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PostPosted: Sun Feb 19, 2017 11:31 am 

Joined: Fri Mar 03, 2006 7:09 pm
Posts: 5509
Location: Hegins, Pa
Many of us started with little info and learned as we went. I was lucky in that I was around wood work my whole life and learned prep and filling early. Martin's training when I was out there for my authorizing was intense and very useful.

To say prep is the most important of the steps goes without saying. If there is on mistake many beginner do is to sand to too fine a grit. Martin doesn't go past 220 to allow a bit of tooth for the finish to adhere to .
Gun set up is also important.

my schedule is pretty much standard
A stain
B seal
C fill
D seal
E finish
I do this often in 2 steps
the first is to use a bit thinner mix with a retarded to allow good flow and evening of the surface. It cuts down on the orange peel effect

Also if your gun is not set right and your drying product before it hits the surface you will have a rough time.
I use about 50 50 but the thinner and retarder are mixed together. I use about a 30 20 thinner to retarder for the first coat then refill the cup with a 30 thinner finish for the 2nd coat.
I will shoot the 1st coat within a few min of the last seal coat to get a good burn in
the 2nd finish coat will be applied about 30 min after the first then the rest of the coats about 45 min to an hour apart.
I will use about 2o thinner and a touch or retarder depending on the conditions. The faster it wants to dry the more retarder.
I will place a business card in the sound hole so I get an idea of coverage. I am shooting for about .016 thick in the green lacquer this usually shrinks back in a week or so. After 2 weeks to cure I would level sand
started with 600
then 800
then buff.
If my finish seems too thin and I see any burn through I hit 3 coats and allow a cure and level sand again.

I can say that making a good sounding guitar is a lot easier than making a good looking one.

Filling was the harder of the finish skills to learn as it is all about prep. If you short cut the prep it will show in the end
this is for nitro lacquer.

All I can say is you have to practice. In most cases I have seen here in my shop from students it was they didn't take the final steps far enough. One was so scared to level sand that he left too much finish on , and once I showed him how to read the finish he learned that there are signs to watch for. Also learning to mic a finish is a big help. I always measure around the sound hole in the raw I know my base to the raw wood . Figure about .006 till your done at a min. .012 max

John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
Board of Directors of Association of Stringed Instrument Artisans

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