Wednesday, November 2, 2011

Tools and Techniques for Carving Lute Roses

The collection of items in the photo is all of the tools that I needed to cut the theorbo triple rose. At the top is a bottle of mucilage that I use to glue the rose pattern into the belly wood. Mucilage is a glue usually associated with children's crafts. Since I cut the pattern from the front I need to remove the remaining paper of the pattern so I want a glue that is easy to remove. Which it is. Next is a well used block of paraffin for lubricating the knives. The circle cutter is used for scoring the borders of the roses as I described in previous posts. Of the two knives that I used the first is an X-acto with a #11 blade. The second is a small violin maker's knife. Two sizes of small gouges came in handy for scoring the outline of the tighter curves of the organic elements of the design. I do use small chisels (not shown) for some roses but they were not useful for this design. I do use a small magnifying glass. I do all of my carving on a self healing mat.

I want to demonstrate several features of my carving technique so I made an enlargement of the rose pattern - one that would show up better in a photo - and glued it to a scrape piece of soundboard spruce. Using the violin maker's knife I score all of the lines on the pattern, firmly and precisely as possible.  In the photo at the left I am using the violin maker's knife because it has a thicker blade that is easier to control. If I  deviate from the pattern I balance the mistake by maintaining the proper width when I cut the opposing line.  Although I have reduced the soundboard thickness to 1.1 - 1.2 mm in the rose area it usually isn't possible to cut completely through the belly in one stroke. The elements of the design, especially the ones that align across the grain of the wood , are weak and easily broken. To prevent this I cut a "relief" to the line. That is what I am doing in the photo. You can see a bit of the paper pattern and wood curl up. This is accomplished by holding the knife at a 30-40 degrees angle while making a cut parallel to the original perpendicular one. The adjacent area has already been "relieved". 

Here I am making my final cuts. I am using the X-acto #11 because it has a thinner blade and is less likely to push the wood apart, fracturing the fragile rose pieces. I seldom use the #11 for the initial cuts because the blades are too flexible and are harder to control.

The direction of these cuts is important. Although it is not clearly visible, the grain of the soundboard runs from side to side in the photo. All of the cuts run across the grain at varying angles. To prevent the end of the exposed grain from grabbing the knife and throwing it off course I cut "down" grain or with the "nap". You can feel this effect by making similar cuts diagonally in each direction on a piece of spruce. A key to understanding the problem is to note that the direction of the cuts on opposite sides of the center element between the two marked areas are opposite. It is a good idea not to remove a waste area until the adjacent areas are completely cut. Making the final cut on one side of an element that is not supported on the opposite side can lead to breakage. Note: Lubricate your knife frequently with paraffin.

The border of each rose has a ring of diagonal blocks that are chip carved on their corners. I lay out the spacing for these with a template that I made specially for each rose.

 It is made with a protractor on a piece of poster stock. The circle of the rose border is marked off in five degree intervals and an area corresponding to the border is cut out. This template is positioned exactly over the rose border and taped in place. Now a knife cut can be made diagonally from one line to the next. The result is 72 equally spaced diagonal blocks. Two opposing edges of each block are now chipped off to create the final effect.

 I have finished the theorbo so obviously it is quicker to build them than to blog about them. My next post will explain my system for barring the soundboard.

 My theorbo's new home is the Music Department of Grand Valley State University in Michigan.

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