[alt-photo] Re: gum contrast...

[Katharine Thayer]

Don't worry about thinking out loud, nothing wrong with that.   I was  
doing something of the same when I was trying to remember that old  
discussion which maybe only tangentially related, if at all.

Your question was what would be the difference between 1:1 gum/ 
dichromate with the dichromate dilution at 1x concentration and 2:1  
gum/dichromate with the dichromate dilution at 2x concentration, at  
the same exposure.  There should be no difference, because the amount  
of dichromate in the coating mix would be the same either way.   The  
statements on my website about different concentrations of dichromate  
assume that the gum/pigment is kept constant as the dichromate  
concentration is varied.  Hope that's helpful,
Katharine


On May 17, 2010, at 9:42 PM, Paul Viapiano wrote:

> Katherine and Loris...
>
> Please don't go through any big deal about this. I'm coming to  
> terms and re-examining the basic tenets here, and basically  
> thinking out loud about all this in theory. Of course, in gum,  
> practice is another thing.
>
> But all in all, just batting a few ideas around in my head. I  
> apologize to all about my constant stream here...someday I'll learn  
> to just sit back and enjoy this ;-)
>
> Paul
>
>
>
> ----- Original Message ----- From: "Katharine Thayer"  
> <kthayer at pacifier.com>
> To: "The alternative photographic processes mailing list" <alt- 
> photo-process-list at lists.altphotolist.org>
> Sent: Monday, May 17, 2010 9:21 PM
> Subject: [alt-photo] Re: gum contrast...
>
>
>
>> Paul, I am literally too tired to think tonight, but I have this   
>> vague idea that there was a discussion about this on the list a  
>> year  or two ago, and that I may even have done some testing.  I  
>> did a  quick search at the archives but didn't come up with what I  
>> was  looking for.  It seems like it wasn't exactly this question  
>> but was  masquerading as this question, or something like that,  
>> but I don't  remember the discussion exactly.  I'll look again in  
>> the morning.
>> kt
>>
>>
>> On May 17, 2010, at 4:00 PM, Paul Viapiano wrote:
>>
>>
>>> Hi all,
>>>
>>> Thanks for the comments on my last question. Sodium bisulfite   
>>> helped restore brighter colors but yes, not overexposing in the   
>>> first place is good advice.
>>>
>>> Riddle me this, sil vous plait: Knowing that decresing dichromate  
>>> increases contrast, what would be the difference between a  
>>> mixture  of 2:1 gum/dichromate and a mixture of 1:1 where the  
>>> dichromate is  1/2 strength, both at the same exposure time?
>>>
>>> Katherine mentions in her website that halving dichromate  
>>> reduces  speed by approx one stop. If you halved the dichromate,  
>>> and  increased the exposure by two, would you effectively get the  
>>> same  print as a 1:1? I'm trying to see relationships in theory  
>>> here...
>>>
>>> Thanks in advance...Paul
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>>
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