Photographic works produced by platinum palladium printing process generally have a warm black color tone, characterized by small contrast, delicate and smooth layers, unique texture and elegant tone, as well as excellent durable storage characteristics. Platinum and palladium are inert precious metals of the same group and are very stable. Generally, pure platinum tends to have a cool black tone, while pure palladium tends to have a warm brown tone. When platinum and palladium are mixed in different proportions, subtle and different tones can be adjusted.