Many blogs and forum posters claim that photo paper has gelatin in it, and therefore isn’t vegan.
I tried to track down a source for this claim, but the best I could find was the gelatin silver process.
The gelatin silver process is the photographic process used with currently available black-and-white films and printing papers. A suspension of silver salts in gelatin is coated onto a support such as glass, flexible plastic or film, baryta paper, or resin-coated paper.
This used to be common, but it’s not that common in modern day printing.
Modern paper, from what I could find, is typically lined with polymers (i.e. plastic), which is vegan.
For example, Ilford resin coated paper is vegan-friendly:
Resin Coated Inkjet Papers are the papers most people regard as ‘photographic’ because they’re the type that your typical mini-lab uses. These papers are made using a layer of (usually low grade) wood pulp, over which a layer of plastic is placed, usually polyethylene
So, as far as I can tell, most photo paper is vegan.
A long time ago it wasn’t, but technology has evolved.
It’s hard to know for sure, since ingredients aren’t typically listed alongside photo papers, but you can contact a particular manufacturer if you’re really concerned.
Let me know if you find additional information either way and I’ll update the page.
On a side note, it does seem like film contains gelatin, so vegan photographers should stick to digital.