About a year ago I built a few book case style shelving units and a small cabinet under a utility sink. I used southern yellow poplar and finished it with Sikkens Cetol oil based interior clear satin varnish. No other stains or oils to color the wood.
I have noticed that the wood is turning dark. They are not exposed to any direct sun light and the inside of the cabinet is turning dark just like the outside and the doors are always closed. Because of this fact I don’t think it is being caused by light. Is it the finish or the wood that is turnig a dark grayish brown color.
If it is the varnish any recommendations that would work better next time.
Any help would be great.