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Hey old friends...long time no see I recently decided to offer nitro as a back and sides option for my guitars and in the end ordered a Fuji minimite 4 system with the gravity gun (standard 1.3mm). I think several folks here have these and was wondering if anyone could recommend a schedule and perhaps some tips...

The laquer I have (the only one available here) is not pure nitro, but it also has some alkyd and acrylic bits added, unfortunately they do not say how much. It is different from the nitro I know from the past (as a kid I used to steal some from my dads shop and paint wooden toys) as it has less of that characteristic stench. After it it dries for a couple hours it seems not to smell at all.

For spraying they recommend 5-10% dilution for 20 seconds viscosity through 4mm hole. For my brushed samples I tried up to 40% thinner and seems OK. The spray system should be here on Monday.


Thanks!

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Probably the best tip I have is to change the tip to a 1.0. BUT, I spray smaller instruments.

Also, you have to really crank the tip tight.

With the minimite 4 system you may well be fine with the 1.3mm tip, I'd try some tests with it first before paying for a new tip.
Especially with an "mystery" lacquer.
I take it they recommend their own thinners/solvent for dilution?
I spray (minimite 3) using waterbased (Enduro-var) and 1mm tip gives better results, but very difficult to give any tips with an unknown quantity.
Most useful guide I've seen to spraying guitars is here http://howardguitars.blogspot.co.uk/2015/05/spray-finish-problem-solving-chart_18.html
Good general guide to laquers here http://howardguitars.blogspot.co.uk/2015/02/air-dry-lacquers.html
Just test until you see how it goes is the best I can offer.
Hope it's of some help.
Let us know how it goes, I'm sure you'll love the Fuji system.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Hey Colin those two sites are really useful. I am a novice sprayer and am still trying to get to grips with the technique.

I bought the Fuji three stage turbine but wished I had bought the silenced one. It is seriously noisy. I am pretty sure it is good machine but there is a lot learning to get good with it.

Dave

I lucked out and bought a once used Q3 from ebay.
Don't need the earplugs so much.
Yes, Brian has been generous with information on his blog.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Honestly I think hordes of general advice can be provided but, at the end of the day, the material you are spraying, the conditions (humidity, temp, ...) come significantly into play, along with how you adjust and test. You'll need to play with it. The good news with lacquer (even with mystery, hopefully) is that it is very compliant and sandable.

The one thing I might caution is not on the spray side but on the finishing side. Curing time is key to getting a hard enough surface to not go mad chasing scratches, et cetera. The Fuji system is excellent, though. Good luck!

Andy

Andy you are dead right. It seems to really be one of those skills that has to acquired by doing. As a rather slow amateur builder this is a bit of a bugger since it is so long between spraying sessions that I tend to have forgotten what I learned last time!

Still your point about being able to sand out and correct spraying errors is true and encouraging.

Dave

Thanks guys. Got it today and so far I hate it with every single cell and fiber of my being. The smell, the noise, the mask, the clouds of poop killing the flowers, bees and birds in my yard. What the hell was I thinking. As for the actual spraying, if I get enough paint in to get a wet coat, it either runs or ends up super thick and slow to dry. If I close the needle in, the layer will be dry and dull drying to a sandpaper texture. I'll have to learn how to use it and finish what i started, only then smash it with a hammer and return to french polishing.

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It's the nitro, and the learning curve - not the gun.
Thought about trying water based?
Pros - Can be pretty tough, this first one was sprayed in my workshop, no booth (although I use one now,and can do without a mask), don't need an explosion proof fan, little smell, not too hard on the environment. Very forgiving, and sanded and buffed out after 7 days drying. easy to spray.
Cons - Has a slight amber tint (which I actually like), bit expensive in E.U.

Black walnut.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Yes I should try water based too before smashing it As for the nitro, this is the best i can do so far, although I did not finish exploring all knob combinations. Also made a big mess on the side. I had a massive run which I decided to scrape level when it seemed to have dried some. What happened is that a large area just peeled off. When I re-shot it turned very dark, meaning the shellac seal was gone. I'll have to strip it again now.

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FWIW, I recently got some spraying and setup advice from a guy who paints cars for a living. This is the way he taught me to set the fluid level. I use an Iwata LVLP conversion gun, but the advice should be the same.

After setting the fan size (I like 5" or so), make a hang loose sign with your hand. Touch your pinky to your test surface and thumb to tip of your gun. That's your distance. Open the fluid nozzle all the way. Hold the gun still and spray for three seconds. If you get runs, close it a quarter turn and repeat in a fresh spot. Continue until you're not getting a run. That's your fluid setting.

Others might set up their guns differently, but that worked well for me. I don't know how turbines work. I'm assuming your air is your air, and it's not adjustable.

Alaxandru believe me I have been there so often. My orange peel can beat yours any day! It sometimes feels like I have removed more coats than I have put on!

However it does get a bit better each time. I don't so often get runs and my orange peel is not quite so deep and does get sorted with sanding. I use wet and dry paper then micromesh abrasives and don't do any buffibg/polishing and do end up with a good finish

The reason I have persevered is that nitrocellulose gives such a tough, long lasting finish. A guitar is something you are handling and fingering constantly you really don't want to have to worry too much about damage to the finish.

This was my last go at it and I was pretty pleased:

Thanks guys. I am not really worried about the amount of sanding, nitro seems super easy to level. I got a mirror surface from a really horrible brushed job (5 coats) but I kind of hoped for a smoother result from spraying. Oh well.

