blackening silver halide

[ron olson]

I have just begun experimenting with blackening silver halide plates per the procedures defined by Jeff Blyth as a means of eliminating painting silver halide emulsions.
We used Jeff's recipe:
650ml industrial methanol (sold in U.S. car parts shops as "Heet" a fuel antifreeze).
350ml water
0.5g sodium borohydride

The initial results are extremely promising in eliminating the messy, sometimes risky business of spray painting and the blackened plates exhibit a very finished appearance with excellent contrast. For Agfa plates we used our standard post-processing starting with collodial developer, then after thorough drying (listed by Jeff as a mandatory step) we immersed the green images into the blackening solution for ~1-2 minutes. We then washed the plates thoroughly and proceeded with "Blyth colour-tuning" as reported here previously. Once dried the blackened plates attained the same finished amber color as as their unblackened counterparts. My hat's off to you Jeff once again for simplifying our production procedure - I will track the experimental plates for stability over time and report back to include using the procedure on other emulsions.

[Colin Kaminski]

Ron, that is great! Thank you for the update. I'll have to give it a try.

[John Klayer]

Where does one buy sodium borohydride?

[jeff-blyth]

Hey Ron, what an interesting new twist you have made by bringing together techniques I discovered which were done over 30 years apart and I never would have thought of bringing them together.

I thought of the chemical blackening technique as a
curiosity ---almost just a conversation piece of minor interest back in those heady days back in TJ ‘s 1985 Lake Forest symposium. But now you have resurrected it for a good new purpose . It makes real sense to enable you to do a final color tweaking AFTER you have got your black backing in place.
It is really interesting that you can do that post- swelling trick straight through that blackened layer.
Well done Ron!
Jeff