Cannot keep a consistant BG color.. Help?

[photo1x1.com]

The stones sure are much smaller than the wood - hence the shallow depth. That of course is easier to light.
Can you show us some shots of the wood with the same setting?

 

[Designer]

So in essence I should re arrange the lights instead of changing settings?

Ordinarily, continuous lighting will work for product photography, but in this case, I would recommend you use electronic flash units instead. If you allow your camera to meter on each object, it is no wonder you are getting inconsistent results. Use flash, you'll be glad you did.

I've done a similar project wherein I photographed a couple hundred craft projects that are mostly bowls and plates turned of highly figured wood. I used two flash units (diffused of course), and left all the settings the same for all the objects, and did the minimum of editing. The only setting that changed was the focus, because each object was placed by me, and they were different in size and shape, so the lens just had to focus before I took the picture.