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Airbrushing Things
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10102&t=1544		 Page 1 of 1
Author:  Sprockett [ Fri Apr 01, 2005 2:44 pm ]
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Just wanted to share some new ideas with the gang, I'm in a rush to apply the finish on a guitar this weekend so I can let it cure and get it ready for a class this month.

Because I'm rushing I accidently just slightly sanded through the epoxy on the back of the headstock enough to just change the color under the lacquer, because this is pale mahogany I really didn't notice until I had a number of coats of KTM on. Well it was driving me nuts so here's what I did (you could only see it from a distance but it was there):

I pulled out my pasche airbrush and mixed up some KTM in a bottle with 1 drop of tobacco stain from SM, I set that up and then using a very very fine spray feathered the light area in. There was one other spot right at the end of the headstock and I feathered that as well. Because I used such a fine coat after I was done you can't see it unless you look really hard, and the tobacco though not matching exactly colors it just enough that it fools your eye which is all I wanted.

You can do the same thing to even areas out or cover up highlites, I have even fixed a rosette's inlay using an airbrush and some water colors lightly applied and then laquered over. On the flag guitar there was a spot that lost it's color so I just sprayed some color back in, I can't even find the spot now!!

I would post pics but there's nothing to see now, the next time it happens though I'll do some pics so you can see...

-Paul-
Author:  npalen [ Sun Apr 03, 2005 10:00 am ]
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Paul--I'm a novice with the airbrush. Do you find that thinning to a much lower viscosity is required than with conventional spraying?
I find the airbrush quite a handy tool even with limited experience but am still on the steep part of the learning curve.
Also wondering about the pros/cons of conventional suction feed compared to gravity feed. Seems like gravity feed wouldn't require as much thinning?
Thanks
Nelson
Author:  Sprockett [ Sun Apr 03, 2005 12:31 pm ]
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Nelson...

You don't need to thin it too much, this was almost straight out of the can with just a little alcohol added, what your after is not if it will get sucked into the gun, you want it thin enough to properly atomize.

Before I built guitars I build RC Gliders, trains, models and lots of RC cars so I've had a bit of practice with the airbrush, I can't do stuff like Mario can but I'm pretty handy with it.

The model I have can convert from a suction to a gravity feed, for this I used the suction because 1 drop of tobacco stain is powerful stuff so I mixed in a small paint jar for the sprayer. Normally though for touch ups or just adding extra color I'll use the gravity cup.
Author:  Dave-SKG [ Mon Apr 04, 2005 6:04 am ]
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Hi Sprockett,
Just wondering there are afew places on the Heart/Richards guitar that probably could use some touch up. Do think it would blend well using an airbrush ( ihave been thinking about it) with this type finish? This isn't a joke...I really do need your input if you are willing to give it. Anyone elses thoughts too. Thanks!
Author:  Michael Dale Payne [ Mon Apr 04, 2005 6:08 am ]
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Paul I finished an entire guitar with KTM-9 and a airbrush last year. Came out good, took a bit longer and I got orange peel while spraying so I had more leveling to do. I was a bit scared of thinning the KTM-9 too much but I have done it on some of my wifes custom jewel boxes she built very recently. It is very convenient for small projects.
Author:  npalen [ Mon Apr 04, 2005 6:57 am ]
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Paul--My problem is not being able to suck it into the gun. Can't atomize it if I can't suck it.
I suspect that I'm using too fine of a needle on my Pasche.
Nelson
Author:  Chas Freeborn [ Mon Apr 04, 2005 7:23 am ]
Post subject: 
I have used this technique for years on furniture where I've sanded
through usually the edges of stained pieces during the sealer phase. It
does work, but beware that the stain will "age" differently when it's
suspended in the clear coat than it does when absorbed by the wood. I've
seen pieces a few years later and the repaired areas had become more
visible. This is most evident with stains having a significant red tint to
them.
My favorite gun for this is a DeVilibis touch up gun (Model EGA-502:
probably illegal in CA by now). I can throttle it down to not much larger of
a pattern than your Pasche, yet it can handle heavier liquids, therefore
requiring less thinning for it to siphon smoothly.
-C
Author:  Colin S [ Mon Apr 04, 2005 7:44 pm ]
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I've also airbrushed a whole guitar, in fact if I move back from french polishing to water born or nitro then I think I will again use an airbrush. It takes time but with the airbrush you can lay down multiple very fine layers in an almost continuous spray with no chance of a run. It also can produce that wonderful satin sheen, that I really prefer, and most or all of the cutting back and buffing out is eliminated. A very light fine grit sanding before the final session was all that was needed. The advantages to me are that the wood ends up looking like wood rather than plastic with a pattern that some of the high gloss finishes can produce, and the thickness of the finish is very thin, but retouching if it's damaged are dead easy.

