Adding color to hide glue for an invisible repair

The finish on this old Gibson A-50 mandolin shows its age

And that’s fine with me. But at the neck joint there’s some damage and a gap where the binding has pulled away from the side.

To repair this tiny area, I mixed hot hide glue and ColorTone stain to create a colored glue to match the surrounding finish. This way, the glue filled the gap and touched up the finish at the same time. That's handy!

I didn't used to think of hide glue as handy. Before I started using an electric glue pot, I would heat a jar of glue in a pan of water on the kitchen stove. It was a hassle, so I didn’t use hide glue much.

That was a mistake.

I was missing out on the best glue for about half of the work I do. Now that it’s right here by my bench, warmed up and ready to go, I use hide glue every day.

A glue pot can hold way more glue than I need for instrument work, so instead of filling it with glue I fill it with water. The glue goes in a small jar sitting in the heated water, with plenty of room for my gluing tools:

1. Long-handled glue brush
2. Glue jar (with the green cap, almost submerged)
3. Mixing cup (In the cup is a Q-tip, clean hot water, and a small brush I use to clean the glue brush.
4. Pipette filled with hot water
5. Thermometer
6. Hot wet rag
7. Next to the pot is a plastic cup, bottom-side up, with a smaller plastic cap on it. On the cup is tobacco brown Colortone Stain, and the little cap contains extra-thick hot hide glue mixed with a little of the stain.

A repair magnet in the bottom of the mixing cup holds it to the glue jar. This anchors the lightweight cup, and it’s a convenient way to lift the glue from the hot water.

I’m not painting with the glue, I’m just touching the glue-filled brush to the mandolin, using the drop-fill technique.

I love being able to clean hide glue with hot water and a Q-tip. Even though it’s already started to set, I’m still able to clean it off the binding. In the morning it’ll be really hardened; then I’ll use sandpaper and an X-Acto blade to smooth away any rough spots.

If more glue is needed, no problem: I’ll just warm up the leftover stained glue, melting it so it’s ready to use again. As a last step, I’ll brush a little fresh-mixed shellac over this repair.

What’s so hot about hide glue?

I predict you'll become a card-carrying member of the Hide Glue Club!

• Hide glue dries crystal-hard, unlike plastic resin glues, so it doesn’t dampen tone.
• Hide glue joints don’t creep. Maybe you didn’t know this, but over time under string tension aliphatic resin glues (like Titebond) will stretch a little. This is called “creeping.” It’s not a problem with hide glue, which isn’t plastic-like in its makeup.
• It’s really strong, similar to epoxy.
• Joints can be heated/steamed back apart. Just like vintage!
• Water-based, for easy cleanup.
• It was used on the instruments we want to work on most. It’s what was used on those vintage guitars/mandolins/fiddles that we like to see come across our workbenches.