Paper Lining for Bowl Back Mandolin

[Jim Garber]

Strange that they would feature the FRONT side of that mold in the display, Jim.

Maybe you could see the business side of it from around back of the vitrine?


Not to argue with the museum folks, but you could CNC mill up that mold today in a rather straightforward manner.

Then use a multi axis mill to locate and drill all the pin locations in advance.

Mick

I could not see the front otherwise I would have photographed it. I did visit a very experienced luthier in CT who has one of these forms from the Martin factory and he did show me the pinholes. I just don't think that took any photos of it, unfortunately.

[sebastiaan56]

It might be partly my fault and the discussion here makes me think that I was not right in promoting that opinion of the paper used to release the bowl from the form. However, I must have heard it somewhere back than and also possibly may have come to that conclusion after seeing sites describing the forms used for building these.

Actually, a luthier I know in Connecticut showed me an original Martin bowl form with multiple pinholes to hold the strips while gluing. This, of course, has absolutely nothing to do with lining the bowls.

Molds are always coated with wax or more recently varnish. This is to prevent the glue sticking the staves to the mold. From what I saw in Naples there is no practise of papering the mold and then attaching the ribs. This makes sense to me. The process is to get the bowl off the mold then lather the inside of the bowl with hot glue. When this is dry another layer of hot glue is added and then the paper is stuck on to the inside of the bowl. The paper is then lathered with glue to make it really limp and pushed into the inside of the bowl by hand. The point is to get it to fit the bowl exactly. It is then left to dry.

The cool part of this system is that the glue shrinks as it dries. as does the paper. this pulls the the bowl together. It greatly strengthens the bowl. So it makes sense to use long fibre paper and most kraft papers are in this category. It also covers imperfections in bowl construction. This is important in a production environments.

I also saw bowls with carefully aligned pin holes. Well used ones at that. Whether by design or long usage by skilled luthiers I cant say but having made a few now I do tend to pin them in pretty much the same places each time.

Using shavings is basically the same as using paper. Im sure they are pressed into the rib joints with as much vigor as the paper. I prefer paper because it offers the decorative opportunity. But It’s not important to functionality.