From: Katharine Thayer (kthayer@pacifier.com)
Date: 07/23/03-03:06:02 PM Z
Sandy King wrote:
>
> Kathrine Thayer wrote:
>
> >Sandy looked at the amount
> >of dichromate in relation to the amount of gum and called it 20% and
> >said that was less than saturated ammonium dichromate and asked why are
> >so many gum printers using more dichromate than is necessary?
>
> Not exactly. I assumed, and so stated in the message to which you
> allude, that the addition of pigment (assuming pigment in liquid
> dispersion, though not specified) would reduce slightly the amount of
> dichromate in relation to the total quantity of emulsion to less than
> 20% The 16% solution that you derive is very close to what I would
> have predicted.
> .
>
> Do you not figure the amount of pigment in the calculation.
>
No, we don't; I got the 16% by adding the water, not by adding the
pigment. Your earlier question "So why are folks using saturated
solutions of ammonium dichromate if it is not necessary?" implied that
you thought Stuart and Sam and others using this dry dichromate method
were using less actual dichromate than someone doing gum the traditional
way, and I think I showed, (knock on wood my calculations were right)
that it's not necessarily so.
kt
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