From: Joe Smigiel (jsmigiel@kvcc.edu)
Date: 07/24/03-12:39:47 PM Z
I guess I'm missing something here in the discussion. The point seems to be about the viscosity of the gum emulsion with some advocating using powdered dichromate and mixing it directly into a pigmented gum solution with a bit of water thrown in if I'm following correctly.
I would agree with the assertion that a more viscous emulsion stains less, is harder to spread evenly with a brush, etc. What I don't get is why keeping a saturated (or several strengths) bottle of dichromate around and diluting that to desired concentration is seen as less desirable. Keeping the dichromate in solution and mixing it from the dry state once minimizes inhalation hazards as well as the oxidation hazard of the chemical. I presume you can't boost the concentration higher than its saturation value in water by mixing it directly with the dichromated gum so what benefit is there in using it dry? Just use less of the saturated solution and more gum + pigment if you wish to alter the viscosity or dichromate concentration in the final emulsion. Am I missing something here???
I really wish I could have been at APIS to hear Stuart's talk and meeting a bunch of people from the list, but a recent health emergency prevented me from attending (as well as doing much else this summer). I did send a spy though who enjoyed the programs very much and took notes for me. She had very positive things to say about Stuart's work as was very taken by Sam Wang's prints and Zoe's albumens.
Oh well, maybe I can make it in 2005...
Joe
>>> kthayer@pacifier.com 07/24/03 09:07 AM >>>
Clay wrote:
>
. By
> adding dry dichromate to the gum directly, you can greatly reduce the
> total amount of water in the mix, and increase its viscosity, which can
> lead to some extremely smooth coatings. This may not be something
> desirable for everyone - I don't know.
What you seem to be suggesting here is that smooth coatings are
available only to people using less water, and that only those not
caring about smooth coating would use more water, which is a false
assumption on both counts. Dave Rose, I believe has told us that he uses
both saturated ammonium and saturated potassium dichromates; a look at
his straight gum prints should disabuse a person of the notion that one
can't get smooth coatings using saturated dichromate in solution. (Sorry
to keep using you as an example, Dave, but you're such a good example of
the ideas I'm trying to get across.)
Katharine Thayer
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