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From Gryphon's Little Shop of Horrors
Heat Stress!
© Frank Ford, 4/6/98; Photos by FF

Excess heat is the most unrecognized and destructive forces that act on stringed instruments. I'm talking about the kind of heat that builds up in parked cars. It's the kind of heat that kills the family dog in short order.

It's the kind of heat that drives out moisture and causes instruments to crack. It's the kind of heat that causes glue to melt. It's the kind of heat that causes necks to warp.

How hot is it?

My car can make it to 175 degrees Fahrenheit in only 15 minutes on a hot day in the sun. At that temperature, it's not long before the inside of an instrument case gets to be hot, too. At around 140 degrees the glue that holds modern instruments together begins to turn to liquid. LITERALLY.

Let me show you some of the really common heat stress problems that I see regularly.

This Martin D-18 was left in a hot car:

The glue lost all its strength and the bridge simply came loose completely. I know that's what happened because I can see little "strings" of glue underneath, showing that the glue stretched as the bridge was lifted off the face of the guitar. This can ONLY happen in high heat.

Because the strings anchor under the face of the guitar on the bridge plate, the bridge can't fly off all at once. A classical guitar bridge usually does, because the strings are tied on and don't go through the face of the guitar.

This guitar was lucky. It's owner saw the problem right away and loosened the strings before the top suffered more damage.

Here's a D-28 that wasn't so lucky. The glue melted in the heat and the bridge came loose and was subsequently reglued by a well meaning repairman. Apparently no one noticed the severe wrinkles in the top, extending from the corners of the bridge toward the end of the guitar:

I hope the photo is clear enough. By the way, that's a round desk lamp and the reflection is distorted by the wrinkled spruce top. When I see a wrinkle this severe in this location, I can tell that the brace has been pulled loose inside the guitar:

See that light gap right at the back corner of the bridge shadow? That baby's really loose! With any luck, I can reglue it and restore the much of the strength of the top brace. This is serious stuff, because regluing a brace inside means adding new glue to old glue, and the strength of the bond will be compromised. Usually that's not a problem the first time. . .

When I go to vintage guitar shows, I'm always amazed at how many old guitars I see with this telltale top damage, yet I've never seen either a dealer or customer looking inside a guitar to check for problems

Hey, take a look at this guitar neck:

Its was left too near a heater and this happened to the finish on the neck without any damage to the case. No question what happened here! I've seen this kind of finish damage in hot cars, too.



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