This shows how we position the new bridge and prepare the top.
Critical note: Use only Scotch Green "Hard to Stick Surfaces" tape for this operation. Do not use Frog Tape or any other tape around lacquer finished guitars.
The product shown below is the only tape that will not harm tender lacquer surfaces. Please see the page on this product. One exception: Do not use any tape on the gear head face.
Make a template from masking tape laminate. The 2 inch width is preferable. The laminate is alternating layers of tape laid long wise and crosswise. It's tape plywood! This should be at least 1/16 inch thick.
Trace around the new bridge, then use a very sharp Xacto to cut around the tracing. Here the cutting is complete. Just starting to lift the outside of the template from the cutting board. We leave the center part on the board. The board shown here is an old Corian cutting board.
Stick the template onto the top where you want the new bridge to go. Be sure to align with the top centerline and perpendicular to the top center seam.
Note the finish left by the original bridge installation. This is the Harmony company cost cutting procedure mentioned elsewhere on this site.
Glue Prep -- Before gluing the bridge the old glue residue and top finish around the edges are scraped clean.
Then the area is sanded and checked with a little straight edge to ensure there are no dips in the top after scraping. We fill those with spruce and scrape down to level with the surrounding top wood. We glue to clean, fresh spruce using hot hide glue. Below, note the all-around completely clean glue area. Scraping is not completed here, but you get the point. The tape template really makes this cleanup operation a snap. It acts like a barrier against which you can scrape without fear of damaging surrounding surfaces which will show after the attachment operation is complete.
We sand the top attachment area with 320 grit. Below are two samples. The paper on the left shows that sanding is not yet complete. You can see little nubs of finish and stain. This indicates more sanding needed.
On the right, you can see plain spruce saw dust. As soon as this shows, stop sanding.
The image below shows a 12 string bridge glue procedure underway. In this case, since the bridge is square, we just attached the tape directly to the top. No need to build, trace, cut and move to the top from another surface. Another caution: When laying the tape down on a top that is not perfectly flat, be very careful not to leave any tape under any part of the bridge that may be floating a bit until clamped. When gluing a flat bottom bridge to a domed top, it is very easy to get the tape stuck under the edge of the bridge. That makes cleanup super tough because the green tape does not want to pull out. That sliver of green tape highlights your screw up like a light house beacon.
Those monster Pony/Adjustable Clamp brand long reach clamps are wonderful. No deflection on these babies! Between the super stiff quarter sawn rosewood bridge and the one inch backing block between the clamp and the reinforcing plate, this setup produces force sufficient to further flatten the top as needed. Fortunately, on the guitar below, the top is almost flat, otherwise further fitment might be required.
Clamp for a few minutes, waiting for all of the squeeze out to stop. Then remove the template leaving the clamping set up as is. We wipe off all squeeze out and glue spill all around with dry paper towel bits. Use no water. Lots of wiping happens here. Don't wait for the glue to dry!
Normally, we can remove the old and install a new bridge with no damage to the top at all. The exception happens when the old bridge was installed in the wrong location. Since we only use bridges with a profile matching the original, some top finish damage may show. We try to keep this to a minimum. I guess that is why God invented lacquer touch up.