Several years ago I showed a shot of this gizmo; a vacuum pump and fixture for gluing on guitar bridges. I thought I’d show some new shots, and go into more details. By using a system like this, traditional clamps are not needed. Such clamps can actually create varied amounts (hot spots) of compression, and the caul (or block) used below and inside the guitar can change the shape of the top if its curvature is even slightly different than the natural arc of the guitar. This can cause the top to vibrate in a less than free and even modulation. This can and does affect tone.
This system uses no block or clamps, only negative air pressure (-20 to -25 inches of mercury) to gently yet firmly join the top and bridge, with perfectly even pressure across, and no distortion at all to the guitar’s shape. The result is a perfect, evenly glued joint that rings like a bell and vibrates freely and naturally. You can see in the photos, that the rubber is stretched tightly against and over the bridge itself, pushing with just the right pressure to be tight, without being overly clamped.
I have tested carefully the tonal results both via traditional clamps and this system, and without fail, the tone is superior this way!