This viola came into the shop with its center back seam open from approximately the middle of the upper bout to the middle of the lower bout. Although regluing the seam itself was straightforward, its length made me want to add a reinforcing cleat from the inside. Rather than removing the back, I developed a method of locating the seam with reference magnets, then guided a specially made cleat into position through the instrument using a bent wire and a small positioning magnet. Once the seam had been securely glued and reinforced, traditional glue cleats were added where needed, and the repaired seam was sealed to help protect it from dirt and moisture. The following photographs document the repair and the shop-made techniques used to complete it.
Clean the Seam: Clean the open center back seam in preparation for gluing.
Stage the Clamps: Arrange the clamps ahead of time so they can be applied quickly while the hide glue is still very hot.
Apply the Glue: Work fresh hot hide glue thoroughly into the open seam.
Clamp the Seam: Align the two back halves and apply the clamps to close the seam.
Add a Reinforcing Cleat: Because the seam was so long, I decided to install an internal cleat for additional reinforcement.
Locate the Seam: Position two reference magnets on the outside so the seam could be located easily from the inside.
Make the Cleat: Shape a small cleat and drill a positioning hole through its center.
Prepare the Cleat: Soak the cleat in water so it becomes slightly more flexible.
Attach the Magnet: Secure a small positioning magnet to the cleat with a tiny drop of CA glue.
Apply the Glue: Insert a bent positioning wire through the cleat and apply wood glue.
Skin the Glue: Use a heat gun to lightly skin the glue, then apply a small fresh dollop to the surface.
Position the Cleat: Guide the cleat into position over the seam.
Clamp with Magnets: Use a stack of magnets on the outside of the viola to pull the cleat tightly into place.
Remove the Wire: Withdraw the positioning wire once the cleat has been aligned.
Increase the Clamping Force: Add additional stacks of magnets to provide greater holding pressure while the glue cured.
Remove the Magnets: After the glue had cured overnight, remove the magnets from the instrument.
Add Glue Cleats: Install traditional glue cleats where needed to provide additional support along the seam.
Seal the Seam: Apply a thin coat of clear lacquer over the repaired seam to help protect it from dirt and moisture/
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Note: Removing a tall stack of magnets from inside the viola takes a little patience. Since only one magnet will fit through the f-hole at a time, each magnet must be separated from the stack and removed individually.
