Re: Dichromate dilution and speed

Sandy King wrote:
>
> Katharine Thayer wrote:
>
> >
> >Obviously to compare my results to Sam's, and/or to answer your question
> >about how much DRY gum there is in the entire emulsion, would be
> >impossible since I don't know how much water there is in the gum; I
> >bought it mixed. But that's not what this comparison was about.
>
> You appear to have totally missed the point. That is exactly what the
> comparison is about. I made it clear in my initial response to Chris
> that the main reason to use dry dichromate in testing different
> percent solutions of dichromate was to establish control over the
> percentage of *actual gum* in the coating solution. By actual gum I
> don't mean the quantity of 14 Baume, but actual gum, the *colloid*
> itself, before it is diluted with anything. In case you missed it,
> Sam's method is based on mixing from scratch a gum solution from the
> real stuff, and that was our point of departure as best I recall?
>

Sorry, Sandy, this makes no sense to me. I can't see how using dry
dichromate has any bearing whatever on the percentage of "actual gum" in
the coating solution, or how the percentage of "actual gum" in the
coating solution has anything to do with the percentage of dichromate in
the coating solution. The gum I use is mixed directly from the real
stuff, just like Sam's. Perhaps the point of departure for the entire
discussion was Sam's method, but my point of departure was the statement
that low concentrations of dichromate do not necessitate longer exposure
times, and I made it clear that I was addressing only that question by
changing the subject line. I really don't get what you think I'm
missing. The answer to my question: does dichromate concentration affect
speed? is answered by holding everything constant but the dichromate
concentration, as I said, and which I did.
kt
Received on Sun Nov 30 21:54:37 2003