Official Luthiers Forum!

I am new to this forum and luthiery.  I am in the process of building my first kit guitar (a Martin laminated rosewood dred) and decided it wasn't enough of a challange , getting involved in a repair project.  Here is my dilemma: 

I purchased a Martin D15 that had a small 3" crack along the grain in the lower end of the back, between the last brace and end block.  Having read a lot of web sites during my educational build process, I decided to fix the crack myself. 

Using hide glue and 95lb magnets for clamping, I thought I could fix the crack and get away with a light sanding leaving the finish un-disturbed - wroooong.

The crack repaired well, however it did not fit together perfectly and left a high spot along the seam.  It has sanded down, down through the finish leaving a 3" by .5" oval spot of bare wood.  My questions:

When finishing this section, would it be best just to tape off the sides and simply apply a few finish coats over the whole back of the guitar or should I just finish the one area?

Does Martin use a stain on the finish of the D15 and if yes (since I do not have a spray compressor) can I brush on a stained finish and achieve an acceptable result?

Since this is a satin finish, I was going to purchase a aerosol can of satin NC from Stew-Mac for finishing - will this work?

My simple project has me over my head already - however this is a learning experience!  The good news is that the guitar will still sound great no matter what the outcome of the finish.  The other good new is that my kit guitar is still coming along well (body almost ready for finishing and final assembly.

Thanks

Jack McCurdy

welcome to the forum jack. someone who knows what he/she is doing will be along shortly.

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sweat the small stuff.

On mahogany Martin uses a stain-filler. While I can't tell you exactly what it is I have found the it is a very dark stain that is mixed into the filler . I use a mineral based filler and add the stain to the filer to make repairs.
    A light rub first with ebony then follow that with a dark walnut stain added to the filler. Allow to cure and away you go. That should work and you can tweak your technique using this as a stepping stone
john hall

before deciding to get any finish for the touchup it would be a good idea to find out what finish material martin is using these days. i had read that many were not being finished in nitro but can't recall what was being used instead.

When I toured Martin's factory last year, they were still using nitro for the finish. They took a cue from the automotive industry and now have robots spray the finish. Matching that stain filler is going to be a tough job. Good luck Jack and wlcome to the forum!

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Joe Breault
Merrimack, NH
Perpetual novice

Thanks to everyone for the help!!

Quick question, if the stain is in the filler, could I assume that I would not have sanded the coloring out and it would still be in the wood, thus allowing for only a clear coating of NC to cover the repair or am I assuming incorrectly?

No , if you hit the wood you took some color off. I have done my share of repairs on martin and have had a great result with the ebony then the dark brown stained filler.
I was at martin for a few weeks in 2000 for training and this is how they taught me to do that repair. It may notbe perfect but not many people will notice it if done correctly
john hall
blues creek guitars

Thanks John - that makes it much more clear! 

Once stained with the filler, a couple of coats of satin NC, sand and buff?  Best to do the whole back or just the affected area?

Jack McCurdy