Ewesly / Holographic Formulae / CWPBQ2
15 g Citric Acid
50 g Potassium Bromide
2 g p-Benzoquinone (PBQ) added just before use.
One litre water
Bleaching time: One and a half times the time it takes to clear.
Temperature: 20C Agitation: Intermittent
Introduced with CWC2 developer. If you do not have good ventilation or a respirator, use one of the other rehalogenating formulas as the PBQ has a rather pungent odor. But if you take the proper precautions you will be rewarded.
Primary recommendation for bleaching the discontinued Agfa Holotest 8E56HD and 8E75HD films and plates. as there is no emulsion shrinkage, thanks to the tanning effect of the PBQ. Works well on Slavich PFG-01 plates and Fuji films. Also useful for processing Bulgarian Academy of Sciences HP-490 Holographic plates.
Shelf life: The acidified salt solution alone will last indefinitely; with PBQ added the bleach will need to be discarded at the end of the day. Keeping a lid on the developing tank or tray will extend the working life.
Source: D. J. Cooke and A. A. Ward, "Reflection-Hologram Processing for High Efficiency in Silver-Halide Emulsions," Applied Optics 23, 973 (1984).
Although I wrote <a href="../Developers/CWC2g.pdf" title="CWC2 Reigns Supreme! (Back then)" target="_new">this</a> a long time ago, I just recently illustrated it with examples of the test strips. The Agfa 8E75HD plates mentioned are long gone, but the developer is still used, and the descriptions of the process and the methodology of testing are still sound. It's a 14 page PDF, so it will take a while to download, but worth it. Some of the stuff mentioned in the footnotes might pop up on this site in the future.