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Practicing your spraying technique
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=26324		 Page 1 of 1
Author:  James Orr [ Tue Mar 02, 2010 3:34 pm ]
Post subject:  Practicing your spraying technique
A year ago I picked up an Iwata conversion gun, compressor, regulator, and filter under the impression that I'd automatically be capable of producing a good finish. In other words, it's the equipment, not me :) Boy was I wrong . . .

This year, now that we're in a house, I don't have to be as mindful to the noise of the compressor and would like to spend some time practicing and honing the technique. My only real question is this: what do I spray?

Would you spray MDF? Finish grade ply? Cardboard? What?
Author:  Dave Stewart [ Tue Mar 02, 2010 3:49 pm ]
Post subject:  Re: Practicing your spraying technique
Hi James, what are you trying to see? I keep a piece of cardboard inside my booth to confirm my settings, pattern and gun performance quickly before each coat. (I just use a fairly cheap touch up gun). If I'm spraying colour, I'll substitute a white box so I can see what's going to happen on the guitar. Dan MacRostie advocates when everything's set, you spray each step on a sample board first before going to the guitar. It allows corrections and at the end, you have a sample of the exact finish.
Author:  bluescreek [ Tue Mar 02, 2010 3:55 pm ]
Post subject:  Re: Practicing your spraying technique
I used cardboard , and 1/4 ply
Author:  James Orr [ Tue Mar 02, 2010 4:20 pm ]
Post subject:  Re: Practicing your spraying technique
Thanks guys

We're supposed to spray wet. I want to see what wet means, what too wet means, and what too dry means.

I also just want to practice so that the finish is as fine as can be off the gun.
Author:  TonyKarol [ Tue Mar 02, 2010 5:32 pm ]
Post subject:  Re: Practicing your spraying technique
anything sanded to 220 will do just fine ...

you will want ot play around with the gun settings, the air pressure, and the fluid viscosity, to see what your gun will like to spray, and with what conditions ...

thinner material may work well with lower air settings, but thicker wil wnat more air to atomize it ...

what size is the guns needle ??? this will dtermine a lot about the viscosity .. thicker material just wont flow/atomize out a small orifice ...

my sata minijet 4 will run nicely at about 20 psi .. with slightly thinned material .. if the viscosity is off, you see it right away in the spray pattern, as it doesnt flow out as nice ...

wet .. the finish should look wet and shiny as you lay it down .. dry will be pebbly looking, almost satin .. too wet/heavy - it will run/drip within seconds ...

its all about moving the gun at the same rate and distance from the piece being finished .. that gices the right mapount of finish, and an even coat ... and every gun works slightly differently, it takes a few tries to get everything down ..
Author:  Fred Tellier [ Tue Mar 02, 2010 5:51 pm ]
Post subject:  Re: Practicing your spraying technique
Take a dark colored piece of poster board and paint it, get used to the gun settings, you will waste some finishing product but it is easier than sanding it off an instrument. Too wet will sag, open the gun to the point you make a sag so you see what causes the sag, too dry will look rough and pebbled looking and will not show a wet shiny look behind the fan pattern as the gun moves along. Play with the fan pattern adjustments until you get comfortable what they do and how much the pattern changes with each adjustment. If you are using Nitro lacquer it is almost idiot proof and is easy to learn to spray as sags are easy to sand out, the products that don't burn into previous coats are harder to do well and may need more practice.

If you are spraying other products read up on the application of it, the amount of reducer needed etc. you could even pop into a body shop and see if one of the sprayers could help you get started. On the 1st 7 guitars I lacquered I used a $20.00 Chinese HVLP touch up gun and my finishes are as good or better than any factory guitar, any flaws are in the fits and filling of the wood not the spray and buffing results.

I wish I could afford a high end gun, I have survived this far with the cheap gun but the needle packing is shot and parts are not available for these cheap guns. My next will be more expensive with the requirement being the availability of spare parts.

Fred
Author:  Robert Renick [ Tue Mar 02, 2010 7:11 pm ]
Post subject:  Re: Practicing your spraying technique
Years ago I purchased a fancy Binks Mack sl gun, after a week of frustration I brought it back to where I bought it. It was a spray shop that dealt in all types of guns. Fortunately they had a booth and a tech to give me the tips to make it work. Point being getting it right takes a bit to understand how the variables relate: pressure, tip adjustment, and material thickness and fan width, distance from the gun to the work, hand speed, and some guns can regulate material flow as well. That is a lot of variables to adjust.

I keep a roll of the green masking paper from the paint supply shops in the spray area so I can test the spray and pull down and rip off to get fresh paper. I can see the fan and the level of mist clearly on the green. Wood needs to be sanded properly to really show be meaningful practice.