What really bugs me now is how easy it is to peel of. If I start poking at it from a ran/thick spot, I could just pull (or scrub) everything off. If tomorrow it does the same I might take off everything and spray again on the bare wood, no shellac coats.

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If it's peeling off its not your gun. Unless your gun is dirty.

You're laying it on thick. Many variables as to why, so you have to figure out what you're doing and address it. Let me rephrase that - your finish is being applied thick. You laying it on is a variable, not the result.

Take this with a grain - I learned to spray conventional, and naturally gravitated to conversion HVLP. Switching to the Fuji system from a Sata gun seemed like going backwards from an adjustable control perspective - you can't adjust the air from the turbine on any system less than a Q5.

However, the Fuji is very forgiving with adjusting the air from the hose, meaning, I turn it down "about 1/2 way" and adjust the spray and fan from there. Or, variations thereof. Doesn't take long, but, I know what I'm looking for when I spray. That being said, you can adjust the gun with full air, but with a 1.3 tip, it lays down a LOT of material, sort of negating the product savings with an HVLP system. If you're fogging your spray area (and material is on the ground), you have a few adjustments to make.

Aaron, just curious, but does fogging the area indicate any type of adjustment more than others?

Thanks. What is easily peeling off as a whole sheet is a test guitar where indeed, I have sprayed a lot on (sorry but I can't figure out anything from carboard and so on)

But the "good" guitar where I did not spray a ton seems to have a problem too. I found an air bubble on the binding. I poked it with my nail and from there it started to chip. I feel I can easily chip it all off starting from smth like this.

__

Yes if I leave the hose full open it fogs the entire neighborhood

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Could be any number of things, depending on who's spraying, and what you're using to spray. For this, I'll call it overspray.
Conventional spray guns - comes with the territory.
Conversion HVLP - way less
HVLP turbine - relatively non-existent.

For that scenario, high pressure is a variable.

Bottom line for me, if it's going in the air, then it's all waste. THE key benefit for me is putting the finish product on the surface. If it goes on the ground, something's wrong. If that happened out of MY Fuji, first thing I'd do is take down the pressure and material, and readjust the fan, assuming the mix is where I want it to be (and my technique is in check).

You might work on some test panels, rather than using the guitar as the guinea pig. That may help lower the frustration factor. Best of luck.

Andy

+1!

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I too would recommend dialing in your spray technique on a test panel. Check your material viscosity and maybe start
with a very low air setting and work your way up to where the material flows nice a good. You'll get it. Maybe thin your
nitro a bit for your test panels until you get the hang of it. Btw, as to the peeling, your shellac was dewaxed?? Nitro is
probably the easiest coating to spray:) imo.
Ken

I do have a large spruce test panel, a test guitar (a shop prototype) and a "real" guitar. The spruce panel didn't teach me anything as it reacts very differently than the rosewood.

The shellac used for porefill and seal is buttonlac which i dewaxed myself with coffee filters. Perhaps chemically-dewaxed shellec is needed, but my current feel is that shellac has no place under nitro.

This morning I decided to peel the entire guitar, with the following results: adhesion on the back, less than 5%. Film thickness 8 mils. After peeling the wood looked exactly as before shooting, I could even see some of the vertical shellac rag marks. On the sides there were a few areas were it was well bonded. Perhaps the wood has been rougher there, or I sanded the seal coat, I don't know. There was one area I peeled, sanded and recoated (no new shellac) in the first day and that part bonded the best. So I think i will sand it down well and restart with no shellac at all.

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I like to shoot a vinyl sealer before I shoot lacquer. But that said, I am suspicious of your shellac. I have no issue (and have never had issue) with shellac wash coats under lacquer. In fact my spruce tops are typically washed in a few coats of dewaxed shellac as a matter of protection. YMMV but I'm wondering how dewaxed your shellac may have been.

That said this becomes an issue of specific chemicals being used. Do you know anyone else using the lacquer product, as you are? Being in the USA, our choices are common which means it is easy to ask 20 other people what their experience has been. That may be part of the issue here, is that this feels like process and chemical R&D?

You could take a test panel, coat half of it with your shellac, leave the other half bare wood. Shoot and then see if they behave differently once cured.

Andy

Another local builder uses it with very good looking results, but no shellac, he shoots it over epoxy. I wonder how commercial dewaxed is made. Mine was through a coffee filter, it makes it plenty clear for FP purposes but...

The difference in adhesion is quite obvious, see the 2 pics. From shellac the film peels like a dossier cover. It took me under 1 minute to pop it off the entire back. Where it was stuck, you could hear a breaking/crackling noise (same as when cleaning a hard glue), the film fractures and chips as it comes off the wood and quite often it also rips the pore fill.

So for try number 2, I cleaned the guitar well, made sure all shellac was sanded off and then brushed on the first coat, really working it in.

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I filled the guitar I just finished with Z-poxy on the back and sides, sealed with kusmi buttonlac that I dewaxed through a coffee filter (twice), and shot with Cardinal lacquer. Adhesion was excellent.

I'm really sorry you're having such a crummy time finishing. The guitar I described is koa and redwood. I wonder if there's an issue with the rosewood itself not interacting well with the shellac?

Kusmi here as well, but I only ran it once. This stuff is super waxy, will filter it twice and do a test.

I guess any finish can be crummy when you learn it. Right now I am seeing the light I think. After 4 sessions (heavily sanded with 240 before each) the leftover pores seem all filled. Will wait 1 week, do a hard leveling and hope no sand through.

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