En av POP-prosessene - Printing Out Paper. I bruk ca. 1865-1920, ofte tonet.
{{cite web |url=https://marcus.uib.no/instance/technique/8caa440c-c1b9-4a0d-8ab0-9b042c26c090 |title=Gelatin positiv POP |author=Avdeling for spesialsamlinger |accessdate=Tue Feb 11, 2025 |publisher=University of Bergen Library}}