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Hey Guys,
I received my Martin Jumbo Acoustic Kit today. I'm really excited to do my first acoustic build. I was about to to get started on it, but then I discovered that there were a lot of water stains on the mahogany sides. Is this normal? What do I do to get rid of them? sand them, etc... Should i return it and get a new kit? Shouldn't I just sand the whole exterior of the guitar? I have attached a photo. (I think) Thanks!
http://www.tdpri.com/forum/acoustic-hea ... ormal.html
Photos are right in the atachment. Thanks!

Congrats on getting a kit and starting this crazy journey! The marks should sand out. They are probably there from bending I am guessing. If you could post a picture that would help.

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Lance@LuthiersForum.com

Indeed, those look like surface stains that will sand right out. Good luck with your build!

Thanks guys! What grade sandpaper should I use?

I would wait until the box is all together - you will have glue squeeze outs to clean up and probably want to level your bindings to the sides. Start with 150 or 180 and go up thru the grades to 320, then do your pore filling and level that back with 320 before doing the final finishing.

btw - a cool trick at this time is to dampen the wood with a wet cloth - it will pop the grain and you can really see what you are working with.

Looks like nice mahogany, have you thought about how you want to finish it?

I think I want to do a satin finish. I've thought about it and I know that I don't want gloss because it smudges and my hands stick to it when I sweat. I love satin finishes. Any recommendation about how to do it?

Satin tends to be a little easier than gloss finishes, but basically the steps are similar. Instead of going through the final sanding buffing stages you stop at maybe 1500 grit and then lightly scuff the surface (0000 steel wool or scotch bright pad).

The real question is what materials and methods to use and that is dependent on what you have available. I think it is one of the hardest decisions for a new builder, so spend some time researching the options. They include, but are not limited to

- hand applying shellac dissolved in alcohol - so called French polishing. Very time consuming, usually gives a semi gloss finish. Traditionally used on classical guitars, violins, etc.

- hand applying a finish like TruOil (typically used for gun stocks). Doesn't require any special equipment and gives a nice semi gloss finish. I haven't done it but have read of some people who have a hard time getting it to cure properly.

- rattle cans of nitro cellulose lacquer. Dangerous, toxic, explosive..... but it does give a pretty good finish for an amateur. You can get high gloss if you want it (like maybe the top) and satin on other parts of the guitar. I did this on my first few builds and they are holding up fine.

- water born lacquer. IMHO it has all the advantages of nitro (appearance) with none of the problems. It does require a compressor and gun however which may be out of the range of a first time builder. I use it exclusively now and have done sunburst and other effects.

Its not too early to be thinking about this. If you followed my advice on the StewMac instructions and some of the building threads I pointed you to you'll start to see how others have done this.

http://www.stewmac.com/shop/Finishing_s ... 3&xsr=8297
I was thinking of using just a few coats of the clear satin finish option of this product.

This is what I DONT want:
http://www.bedfordbanjoshop.com/files/rd262.JPG

This is what I DO want:
http://dalymusic.com/store/images/products/f-d20-cm.jpg

The general rule is I don't want anything I can see my reflection in. I don't want anything my hands would stick to either. Just a smooth satin finish. Would the stewmac product be good for what I want? Thank you.

Yes, the StewMac lacquer is a good product and will give you the finish you want. Remember that it is extremely toxic and flammable - wear a respirator and either shoot outside or in an explosion proof area. This is what I used on my first couple of builds - I started with their paste pore filler, then built layers with their sanding sealer and finally the lacquer. I think I put about 24 coats on my guitars, and since I do like shiny finishes I buffed it to a high gloss.

About how many coats do you think I should do, since I want a smoother finish?

[quote="Telemaster] About how many coats do you think I should do, since I want a smoother finish?[/quote]

You'll have to decide that as you apply the finish. StewMac recommends 6-12, I have always applied more (click the instruction tab)

http://www.stewmac.com/shop/Finishing_s ... 7869450205

But that depends on how well you prepare the wood (pore fill and sanding) and how heavy you apply the coats. With lacquer you apply 2 or 3 coats per day, sand lightly the next day and then apply some more. Typically satin finishes do not have as many coats nor are they sanded and buffed to the final gloss. The SM sanding sealer is a thicker version of the satin finish and builds thickness faster.

I don't think I would worry about the finishing and sanding at this point. Keep it in mind and ponder your choices, but the box assembly is most important to your successful completion of the instrument at this point.
Some more important points are...do you have an accurate mold? Are you bending the ribs? How are you thicknessing everything? What glues are you going to use? Will this be a one time shot at building, or do you intend on making more instruments? How cashy are you? This could be a bit influence on what you buy. Do you have access to a shop?
As far as finish sanding, you don't do any on the outside till the box is completed and bound. Insides can be sanded with 120 to start, finishing with 400 and then steel wool and then vacuumed carefully before assembly.