From: Hamish Stewart (hamish@gumphoto.fsnet.co.uk)
Date: 02/23/03-05:30:49 PM Z
On 23/2/03 22:17, "Christina Z. Anderson" <zphoto@montana.net> wrote:
> Hi List,
> My usual barrage of questions for the week--but hey, at least I post my
> test results, too, huh?
>
> Gum questions:
> 1. Which colors absolutely do not work? I have these notes: hooker's
> green (washes out), emerald green, and any chromium based colors. I've loved
> the quinacridones in the past...moonglow by D Smith seemed to wash out quite
> a bit but could've mixed it up wrong. Do all whites work OK and has anyone
> tried a white on a dark paper?
I have used emerald green, though I understand it can react with other
colours, and I have avoided chrome colours as apparently they can react with
the dichromate. My current pigments work extremely well and I have broadly
followed the manufacturers permanence ratings which work well for me.
> 2. Do you use am di or pot di? I learned on am di and am wondering if it
> is worth it to buy some pot di. Webb/Reed say only use am di if you can't
> get pot di. Hirsch says use am di. Go figure. I just want to know what
> you guys use, and I do have the notes from the past about am di being lower
> contrast/muddier but then those saying that isn't the case. Does it boil
> down to what you are used to?
I used am di for years and recently switched to pot di. I prefer the pot di.
Like you I learnt on am di but was convinced to try something different. I
do find the pot di has a bit more contrast and is slower but I find it
clears better - and I am not talking about the stain but the sense that the
colours are cleaner rather than having a faint sense of a colour shift from
the amm di I am sure others with disagree with me on this one.
> 2a. If you diluted am di to the same percent as pot di would it be
> equivalent in speed?
I do not know enough about chemistry to answer that one
> 3. What clearing agent do you use? I have come across sodium sulfite,
> sodium bisulfite/metabisulfite, potassium bisulfite, and sulfuric acid 1%
> solution. Does sodium sulfite truly do the trick so I don't have to choke?
> the metabi literally gives me instant asthma.
Potassium bisulfite - yes strong fumes, you need appropriate protection and
one of the benefits of pot di is this part of the process will be shorter
:-)
> 4. Has anyone used lemon juice in the sensitizer to insolubilize it,
> decreasing exposure and giving better midtones? (Demachy, Photo-Aquatint,
> p. 39).
Sounds interesting but I haven't tried it - though I find that the hardest
element of gum printing is getting the shadows the way I want them - flat
negs seem to help. With my current light set up and negs I would prefer to
increase exposure times :-)
> 5. Dare I ask this, has Demachy's stain test been hashed out on this list
> already or is it worth mentioning? His book is from 1898, before Paul
> Anderson's 1911. Is it possible to talk this out civilly? If he has not
> been discussed, I can sum up his test and post it. Considering I've only
> been on the list 3 yr or so, you all could have been around this block
> before.
Have read about it but have never tried it. And I don't want to get into a
debate about it either. My thoughts were that without the sensitiser it
doesn't seem to make sense. If I have staining problems they are usually
related to a change with a paper I am working with - this happened recently
- very frustrating. Then you have to consider changes to the gum solution as
well. Ideally you would test each batch of gum and paper with every pigment
you use - I prefer to adjust when I see a change from my standard
pigment/gum dilutions.
> 6. How many gummists are there? I know Judy, Dave, Katherine, Joe, but who
> else isn't speaking up? Even part-timers?
So add one more to your list. You can look at my website which is very much
out of date - adding new images + content is on the agenda...
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Hamish Stewart - Gum Bichromate Photographer - visit
<http://www.gumphoto.fsnet.co.uk>
for gum bichromate images, technical information and links to recommended
resources on alternative photographic processes.
mailto:<hamish@gumphoto.fsnet.co.uk>
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