Making A Spiral Rainbow Rosette
Originally Published by the Guild of American Lutheirs in American Lutherie #111
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At the 2011 GAL convention, I was asked by a few people about the construction of my spiral rainbow rosette. I use colored purfling strips and spiral them from the outside of the circle to the inside, with various filler patterns in between. In my original design I used all the colors of the rainbow, but I have since worked with different color combinations.
I install the filler first. In this example it is a sequence of koa, padauk, zebrawood & holly bindings, alternated to create four quadrants in a bookmatched look. There are two walnut triangles just below three o'clock and nine o’clock to fill the joins there and visually ground the movement of the strips.
Once the filler is leveled, I cut two new channels on the inside & outside for the rainbow pieces. (see right). These channels are partially in the filler and partially in the top giving a clean line to the binding edges. This size of these channels is not too important as the purflings are inserted until they fill the space. Just keep it artistic & balanced. It could also change with the number of colors you want to use or how wide you want to make each color.
I use 4.5" strips of colored purfling veneer. I dampen and bend them around a plywood disc that is about the diameter I want to use. (see picture). The bent veneers are still very flexible when they have dried, so the diameter only needs to be close. I then sand the ends of all the purflings about 1” - 2’’ back from the end, so they feather out or taper to a point. This sanding could be done before you wet and bend the strips. I use 120 grit on a hard block so they remain straight & even. It will clean and sand your fingertips so use a piece of cardboard or plastic to get the pressure to sand the end (below-left). Be sure to pull the strips or they will break. The taper should be smooth & even with a good point (below-right).
The purflings are then fit into the channel and placed in sequence being sure to push the tapered end tight into the bundle to avoid space. (Left). Note on the left hand side of the spiraled purfling picture the red segment is not yet tight into the grove. Lengths of purfling are pushed until they are tight. I start at the inside & add strips until they are moved to the outside as new ones come in. This creates the spiral effect (Below). You can work from left to right, or reverse that to make the spiral go the opposite direction.
Once all the segments are dry fit, I trim the ends under the fingerboard area. Then check for space. On this rosette I have two spirals & the inner one rotates one way, the outer spiral rotates the opposite way (right). On this rosette I also made the rings have bright colors on the inside ring where there were dark colors on the outside, and vice-versa (below). This was done to contrast the difference so people would notice it more easily.
Then the purflings are carefully removed in the sequence they fit. They are placed around the rosette to maintain the order (left). I only glue one channel at a time using30 minute epoxy. I put epoxy in the channel walls & floor, then paint the outside of each strip. They are inserted as soon as the glue is on them. This helps to keep them in order. They slide into place easier with the glue as a lubricant. If I am making a true rainbow, I keep the colors in sequence of the spectrum.
Once the glue is dry, I level every thing with a scraper (left), being careful to only scrape in line with the grain of the top wood. I angle the scraper following the line of the rosette in each of the four quadrants to keep the scraper from snagging the purfling at 90 degrees and tearing it out. Scraping glue along the side of the rosette is best done by angling towards the glue before sliding over the rosette rather than coming off the rosette to the glue and top. Also be careful not to scrape the top across the grain. This creates tearout or dips that are difficult to clean up . Sanding should only be done with a hard block as the softer wood will sand quicker than the harder rosette woods. You want to keep it very level.
The final rosette (below) is ready for filling any small gaps and the space under the fingerboard. Then a light sanding with 220 will smooth it with the top just before finishing.
The rosette shown here (above) has a herringbone design with a blue-yellow-green-red strip separating them, one color per quadrant. The inner herringbone is slightly narrower than the outer herringbone. It is also slightly offset so the actual widths vary. This, coupled with the spirals moving in opposite directions, creates an interesting optical illusion of movement.
My first spiral in 2004 used the rainbow colors in sequence with a combination of .3mm & .5mm pruflings. It was difficult to keep the .3mm from disappearing below the surface, squeezed by the larger stiffer .5mm purflings. Also, .3mm isn't enough thickness to be highly visible. When I did it again I used all .5mm strips.
In this Spiral rosette (above), I added color to the inner & outer areas. The chevrons are bordered with yellow and blue to maintain a lightness to the look. I kept the spiral colors simple, only using multiple strips of only three colors to get visible width.
My latest rosette is on a classical guitar with an ancient Kauri top. It is a bold spiral in four colors. (above)The band is very wide so the spiral stands out to the viewer. If you look close you will see some filled space where the tapered ends weren’t pushed all the way to fill the groove. This may also be avoided by making the taper a little longer. The glue may have been setting or too thick. With this many strips, working quickly is important. Personally I find this too bold and prefer the subtler bands of color.
Color in any rosette brightens the top. Finding a tasteful design that is easy to install is a delight.