I have a flat display made of many pieces glued together. The project took many, many hours.  It is made of exotic and domestic woods. It is about 10 years old and the wood color has darkened a lot.  How deep does the oxidation go? Can I sand down without destroying it? Is there any way of preserving the color if I can sand it down?

 

I believe that a lot of the color change is due to the presence of light. I would think that the color change, cause by light, wouldn't go too deep.

 

I lucked out a got a timber framing piece from a copula that was 150+ years old. The outside was black with years of smoke, dirt and rain. The dark color was less than 1/8" deep after all that time. 

Can anything help to slow or stop in a thin piece like what I have?  

3 hours ago, Ron Altier said:

Can anything help to slow or stop in a thin piece like what I have?  

keep the UV spectrum away/off of it...

You could get a piece of "Art Glass" which has UV protection and put it over it.  This will help a lot but is not complete protection. 

Two things that cause the darkening are UV from the sun and moisture in the air. The darkening may only be a surface condition, but the density of the various woods might play some part in how deep the darkening has penetrated. You didn't say how thick the display is. Sanding may be an option, but once it is sanded, it will only darken again unless you protect it from direct sunlight and somehow seal it from the atmosphere. If the display could be moved to a vertical position from the flat position, this could significantly reduce the UV effects.if it is exposed to direct sunlight.

Most logical suggestions have already been given; others to consider...(1) assume no one smokes in the house or room where located (2) display is not near kitchen where smoke, steam etc. can carry particles over time to be absorbed in the wood (3) not located near a forced air HVAC register..

 

An option to sanding might be using a hand scraper...my $.02

Put it in a pitch black room and never open the door again. But then why. Might be the same reason 2 seconds after an apple has been cut open it starts turning brown. It's actually pissed at you and is getting even.

It is my understanding that even home lighting will darken wood. I have left cherry partly exposed in the shop and when the covering piece is removed there will be a light area that was covered and darker area exposed.