Re: Clearing Gum Bichromates

Pollmeier Klaus (100561.2417@compuserve.com)
12 Jan 96 15:29:29 EST

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Carson Graves wrote:
>Also, all of the chemicals so far discussed: alum, sodium bisulfite,
and sodium metabisulfite are hardeners. Would this treatment also be
beneficial to the gum emulsion (I have always assumed so) or do they
just harden gelatin?<

Be careful: the sodium bisulfite softens, not hardens the colloid coating and
makes the image very vulnerable during clearing! Additional hardening of gum
images is rather difficult to achieve and probably not necessary, because it is
almost insoluble after drying. And neither fungi, nor bacteriae like it from
then on...

Klaus Pollmeier

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