Platinum photography was a popular method of creating permanent photographs in the early 20th century, before falling out of fashion. The images produced using this process are incredibly matte and have an infinite range of tones, with fine detail that appears almost hyper-real. They are also incredibly stable, with images retaining their deep tones and detail for hundreds of years. However, the process has drawbacks: it reacts slowly to light, meaning that images can only be made using the direct contact printing technique. The advent of consumer 35mm cameras and the use of platinum in explosive production also contributed to the decline of this method.
https://whyisthisinteresting.substack.com/p/the-platinum-photography-edition