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Quick Cauls

This technique's a classic! Styrofoam or Friendly Plastic are two materials that make great imprint patterns for creating protective cauls.



i-quickcaul Updated 05/07

Classical guitar maker Thomas Humphrey shared this trick for clamping a classical bridge, and determining bracing alignment on cedar-topped instruments…

“When you're clamping the bridge on a classical guitar you must have a well-fit caul on the inside for the clamps to contact. Cedar tops in particular keep me on pins and needles because they're so fragile; they dent and ding easily, and excess clamping pressure can crush the wood fibers. Also, with cedar tops you can't use the old light bulb-inside-the box trick to see through the top to locate the braces (for making a caul) because cedar doesn't illuminate like spruce does. I use styrofoam to take an imprint of the top bracing before transferring it to a wooden caul.

 
“Make a caul from a piece of wood 7" to 9" long x 1-1/2" wide x 3/4" thick (or whatever goes in and out of the soundhole easily). Then double-stick tape a 1/8" to 1/4" thickness of styrofoam to the block. When the block's clamped lightly in place, the styrofoam takes an imprint of the bracing pattern. Remove the block and saw along the imprint marks, right into the wood. Remove the styrofoam, deepen your saw cuts to match the height of the braces, and chisel out the waste to make channels which fit over the bracing. Chamfer the sharp hard edges of the caul to keep them from denting the wood, and be sure that the caul matches the curve of the top and/or the bottom of the bridge if there is a curve.”


Friendly Plastic can be reshaped again and again — just drop it in hot water!
Friendly Plastic makes protective cauls that conform perfectly to hard-to-clamp areas. Friendly Plastic pellets congeal in hot water to become a malleable mass. Form a small lump (you can use a small flat wooden block as a base if needed), and clamp it lightly against the intended area, such as an interior soundboard brace. In a few minutes it hardens into a tough, perfectly seated reusable plastic caul that can be clamped at full pressure.

The braces won't be damaged, and you won't have to spend your time making custom wooden cauls in complicated shapes. You can make perfectly seated cauls for clamping bridges, braces, fingerboards or curved surfaces.






Classical Guitar Bridge
Classical Guitar Bridge

Bridge Clamping Caul
Bridge Clamping Caul

Flush-cut Saw
Flush-cut Saw

Double-stick Tape
Double-stick Tape

Friendly Plastic
Friendly Plastic


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