Re: Gum problem(s)

Katharine,

I agree with what you write. Two quick comments.

I have see other books on light sensitive systems that contain some
information on dichromate colloids, but none of them are as useful as
Kosar. In writing "one of the standard reference texts" I was
thinking more in terms of light sensitive systems in general rather
than dichromate colloid processes. Sorry for the confusion.

Also, I agree with you about the errors. As I suggested (or implied)
in the original message, people who claim to find a lot of errors in
Kosar appear to expect that all of his observations should apply 100%
to gum printing, when in fact Kosar does not write specifically for
gum but for colloid processes in general. For example, everything
that applies to carbon does not apply to gum, and vice-versa.

Sandy

>On Nov 19, 2005, at 9:13 AM, Sandy King wrote:
>
>>Yves,
>>
>>There was quite a bit of scientific literature done on dichromate
>>colloid systems in the period from 1900-1960. One of the standard
>>reference texts on this subject is Light-Sensitive Systems by
>>Jaromir Kosar, specifically Chapter 2 on Dichromated Colloids.
>
>
>"One of the" suggests that there are other standard reference texts
>on dichromated colloids besides Kosar? If so, references please?
>
>>
>>You must read Kosar with the understanding that certain
>>observations may no apply equally to all colloid processes, which
>>has lead many
>> to suggest that the book is full of errors. On the whole I think
>>anyone interested in any of the dichromate based processes would
>>find Kosar interesting, and perhaps useful.
>
>Yves,
>I don't know who the "many" are who say that Kosar is full of
>errors; I only know of one. . As I leaf through my own copy, I only
>find my handscribble "Wrong!" in one place, where he says "The idea
>that the dichromate ion might act as a photosensitizer was first
>proposed by Galinsky on the grounds of observations made by
>Brintzinger and Maurer" and my objection was simply to the citation,
>not to the information that the dichromate ion might act as a
>photosensitizer. And the objection is miniscule against the
>information contained in the chapter. I certainly agree with Sandy
>that "anyone interested in dichromate based processes would find
>Kosar interesting, and perhaps useful."
>
>When you're done, you still won't know how the gum process works,
>because much of what (little) is now understood about the
>crosslinking has been learned since this book was published, but
>you'll have a lot of subinformation about how dichromated processes
>work, at least as applied to dichromated gelatin. The graph I
>mentioned to you, showing the relationship between humidity and
>exposure time in dichromated gelatin, is in that chapter, on page
>81. As I said, there is a similar graph for dichromated gum arabic
>that I got from another source, that I haven't dug out of the pile
>yet. In this case at least, dichromated gelatin and dichromated gum
>seem to behave similarly.
>
>When I first naively asked about the chemistry of the process on
>this list, assuming that there was a simple answer to the question,
>someone gave the Kosar reference, and someone else chimed back
>immediately and said I wouldn't find it useful, but when I found
>that Powells had a used copy, I got in the car and drove 3 hours,
>bought the book and read the chapter sitting on the curb before
>driving home again. It was worth it. Cheers,
>Katharine
Received on Sat Nov 19 15:23:45 2005