Regarding Art300 paper, I just recently used some of mine properly and took note of what happened. I was previously using two baths TF3 fixer with water as a stop bath - that does not even come close to working with Art300.
So, I just switched to regular fixer (again 2 bath) and acid stop. In freshly made acid stop, the art300 paper actively bubbles for almost 2 minutes. Streams of bubbles from the edges and bubbles from the field of the paper, as well. So, I imagine in addition to the staining seen on the edges, there is likely staining in the field of the photo in some instances, when the developer is not fully stopped. I think it would be ideal to rinse the paper before fixing. However, I did that with a sheet and didn't do it with a sheet and didn't see any difference.
Thanks for that follow-up, Don. For what it’s worth, I’m now a good 1/2 year or more into this topic of Art 300, and I can continue to second NB23’s assessment. I’ll write out my routine (inspired by him) for future readers of this post:
*IF* you are having staining issues with this paper, and *IF* you wish for an “excellent” result using Photographer’s Formulary Residual Hypo Test Solution, then consider the following routine:
1. Use fresh chemistry when you’re ready to make a “keeper.”
2. Stop for at least 60 seconds. (I do 120).
3. Fix in film-strength fixer (1:4) for 60 seconds.
4. Wash in briskly running water for 5 mins.
5. Use hypo clear for 10-15 minutes.
6. Wash in warm (20 C) water for 60 minutes.
I am aware that this does not fully gibe with the Ilford data sheet. No, I cannot explain this.
I am aware this could be predicated on my water supply (Ph, or minerals, or whatever), or an erroneous/misplaced emphasis on the “excellent” result for the hypo test.
But, after many, many ruined prints (with visible staining), or prints that failed the hypo test, this is what is consistently working for me. Hopefully that is helpful to someone.