Over time, the side of the horn exposed to the sun will want to return to being the nasty stringy cracked horn you started with, or at least that is my experience with big bison horns. My one and only bison horn powder horn took me four hours with a horseshoe rasp to get rid of the cracks, valleys and such but I ended up with a polished beautiful horn. And then nature took over. The horn wasn't ruined, but it didn't have the appeal it did when I finished it.