Ewesly / Holographic Formulae / Kodak R-9

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Bleach solution

9.5 g Potassium Dichromate
8 mL Sulfuric Acid (or 24 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.

This was Kodak's bleach for reversal processing of direct positive black and white transparency or movie films.

Shelf life: This solution stores indefinitely, should be dumped when it takes longer than a couple of minutes to clear.

Source: <a href="ReversalBleaching.PDF" title="Predates Pyrochrome" target="_new">R. L. Lamberts and C. N. Kurtz, "Reversal Bleaching for Low Flare Light In Holograms", Applied Optics 10, 1342 (1971</a>)