Monobath R4, Lani Irwin and Alan Feltus

I have been experimenting with monobath processing for a few months now, as part of a research project with Bob. His R3 used Ammonia and Ammonium Thiosulphate, but I found the odour levels too much to work with, so I developed my own R4, which is currently in its 8th incarnation, and is odourless by using Sodium Hydroxide and Sodium Thiosulphate. Since I am no chemist, the whole process has been rather fun, and involved my adding more of one and less of another component until I started to get results that I like. Since the aim has been to get close to the ease and quality of Polaroid Type 55, I made adjustments to my monobath until I got similar midtones.

The other evening, just before my parents left Edinburgh, I took a few shots comparing T55 to Efke PL25 in my R4, and the results are most pleasing.

On the left you see the Polaroid Type 55, and on the right my monobath test, then below the FP100c45 and the DTR positives from the T55. I think the slight difference in density is more due to the 1/3 stop speed difference of the stock, as I was unable to adjust exposure that little on my Pacemaker.

These were shot with the Dallmeyer Pentac 8″ f2.9 (interesting lens).

My current monobath uses HC110, boosted in PH, buffered and fixed, also with a buffer. the PL25 was processed for 5′ at 20c, but the process terminates before that time.

Tobias Feltus: