Spruce Top Discoloration Under Finish

[Jack]

I have a classical guitar, hand-built in New York about two years ago--I live in Northern Utah. The finish is good and in tact, however, there has recently been a change in the color of the spruce top under the finish in a small area near the top of the upper bout--it has turned slightly gray.  The instrument has been well protected from excess heat and humidity has been controlled at about 50 percent.  Any ideas on how such a discoloration might occur?

[FRANK]

50% IS WHAY HIGH FOR ME MABY TRY TO DROP IOT TO 35%RELATIVE HUMIDITY I WOUNDER IF YOU CAN POKE IN A CAMERA OR A MIRROR TO SEE THE BACK SIDE?

[Jack]

Thanks, Paul,
45% is about as low as we're getting here with a lot of wet weather. I'll try looking around with a mirror. Let you know.
Jack

[FRANK]

IF I rember correctly Roberto veenn suggested that it be like between 35% and 45% relative humidity which will also take into consideration the weather inside and out .like i said IT WAS A SUGGESTION THAT I read from the notes from robeerrtoo veeenn 07 .

[griff]

Except for extremes, humidity has little effect on the guitar as long as the changes happen slowly. Equilibrium is the key.

If the finish is intact, then you're looking at the discoloration through the finish, and I would suspect that first. Do you know the type of finish used? Shellac (a common finish for classical tops) is fairly delicate and can react and blush from contact with a number of things. It's also fairly easy to repair in the hands of someone qualified.

Over-all I would say it's nothing to worry about, unless the area changes or spreads.

[Frank Ford]

50% is just about ideal for any stringed instrument - that's where our shop hovers year 'round, and we like it that way. 35% is low by pretty much anybody's standard. Sorry, but it's basically impossible to help diagnose a finish problem without having it in hand, and even then it can be tricky.

[FRANK]

yea frank but your shop is feet from the bay you could never get to wacky out there temp and humidity is constant is int it ?

[FRANK]

like you would be in AZ

[Ned Knepp]

Paul,
I won't speak for Frank but, as the crow flies, I live within 5 miles of the ocean. When Santa Ana conditions whip up the humidity can drop 20 points or more in an hour or so. I feel sorry for the weather people here because the ocean plays havoc with their predictions.

I don't think that Arizona is constant either, not really. I used to work in Tucson and Phoenix a lot and found that they have "monsoons" during the summer. These are huge thunder storms that come up and dump buckets of rain almost every afternoon for about 15 to 30 minutes. These can make a 100 plus degree day go from 65% humidity to 95% in an hour. It like the opposite of our Santa Ana winds.