No, I've just kept it out of the light. It is very bright yellow when first cut, then quickly turns dark deep brown/red with strong UV exposure. Its interesting; when I was cutting up the trunk I had to powerwash the pith area to get some ants & rot away; in the time I left the pieces to dry before sealing w/wax, the top side of the pieces turned visibly quite darker than the underside. This took less than 1 hour. This was an unusual mulberry; it was pretty old, and was almost 30" in diameter. Its hard to tell from the pic, but it was about 50 years old. The rings are uneven in the very base of the trunk, but it was a young tree. It stopped fruiting a few years ago, and about 1/2 the crown was dead. I took it down for too cheap for a friend, but got a lot of good turning wood & firewood out of it. The stump was pretty ugly; I was trying to get it as close as I could to ground level, but there was a bit of metal & concrete post not visible in the photo; the light area was what I cut off of the hinge about a week after felling the tree. The wood darkened within an hour or two from bright yellow to the orange-red color you see in the photo.