Ewesly / Holographic Formulae / Pyrochrome
4 g Potassium Dichromate
4mL Sulfuric Acid (or 12 g Sodium Bisulfate)
One litre water
Bleaching time:Time it takes to clear plus 15 seconds, not to exceed 2 minutes.
Temperature: 20C Agitation: Constant
Distilled water is recommended otherwise white scum may collect in the emulsion. First hologram in the bath may take a long time to clear. When clearing time exceeds two minutes the bath is becoming saturated with silver salts and needs to be replaced. Hanging the plate vertically in a tank or with emulsion side down in a tray during bleaching speeds the exit of the soluble silver salts from the emulsion.
Shelf life: This solution stores indefinitely, but should be dumped when it takes longer than a couple of minutes to clear. Ilford SP679C is a packaged, concentrated version of this bleach.
Source: Walter Spierings, "'Pyrochrome' Processing Yields Color-Controlled Results with Silver-Halide Materials", holosphere Volume 10, Numbers 7 and 8, p.1, (1981)
<a href="../Developers/PYROAB.pdf" title="A revolution in its day!" target="_new">My ramble on The Process</a>.