Installing Marquetry Rosettes
The first step in our next ukulele project class will be installing rosettes. The process will be gone over in class, but here is an over view.
Marquetry rosettes are made of various layers of wood glued up into a decorative strip. Normally the decoration has a band of either 1 or 2 solid lines on both sides of it. Many of these strips either cannot be bent to the tight radius of an ukulele rosette, or are very difficult to bend without breakage. The reason for this is that the inside circumference of the rosette is quite a bit smaller than that of the outside of a rosette. To check the difference in length, you can multiply the inside diameter by 3.14 and then do the same for the outside diameter. Depending on the width of the marquetry inlay, the difference in length of the strip is usually a minimum of 1/4" and sometimes a lot more. So, in practice the wood on the inside of the strip has to be made shorter. Attempting to bend a solid glued up strip results in breakage largely because the inside strip is trying to compress, but it can't. The solution is to partially remove the inside strip. On ocassion, I have had to make a number of separations of an inlay strip in order to make a tight bend. I've had great success with this. Depending on the glue, and you'll have to experiment, the solid lines can be removed by heating on the bending pipe until loose, heating with a flat iron, or soaking. The glue on the strips we will use was very good. The best way turned out to be soaking for 6-7 minutes in water at just below boiling (actually it was 210 degrees). At that point it was fairly easy to slice off the black and white strips with a single edge razor blade. The solid lines on only one side of the center decoration need to be removed, not on both sides. 1/2" of the strip was left glued together at the end.
Solid glued up strip and one after slicing.
Slicing the banding off. Leave 1/2" attached at the end.
FYI the following are a few more pictures of my process, though we will probably do it slightly different in class.
When gluing wood into wood, a glue like Titebond is preferred. It will swell the wood fibers, tightening the marquetry itself and make a better fit than epoxy or super-glue. You are also less likely to have broken glue lines that will show through the finish later.If the fretboard will cover the end of part of the rosette, the joint in the rosette can be left with a small gap. That gap must be completely filled with either a small piece of wood or something like 5-minute epoxy.