Fred, it is great to have the spare parts, I keep a complete rebuild kit on hand with extra needle packings. Once you get it down though, you can spray pretty well with a cheapo gun too.
Author:  Daniel Minard [ Thu Mar 04, 2010 1:28 am ]
Post subject:  Re: Practicing your spraying technique
Before you start spraying finish, spray filtered water on the cardboard. (don't put anything in your gun without filtering it first) Practise with distance from the workpiece, speed of travel & gun settings. Try to get a 50% overlap on each pass & practise releasing the trigger after every pass & pulling again before the spray hits the board, going the other direction.
Get a strong light glancing across the work so you can see the shine clearly.
You can learn a lot with water, even though the viscosity is much lower than any finish you will spray.
Just make sure you dry the gun out well when you're done & spray some thinners through to make sure the water is purged.
Try to move your whole body back & forth, rather than working from your elbow or shoulder. This will help maintain a constant distance between the gun & your work.
And... Have fun! (I love watching the finish lay down all smooth & shiny.)
Dan
Author:  Mike Loukakis [ Thu Mar 04, 2010 2:16 am ]
Post subject:  Re: Practicing your spraying technique
I would also suggest to make a mock-up of the cutaway side area (from any material like hardboard in a U shape) and try to spray in there. It is fun to spray in a tight area and having the finish lay down nice with no runs or orange peel. You'll have to deal with the overspray hitting the opposite area (if it is a tight cutaway like on an archtop or electric guitar). The corner of the heel and side is also a similar situation (on a spanish heel where you spray neck and body assembled)Also slots in a piece of thick ply is nice for practicing spraying headstock slots and laying down a perfect finish that needs no sanding or buffing. Those are difficult to sand and buff. You should file the ramps on one end of the slots.
I made those mock-ups for myself and practice every time I get to use the spray gun.
Have fun!!
Author:  James Orr [ Thu Mar 04, 2010 11:59 am ]
Post subject:  Re: Practicing your spraying technique
Awesome advice, guys!
Author:  David LaPlante [ Thu Mar 04, 2010 12:06 pm ]
Post subject:  Re: Practicing your spraying technique
Recently I tested my flatting agent mix on a large sheet of Plexiglass (the cheap thin stuff from Lowe's) showed every flaw and perfect I think for testing your technique and the "wetness" of what you are laying down.
Author:  gozierdt [ Thu Mar 04, 2010 1:40 pm ]
Post subject:  Re: Practicing your spraying technique
I would second Mike's advice. Once you have the basics of spraying on a flat
surface (I usually use cardboard, especially unprinted cardboard, where the color
change gives you a good indication of how wet and how uniform the spray cone
is), I would make a mock-up of the bent sides of a guitar and/or cutaway, and
practice on that. The trick is to keep the nozzle at a very uniform distance from
the surface being sprayed. For a concave surface, that usually means you
have to do a lot of twisting the wrist, along with moving forward or back to keep
the nozzle to surface distance as uniform as possible. You also have to learn to vary
how fast you rotate the gun- it's very easy to get too heavy a coat on a concave
surface like the waist or cut-away. Don't get discouraged though, it's like riding a
bike- once you figure it out, it's very natural from there on. I find the most tricky
part now is getting the viscosity of the material correct. I'm starting to use Zahn
cups (little cups with a hole in the bottom- you measure how long it takes the cup
to empty as a direct measure of viscosity) to try and keep the material viscosity
the same from one guitar to the next.
Author:  gozierdt [ Thu Mar 04, 2010 1:41 pm ]
Post subject:  Re: Practicing your spraying technique
I would second Mike's advice. Once you have the basics of spraying on a flat
surface (I usually use cardboard, especially unprinted cardboard, where the color
change gives you a good indication of how wet and how uniform the spray cone
is), I would make a mock-up of the bent sides of a guitar and/or cutaway, and
practice on that. The trick is to keep the nozzle at a very uniform distance from
the surface being sprayed. For a concave surface, that usually means you
have to do a lot of twisting the wrist, along with moving forward or back to keep
the nozzle to surface distance as uniform as possible. You also have to learn to vary
how fast you rotate the gun- it's very easy to get too heavy a coat on a concave
surface like the waist or cut-away. Don't get discouraged though, it's like riding a
bike- once you figure it out, it's very natural from there on. I find the most tricky
part now is getting the viscosity of the material correct. I'm starting to use Zahn
cups (little cups with a hole in the bottom- you measure how long it takes the cup
to empty as a direct measure of viscosity) to try and keep the material viscosity
the same from one guitar to the next.
Author:  mateo4x4 [ Fri Mar 05, 2010 12:18 am ]
Post subject:  Re: Practicing your spraying technique
James Orr wrote:
Thanks guys

We're supposed to spray wet. I want to see what wet means, what too wet means, and what too dry means.

I also just want to practice so that the finish is as fine as can be off the gun.



If you are near the portland oregon area, I would be happy to supply some unfinished projects that could use a few coats of...well, anything. LOL

-Matthew
Author:  Daniel Minard [ Fri Mar 05, 2010 1:13 am ]
Post subject:  Re: Practicing your spraying technique
I find it easiest to spray inside the cutaway by spraying across the side, not along the grain.
Too easy to bump into the heel or the cutaway horn... Or get a run on the ends of the pass.
Keep the gun moving & pull the trigger in short bursts when working in tight places.
More important to keep a good light working across the finish when you are in a tight spot. If you can't see how wet the surface is, you're gonna get dry spots or runs... Or both.
Just what works for me...
Author:  Danny R. Little [ Fri Mar 05, 2010 3:38 pm ]
Post subject:  Re: Practicing your spraying technique
I just bought a turbine and for practice I painted my father's basement. Boring, but I got to know the gun and cure some performance anxiety.

Danny R. Little
Author:  Ken C [ Fri Mar 12, 2010 9:18 pm ]
Post subject:  Re: Practicing your spraying technique
James, if you are going to practice your spraying, I'd practice on something other than just bare wood. Spraying a surface that is already nice and smooth will be a lot different than spraying a surface that soaks up the finish. I would shoot your first three or four coats, then level the finish with 320 or 400 grit paper to get you a nice level surface. You can then use this piece to give you some practice getting a finish wet enough to lay flat while not being so wet to sag or run. I'd make your practice piece big enough that you will have the ability to play with your gun settings after a pass or two.

Ken
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