Friday, 3 December 2010

Too hot to handle

 Its officially summer here in New Zealand and the weather is warming up. The acoustic season has begun - there's nothing better than sitting out on the deck strumming a few chords, dog by your side and a cold beer on the go.
 There is a downside to it all - in the last week I've had two guitars in the workshop with the bridges clean off. They had been left in cars. 
 You wouldn't leave your dog or your kids in the car for hours on a sunny day and your guitar will be just as unhappy.
 Guitars are put together with 'heat reversible' glue (usually an alaphatic resin). This makes it possible for me to do my job. If I need to take your guitar apart I can by carefully applying heat. If you leave in the car too long a guitar will dismantle itself.

  This guitar is a nice, Spanish made classical guitar. It spent the afternoon in its case in a car with the outside temperature about 25C. Of course it was a lot hotter in the car.

 Whan the case was opened the bridge was off.

 As you can see, the glue has failed - there's still glue on both surfaces.
 The first thing I did after taking the strings off was check the internal braces. It is very common with repairs like this for there to be more damage on the inside than the outside.
 Everything was fine inside to I imagine the bridge came off before the string tension pulled the top too out of shape.

 I remove most of the old glue with a sharp chisel.
 Incidentally, I measue the sharpness of my chisels by testing them on the hairs of my left arm.

 That's a nice bald patch with no rash - a sharp chisel.
 Now you know how to spot a luthier.

 I use the belt sander to clean up the underside of the bridge.

 This bridge has a slight warp that I take out with the sander.

 I score the underside of the bridge to help give the glue a key.

  I mask off the bridge area on the body. This helps with both alignment and glue clean up.

 I use five long reach clamps to attach he bridge. The glue is Titebond Alaphatic resin.
It is very important to use a reversible glue. If this bridge had been held on with epoxy in all likelyhood it would not have failed. If it hadn't failed the top would be warped, there would be untold damage to the braces and the result would be a much more involved repair.

  As it is the guitar is ready to play again with no visible evidence.


Sammy doesn't like being left in the car either  - he'd rather be showing off his catching skills on the beach.