> I did not use sod sulphite as I have previously tested sulphite against
> metabisulhite and found them very similar, nor have I tested hypo clearing
> agent, or Philip Jackson's sodium dithionite, I would like any further
> suggestions from other members of the list as I intend to test them all.
>
> I have built a fume cupboard around my photographic processing sink and do
> all my pongy chemical mixing in there.
>
But if we're talking for the world at large, which may not have a built-in
fume cupboard, and can buy HCA and/or sodium sulfite with their regular
supplies, while perhaps not so easily getting bisulfite, or sulfuric acid,
I would tend to think in terms of HCA,etc. -- especially since you say you
"found them very similar."
Philip (or someone) posted some awful warnings against sodium dithionite
last year, as I recall, and that might be still harder to get. So unless
it has some wonderful virtue (such as removing wrinkles) it seems
unappealing.
> >3. Some people would be antsy handling (or even getting) sulphuric acid.
> (And it isn't clear to me that it has any advantage except in gross
> over-exposure.)<
>
> This is perfectly understandable, but as you have said on a number of
> occasions that there are a lot of very nasty things in the kitchen cupboard
that line about the kitchen cupboard is Terry's
> and a 1% sol is very weak.I can give you three main advantages to the use
> of this clearing agent :-
>
> 1) It is the strongest agent
>
> 2) It is the fastest average time in fresh solution 30sec's to 2min's
>
> 3) It will get the stain down to almost base white on paper and actual base
> white on Synteape or any other impervious substrate
All other things being equal, the 1% sulfuric sounds good -- no powder to
mix, as well. I would still want to give it a pH check on completion.
And for what it's worth, I mention again what has been for me a handy
method of dealing with such acids, especially sulfuric: I go into crisis
room with plastic apron, good gloves, a safety litre of water and as many
wits about me as possible (ie not in rush or distract mode) and make a 10%
"stock" solution which I then work from.
> Fotempera process.It is a totally consistent process, it works exactly the
> same time after time.
> In 1994 I was invited to take part in a symposium with
> David Sopick,and John Pollard at RMIT in Melbourne Australia, we staged a
> group exhibition of our work, took part in a public forum, also ran
> concurrent workshops over three days,at the end of which we had a
> throughput 36 students,all the students who worked with me achieved
> finished work whereas only a few managed to produce finished work in David
> And Johns classes,, both John and David were working the classic gum
> processes whereas I was employing the Fotempera, both my friends David and
> John are talented artists, experienced teachers, and skilled practitioners.
> it was the process that made the difference.
Peter, you may simply have proved that Scopick & Pollard are not very good
teachers... Of course the Fotempera process, which I haven't tried, may be
as consistent as el nino, but (I don't want to tread on all 20 toes at
once, but you oblige me) aside from the teaching methods, I don't think
the gum methods of your friends are, um, exemplary. I read John Pollard's
"working" method in an English magazine & it curled my hair. Scopick I
have addressed on this list enough to invite a lawsuit. However, as I have
told you before, I teach non-photographers (orthodontists, librarians,
actuaries, even *undergraduates*) to do gum printing in a morning or two.
The bright ones (or anyway the ones paying attention) do good gum prints
the first day.("Throughput" of more than 30 students, one teacher.)
There probably are more variables in gum printing than Fotempera (like
paper, for one thing, since I take it synetape is always the same), and our
not knowing all the variables can be (has been) booby trap, but all I
meant by that remark was that I didn't see the finding about the
dichromate stain in .1 density as "explanation" for any inexplicablenesses I
have run into.
Meanwhile, let us not forget to distinguish among dichromate stain,
pigment stain and chemical fog in gum printing -- each sui generis.
Judy