Durability test number three is in the books. Using medium-fine silica-based sand as an aggressive tumbling media, 5 black-colored cartridges were tumbled for successively longer intervals to determine how much wear and tear the brass coloring can withstand.
![Test results of sand tumbling colored brass](https://i0.wp.com/nnbrass.com/wp-content/uploads/2022/10/Test3_a.jpeg?resize=1024%2C768&ssl=1)
![](https://i0.wp.com/nnbrass.com/wp-content/uploads/2022/10/Sand-Tumble_b.jpeg?resize=750%2C562&ssl=1)
![](https://i0.wp.com/nnbrass.com/wp-content/uploads/2022/10/Test3_c.jpeg?resize=768%2C1024&ssl=1)