Direct Sunlight
 

I've read many posts here regarding the detrimental effects of leaving a guitar is direct sunlight. I like the look of a sun tanned top, but don't want to do damage to my guitars. So I'm wondering, is the bright light harmful, or just the excessive heat that can go along with it?

You really don't need direct sunlight exposure to achieve a tanned top. When I lived in the guitar-friendly climate of the southeast, I kept my D-28 and Taylor 12-string hanging on the wall in my little studio which had two windows. I always kept the blinds slatted such that direct sunlight didn't shine on my guitars, but all that UV bouncing around the room led to a nice golden tan on both of those guitars after a while...

http://i110.photobucket.com/albums/n...28/D-28018.jpg

Heat is a problem for guitars. Glue softens at around 150 degrees F.

In the open air on a sunny day there won't be a problem with overheating. However, if the guitar is in a black (heat absorbing) case in the sun, it might get hot enough to soften the glue.

I had a sunny day problem with a guitar stand. The neck support is covered with black rubber. The rubber got so hot it melted the finish on my Guild 12 string where the support touched the neck. This happened indoors with sunlight coming through a window :(

NCL ages and "yellows" over time. Direct sunlight is not good for the lacquer or the wood. Probably has less affect on Taylor's finish, as it is a poly based finish. I've protected my blond Guild from direct sunlight for 19 years and yet it's developed that beautiful aged glow about it. It just takes time. If you try to rush it, you may do some damage. Be patient..... ;)
Great color, eh?
http://imageshack.us/a/img339/782/016tht.jpg

Ultraviolet breaks down most materials very effectively, and heat does a pretty good job as well. Over a 2 or 3 year period, you may not notice much of a problem, but give it 10 or 20, and you definitely will -

My Martin J-40 Rosewood/Sitka developed that sweet honey glow with no sun, no direct sun at all, and was stored in its case for 11 years. It was never played or stored in sun..never, not even for 10 minutes. Aging gives the honey colored tone to sitka tops over time. When I had first bought it, the sitka top was almost pure white, like a very light cream for your coffee. By three years, it first started darkening, by 6 years darker, after 10 years, honey sweet and even across the whole top...almost honey colored. I would NEVER store my guitar in sunlight, and avoid it like the plague, unless it would require playing short periods out doors, that would be fine. Even then, I have other guitars for that purpose.

I try to avoid direct sunlight...