(Not a scientist, just a hobbyist.) Red phosphorous is an ingredient in the original paper’s process. https://patents.google.com/patent/US6110438A/en https://

(Not a scientist, just a hobbyist.) Red phosphorous is an ingredient in the original paper’s process. https://patents.google.com/patent/US6110438A/en https://patents.google.com/patent/US6110438A/en claims that black phosphorous can be made from red phosphorus using a vacuum and hundreds-of-C temperatures. Both of which people have done. Seems very possible.