When evaluating black carbon paper, the most critical factor is the coating weight and uniformity, which determines the clarity of the transfer. For high-volume business use, look for 'smudge-proof' or 'wax-free' formulations to ensure clean copies. The base paper weight (typically measured in GSM) should be between 16gsm to 22gsm for optimal balance between durability and the ability to transfer through multiple layers. Additionally, verify the reusability factor; premium carbon paper should allow for 30 to 50 clear impressions from the same spot.