Crafting a Hand-inlaid Celtic Knot

Posted by Dusty - 2015-11-18 18:57:00

Celtic knot design inlaid in abalone on a curly maple harp pillar

It was the early '90s (no one remembers exactly what year), our 36-string harp had just been re-designed, and Ray and Sue were casting around for a classy way to decorate the new FH36B. As a group of Dusties stood in the middle of the store (this is back when our retail store and woodshop were in the same building) tossing ideas around, someone looked at a guitar on the wall and said, "Hey, what about abalone inlay?" Many guitar-makers were edging their soundboards with iridescent abalone shell, and there seemed to be no reason it couldn't be done on a harp.

To take it one step further, Finish Team member Heather Kinnowr designed a delicate, interwoven Celtic knot that could be inlaid in abalone on the front of the pillar. Popular from the very first harp we tried it on, the Celtic knot has remained virtually unchanged for more than 20 years. The inlay takes hours of detailed work by one of our most experienced craftspeople, and the result never fails to capture people's fancy with its understated and elegant sparkle. We are often asked how it's done, so here is Frank Posenke, 19-year veteran of our Finish Team and Celtic knot specialist (among his many other skills), to show you what the process is like.

 

Celtic knot channel routed in a harp pillar

The first step is to create a pocket in which to inlay the abalone pieces. Originally, the pattern was transferred to the wood using a pantograph router and an aluminum block template, which was made in a machine shop from the original artwork. Since the mid-90s, we've employed CNC (computer numerical control) technology to create the pocket, but the remainder of the process is much the same as it was in the beginning (with a few improvements by Frank over the years).

 

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The tiny pieces of abalone shell (seen on the left) will be framed by delicate strips of purfling (seen on the right), which are made up of contrasting layers of wood veneer in a black-white-black pattern. Frank carefully sorts the abalone pieces by their reflective properties and arranges them in a balanced sequence. This way, the "sparkles" will be spread out over the whole design, rather than clumped in one area and leaving another area looking somewhat dull.

 

Chisels and glue ready to start the inlay process

The master craftsman's tools...

 

Mitering the ends of the abalone strips so they come together in a point

To start, Frank miters the ends of the purfling and the first abalone strips so they come together in a clean point. Each piece of abalone shell is 1" long and 1/16" wide. One by one, they are carefully laid into the trough between the strips of purfling.

 

Piece by piece, abalone fills the trough, outlined by strips of binding

The purfling can bend around most of those corners, but the abalone isn't as flexible. It can handle wide, easy curves without breaking, but where a smaller-radius turn must be negotiated, Frank has to break the abalone into tiny pieces. If there are any gaps between adjacent pieces, Frank miters the ends with a sharp chisel to create a seamless connection.

 

Using a chisel to cut the binding

The Celtic knot will have a criss-cross pattern, so one line is cut where it will appear to pass under the other line

When finished, the knot will have a basket-weave pattern, with one line appearing to cross under the other at each intersection. When he gets to one of these cross points, Frank uses a chisel to cleanly end the line that will go underneath.

 

Applying super glue to hold the abalone in place

As you can see, the other line has continued "over" the first intersection, and will now go under at the second intersection. As he goes along, Frank periodically squeezes cyano-acrylate (super) glue into the channel.

 

Carefully marking his next chisel cut

The abalone Celtic knot is halfway done

When he's finished cutting, shaping and gluing in the abalone pieces and the purfling, the harp neck is sanded smooth and sprayed with several coats of clear lacquer, leaving the grain of the wood and the sparkle of the abalone to show through.

 

Finished abalone inlay Celtic knot on a bubinga harp pillar

Abalone inlaid Celtic knot stands out against this harp's black finish

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