----- Original Message -----
From: "Norman Baugher" <[EMAIL PROTECTED]>
> Also, if your stop bath is too old it likes to eat little holes in the
> emulsion. Been there, done that...
> Norm
>
It's not exhausted stop-bath that "eats" holes in emulsions, it's a
reaction between alkaline developer and acid fixer causing gas bubbles
to blast holes in the emulsion. The purpose of the stop-bath, apart
from the obvious one of stopping development, is to cause a gentle
neutralisation of developer alkalinity in an emulsion before the more
strongly acidic fixer comes into contact with it, also to prevent the
fixer itself from losing acidity due to carried over developer. If the
stop bath is exhausted then the alkali to acid reaction occurs in the
fixer, and if agitation is not adequate the bubbles will form and do
their damage. Of course if the stop bath is ~too~ acidic the reaction
will occur at that stage, so there's no point in making the stop-bath
stronger "just to be on the safe side".
Regards,
Anthony Farr
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