Inside Finish

[tomb]

I am a mando and guitar at home player. I am starting with a dulcimer build in hopes to continue with more challenging builds in the future. I have done some wood working but never a instrument. Does the inside of the instrument recieve any type of finish? Can anyone recommend a good finish for a first timer?

[Big Joe]

Some builders do seal the inside of the instrument before they put the back on.

[billhay4]

Big Joe is correct, but most don't finish the inside.
If it were finished, I would think shellac alone would be used.
Bill

[sunburst]

A good finish for a first timer depends on what equipment and experience you have. If you don't have spray equipment or are not experienced with it, Tru oil is a good choice. There are spray-can lacquers, but they require some amount of exhaust or at the very least cross ventilation. There are brushable varnishes, padding lacquers, shellac french polish, etc..

As for finishing the inside, some do it to seal both sides of the wood. If you've done some wood working you may be familiar with the concept of 'balanced construction', often said 'what you do to one side do to the other side'. The idea is that coats of finish, layers of lamination, whatever needs to be done to both sides so that stability is improved. Some builders apply that to instruments...sort of. Obviously, you cannot apply all the same coats of stains, sealers, finish, sanding equally between coats, and buffing, equally inside and outside of an instrument, so it's not balanced construction anyway. No finish completely seals, so there will be a difference between the inside and outside whether the inside is finished or not.

Many repair people will say the inside of an instrument should not be finished at all because it makes repair work much more difficult later.

For those reasons and more, I don't think it is a good idea to apply a finish to the inside of instruments despite the fact that it is done by some top builders.

[tomb]

Thanks for the replys. Sunburst...I am used to sealing both sides of wood to avoid warping. It does appear that the instruments I have are not finished on the inside. I also want to make sure what ever finish I use will not affect the tone. Do you think using hide glue is required? What do you use to finish the neck?

[John Flynn]

The only build I've ever done was a dulcimer from a kit. I had hoped to do some more challenging stuff later, but decided I'd rather be playing than building. It was definitely an exercise in "luthier appreciation," though. My hat's off to all the builders out there.

I did an oil finish. It went really well and was pretty fool-proof, which is what I needed! You are right to seal the wood first, though. I learned that lesson too late. While I guess hide glue is the gold standard, I used Titebond and it worked fine.

[sunburst]

...I also want to make sure what ever finish I use will not affect the tone. Do you think using hide glue is required? What do you use to finish the neck?

A good finish (thin and well applied) will not affect the tone much one way or another, but it is as likely to improve the tone as make any other change.

Hide glue is not "required", though in general I think it is the best glue for most joints in a stringed instrument.

I finish necks with the same finish as the rest of the mandolin, and that can be lacquer or varnish. I've done several different varnish schedules.