've got a really good 'Devilbis' spray gun that I've sprayed about 25 cars with over the years, but I've lost some parts for it and you can't get spares because it's the old type of gun that aren't sold these days due to excess paint/VOC issues.

Maybe you could come and do some welding for me as I'm out of practice and I'll spray for you now I'm back in practice. ;)
 

VertigoCycles

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I weld MIG and have sprayed cars many times in the past, only recently got back into spraying a few guitars that I put together: It's a different technique on a small area like a guitar I found, as well as the fact they are wood and not metal makes a difference too of course in terms of prep and sealer, etc underneath.

I had a similar issue to you when spraying my last clear coats on a candy apple red Jaguar I did: Suddenly started throwing 'lumps' of beige splats that dried hard and I had to carefully wet sand off. I always flush the gun with thinners when I've finished/changing colour and take the needle out and clean the various parts. Even so I'd missed that this (cheap) gun had a kind of 'trap' that paint was getting stuck in, then going semi hard, only to come out mid spray.

I took it completely apart to clean and then the seals wouldn't work properly on it, so I ended up using a smaller 'touch up' type gun to finish off. Really annoying after getting back into the swing of spraying again and getting to know the adjustments the other gun needed for a good gloss from the gun. I don't plan on spraying any more guitars for a while, but if I do I'll choose a better one than the £25 one that did 3 bodies and 2 necks before the seals went...it's annoying also because I've got a really good 'Devilbis' spray gun that I've sprayed about 25 cars with over the years, but I've lost some parts for it and you can't get spares because it's the old type of gun that aren't sold these days due to excess paint/VOC issues.

Maybe you could come and do some welding for me as I'm out of practice and I'll spray for you now I'm back in practice. ;)

If I was anywhere near you, I'd take that trade.
 

VertigoCycles

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to follow up, after the soaking of the tip parts yesterday, I've been able to get on a couple of color coats today and it's laying down pretty nicely. I did add just a little bit of retarder but this mornings coat was dry enough after just a few hours to sand a bit (the powder that sprayed yesterday didn't fully melt, so I sanded it lightly with 400 just to flatten it out) and powdered surprisingly well. I've got a couple of small runs I need to clean up, but it'll be ready for clear soon.

Another surprise that I'm not wholly against is that it started checking after a few hours. Humidity is 57% today.
 

VertigoCycles

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I sprayed another base coat this morning because there were a few spots that were a little too thin. Posting this photo to show the level of cracking in the lacquer. This seems a bit beyond the micro checking that I've seen and there's clearly something going on that I don't understand.

45E931C6-2FF9-4E0C-8AFA-7FAC6FF29921_1_105_c by Sean Chaney, on Flickr

I'm going to leave this alone until tomorrow to see how far it progresses but the "checking" is pretty big with the biggest one near the bevel being about half a millimeter wide. You can see that I sprayed over top of the checking that happened yesterday. I need to make a decision to sand it back and start over or see what happens when I start adding clear. I'm not against the typical relic look but I'm also not doing anything to intentionally make it happen.

Again, the schedule is this

Cardinal Sanding Sealer - 2 coats
Cardinal gloss with 10-15% of Vivitone white pigment, 4 drops of red Trans Tint, maybe 10% thinner and 5% retarder - 4 coats total

I very lightly sanded off the powder that had gone on earlier and the subsequent coats have gone on quite nicely with minimal orange peel. I got a small run or two and they were lightly sanded back before another coat followed.

The whole system is kept in my garage which is within a few degrees of the outside temperature. It was sprayed outside, in the shade and then moved back into the garage to dry...this isn't a result of a temp swing or it being in the sun.

Any advice or shared experience is very welcome
 

Drak

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A few things:
The 'checking' I'm reasonably sure is some sort of an adhesion problem between the lacquer and the substrate, whatever that is.
Or it's shrinking like mad, which I've never seen happen in front of me.
Lacquer doesn't check like that unless you force it to, that is completely abnormal.
I have guitars I sprayed 25 years ago with the finish still in perfect condition.

Humidity:
I find it more effective to go by dewpoint, or what's known as the '20 degree dewpoint' rule.
If the dewpoint is within 20 degrees of the ambient temp, time for the retarder.
Example: Ambient temp is 85 degrees, dewpoint is 65 degrees, you're right on the knife's edge.
Dewpoint 60, totally safe, 25 degree difference, rock on with no worries and no retarder.
Dewpoint 70, definitely time for a teaspoon of retarder, only 15 degree difference.
That's a much more accurate and definitive method.
Just look up your local weather, mine updates every 15 minutes.

And so if you're outside the 20 degree barrier, you're completely safe, retarder is just not needed at all.
A regular coat of lacquer will re-dissolve a dry coat underneath it, usually no problem.
Using retarder is a crutch you really don't want to get in the habit of leaning on.
Only when absolutely necessary and small amounts even then.

Spraying over cracks: Paint doesn't fill cracks, depressions, or much of anything else.

If it's cracking like that in less than a day, I'd be concerned about the longevity of the finish.
As in, I think there is an adhesion issue, and you could wind up losing hunks or chunks of finish due to a poor adhesion to the substrate.

For all the time it takes to build a guitar, for me, when you get this close to the finish line, there's no room for fudging things.
With evidence of those cracks, I'd be sanding it all off w/o thinking twice about it.
Unless, as you said, you like it that way.
 

eallen

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You mentioned a key, you have a couple runs. That tells me you may be trying to put your color coats on as a full gloss coat. Nitro shouldn't go on anywhere near the ability to run except maybe the last couple clear coats. Another tip early on. was that you were concerned it was going on top dry.

Color coats should be light coats until covered & not covering in a single pass. That comes to your checking problems. My guess is you have put on too heavy coats too fast & the solvents are having to find a way out resulting in "checking". Whatever you sealed with under you color could cause it as well.

Eric
 

VertigoCycles

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thanks all! good advice in here and I appreciate it. I've started sanding it all down to wood and will have another go at it this week.
 

old wrench

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I usually spray either clear lacquer or tinted lacquer, so I don't have a lot of experience with using pigments, but 10% or 15% pigment sure sounds like a lot.

Looking at your pic in post #11, I wonder if that high percentage of pigment plus too heavy of a coat might be causing your problems with the finish cracking?

Lacquer dries quickly.

Pigment, at least the ones I've used - not so quickly.

Could be that the surface is drying quickly - like you'd normally expect with lacquer, but the pigment rich blend underneath is drying a lot slower - leading to the cracks in the surface.

.
 

jrblue

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My guess is you have put on too heavy coats too fast & the solvents are having to find a way out resulting in "checking".
This would be my guess. I think you need to strip down to bare wood and re-do the whole finish, checking your formulation and sticking to really thin coats with sufficient dry time between.
 

Sea Devil

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Any cracks like that need to be removed, no matter what the cause. They can't be fixed by adding more paint, only by removing it. It doesn't always need to be all the way down to the wood, just below the level of the crack, but taking it down to the wood is still a good idea.
 

VertigoCycles

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I took it down to the wood and will be sealing it today. Weather here is bonkers for the next week so it'll be slow going but I might be able to spray in the mornings. I've added double the amount of uncut clear to my mixing jar and will thin it a bit in the gun before I shoot and will be sure to shoot much thinner coats.
 

Sea Devil

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Probably a good idea. In my early experiments with lacquer, I found that too much tinting agent/pigment, especially Mixol, led to horrible, unpredictable results -- from powdery, cracked surfaces to gummy, "Nev-R-Dri" color coats.
 




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