You need to do an oxi-clean treatment for a fairly long time. Get some of the powder oxi-clean (the stuff for your clothes) and place it in enough hot water to submerge your starbenza scales. I don't know the ratio of oxi-clean to water. I just take a scoop and dump it in lol. There are plenty of tutorials and threads instructing on how much to use(not that it matters too much. Prior to soaking your scales in the oxi-clean solution be sure to clean your scales throughly with soap and water. After I do that I tend to dunk and wipe the scales in rubbing alcohol to try to remove any residual oil. After cleaning the scales put them in the oxi-clean solution and let them soak. I like to change the water and add new oxi-clean every 2 hours or so. I soaked my scales for a total of 5-6 hours to achieve the bronze finish. The dark bronze look doesn't really last though and your finger oils turn the color into a dark grey.
If you want a really rich or deep bronze color that will stay I'd recommend electro-anodizing. You can send your knife to people like maprik on this forum or if you're on a budget make your own electro anodizer with some aligator clips + cables along with some 9.6 v batteries. Here's a video I found explaining how to set something like that up: (you should be able to attain bronze with just one 9.6 v battery)
https://www.youtube.com/watch?v=YOV5A22t4oY