Colin
Author:  Mattia Valente [ Mon Apr 04, 2005 11:07 pm ]
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FWIW, a small, finely controllable gun like the SATA MiniJet is ideal for guitars. You can use the regular nozzle for round or flat (my preference) spray, the atomization is very fine indeed, and controls of flow rate, shape, airflow are dead simple. You can even get an airbrush kit to go with it if you want to do finer details, or an SR tip (spot repair) for small areas. Plus it's HVLP, so what you do spray mostly gets on the guitar, and not floating all over the place. I've found it to be a really great all-rounder for guitar spraying. Finish thickness and film depends on application technique and familiarity with your gun more than anything else, I think. I just finished my third guitar with this gun (electric, sprayed clear and colour coats of Target USL), and now that I've dialed in the flow and pressure settings I like, I can do anything from a very light mist coat (1 brisk pass) to a full 'wet' coat (3 brisk passes; USL runs quicker than Niro, in my experience).
Author:  npalen [ Tue Apr 05, 2005 4:47 am ]
Post subject: 
Mattia--Do you know of a source here in the States for the airbrush kit and SR tip for the minijet?
Thanks
Nelson
Author:  Mattia Valente [ Tue Apr 05, 2005 6:50 am ]
Post subject: 
Not off-hand, but I think any one of the many SATA dealers should be able to sell you the tip or the airbrush kit pretty easily. A lot of the guns many people are pushing are 'SR' ones anyway. That includes (for example) spraygunworld.com, off the top of my head. I was confused about the different nozzles, so I gave SATA a call, and their tech department reccomended the regular 1.0mm tip for most lacquers (water based or nitro). The airbrush kit is also called a 'Design Kit' or similar, and comes with an additional tip and about 5 different cups. SATA's website calls it the 'DECOR KIT', order number 125773 (that's the German version, though)

OTOH, a cheap airbrush will probably cost less, given, Sata's not insgnificant prices, which seem to have gone up since last I checked (probably the weaker dollar finally working it's way through to the retail market on your end..) They've also come out with the MiniJet 4. Maybe I should go buy a replacement cup for the 3 I've got before they stop making them altogether (new one has a 'one-click' mounting system or somesuch...)
Author:  Sprockett [ Tue Apr 05, 2005 7:24 am ]
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Hmmmm I'll have to do some shopping, are you using a standard compressor to power it Mattia??, I was thinking of going with a turbinaire HVLP setup but it's really expensive.

I know some people like Mike Doolin use a little cheap touch-up gun and get really good results, but I find the finishing process easier if I have better tools. Right now I'm using a Devilbiss HVLP gun and it works but it's a little fussy sometimes, I think it's partly because of the air supply but a smaller gun would be better.

Time to go digging...

-Paul-
Author:  Mattia Valente [ Tue Apr 05, 2005 7:33 am ]
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Yes, bog-standard, not even all that high CFM compressor I bought years ago. The gun's worth more than the compressor, by a good bit! It's a 1.5hp oilless, got a large (50 liter) tank on it, but can't deliver huge CFM. Too little, on paper, to run any full-sized HVLP conversion gun. This said, if I top up the tank, I can do about 1 full coat (3 passes over each surface) before the motor kicks in again to get the pressure up to par.

If you've got a compressor, MiniJets can be had from around 210 dollars (looking at a few hits googling for 'SATA MiniJet'). I really like the gun, and the vast majority of other users I've heard from agree. One or two people on the MIMF said they couldn't get used to the feel, but to me it feels like a very smooth, well-crafted, small, sits-in-your-hand gravity feed gun. Nothing unusual, the trigger and dial are all in logical places, and it works a charm.

I still want to upgrade to a proper regulator/micrometer and a better air filtration system, but even without those things, even 'eyeballing' the pressure on the compressor's built in guage, I'm getting nice, consistent results. The price tag's not low, but you are arguably buying the best gun on the market. The only thing I'd consider upgrading to, at this point, would be a Fuji system, but frankly I can't really see the point.
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