Official Luthiers Forum!
http://www.luthiersforum.com/forum/

Finishing procedure
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=31589		 Page 1 of 1
Author:  Sondre [ Thu Mar 24, 2011 9:33 am ]
Post subject:  Finishing procedure
Hello folks,

Would you guys care to share some details on your finishing procedure? (I will be spraying nitro)

For example, do you sand between every coat? Which grit do you use between the coats, and which grits on the final coat before buffing? Which buffing compound(s) do you use? How many coats do you typically end up with, etc, etc...

Thank you!
Sondre
Author:  alan stassforth [ Thu Mar 24, 2011 10:55 am ]
Post subject:  Re: Finishing procedure
Depends on the wood.
There should be TONS of info in the archives here.
Good luck!
Sand to 220.
Spray, spray, sand 320, spray, spray spray, sand 320,
etc., until it's covered.
Wait a month, sand with wet 600, or 400 if bad spray job,
then start with polishing compounds that you like.
I end up with some meguiars compund, and prefer the "not" buffed look.
Todd stock says to wipe after every sanding with naptha.
Very good advise.
This will work with nitro, not all finishes,
and I won't get into the filling stage. gaah
Author:  Lars Stahl [ Thu Mar 24, 2011 12:18 pm ]
Post subject:  Re: Finishing procedure
also depends on the thickness you have achived of when you sand first time .many spray 5 times to build a safe layer that can then be sanded down to flat. I spray 21-3 times then sand 320 grit until it feels right, then spray again, 1-2 times then sand 400. spray, sand 600 etc. for nitro you need to wait preferely 3 weeks before final sanding and buffing.
also depending on your equipment what thickness you get ( how thin you thin your nitro with the thinner.)
I am no master of this yet :D still learning as I go.

Quote:
Wait a month, sand with wet 600, or 400 if bad spray job,
then start with polishing compounds that you like.
I think Alan ment 800-1200 before buffing !!!?
most end up with 1200-2000 wet sand before buffing, again depends on equipment used. (hand buffing, smaller machine, or large buffing wheels.

Lars
Author:  WudWerkr [ Thu Mar 24, 2011 2:36 pm ]
Post subject:  Re: Finishing procedure
Thus Far mine has been spray spray spray , sand sand sand , spray spray spray , sand sand , buff buff buff throught the laq [headinwall] start ALLLLLLLL OVVVVER !! [headinwall]
Author:  B. Howard [ Thu Mar 24, 2011 7:15 pm ]
Post subject:  Re: Finishing procedure
Amount of sanding depends on how well your finish flows before it flashes. The right reduction/ retarder mix is essential. 320 between coats will help keep orange peel from building up if flow is not the best. It's a real good idea to get a mil gauge and check how thick you are hanging your wet coats. I like to hang 3-4 mills, depending on your reduction this will usually yield about 1 mil or a little more cured finish with a pre-cat type lacquer. You want to end up with about 4-6 mils of finish after final sand and buff, get the lacquer to thick and it can craze. Proper spray technique will do a lot to improve wet flow and cut back on sanding required , thereby also the number of coats required. Take the time to set the spray pattern properly (I like 4 at 4 for small things like guitars, but whatever you are comfortable with). Remember to keep the air-cap parallel to the surface being sprayed and use complete strokes right off the edge. keep the distance between the air-cap and the surface a consistent as possible and keep the rate of travel constant as well. Don't forget to keep your overlap consistent too, about 40% is right for most guns as purchased, but bar patterns such as Devilbiss offers can require much less. Do not fan the lacquer on, you will just increase the amount of sanding needed. This info is not necessarily based on finishing guitars but rather cabinetry as well as cars and motorcycles. Best advice I was ever given on spraying finish was try to spray like a machine, be a robot.
Brian
Author:  Tim L [ Thu Mar 24, 2011 8:00 pm ]
Post subject:  Re: Finishing procedure
Sondre,

I have had good luck, and positive comments, using the schedule from the '95 GAL lecture.

Goes kinda like this:

10% laquer wash
20% vinyl wash
Sand back to bare wood. This seals the pores and gives them a bit of depth
Repeat the first 2 steps and then fill
10% wash
add color and then another wash if that's what you're doing
shoot 80-100% laquer 3 coats back & 2 coats top
Drop fill if necessary
sand back 400, I kinda level here but not perfectly
repeat the 80-100 shoot 3bk & 2top
Block with 600 & 800
shoot 50% wash and then let it hang for as long as bearable. I normally try for a month but if I have a lot of free time I get antsy after a couple of weeks
Block with 1200-2000
buff

Using this I have been able to achieve a flat finish and keep the nitro fairly thin. The part that bothers me the most is the buffing. I usually just hit it on the wheel using the Mazzerna compound and then buff and polish by hand where needed.
I only do a couple of guitars a year and doing it this way I spend more time setting up and cleaning up than I do spraying. I do try to spray all 3 coats in 1 day and then let it sit for a while, before sanding, especially at the end.
Hope this helps

Tim
Author:  Sondre [ Fri Mar 25, 2011 10:06 am ]
Post subject:  Re: Finishing procedure
Thanks to everyone. Exactly what I wanted to know [:Y:]
Page 1 of 1 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/