Peter Marshall wrote:
>a) I can see no health and safety grounds for not using 1% sulphuric acid.
>This must be one of the safest chemicals we handle in alt-photo!
>I agree with you 100% regarding a 1% solution, but was thinking more of the
health and safety problems that might occur in handling the concentrated
acid while diluting it. I've had rubber gloves leak, even when I'm doing the
right thing, to say nothing of the times I've absent mindedly done something
stupid. Apologies to Pete Frederick if this seems like "nannifying"<,
>but if there is a safer (preferably slightly alkaline) alternative that
performs just as well, it would be preferable.<
I could not agree more, I am not into S&M well not with chemicals anyway :-)
>Maybe it's worth asking about the pH of 5% sodium metabisulfite and how it
compares to 1% sulphuric acid? Maybe a slightly stronger sodium
metabisulfite<
The problem with sod metabisulfite is that you get a bright greeny blue colour
to the cleared sample it is light in tonal value but could course problems
in multi colour work .I am going to retest the sulphite when I get some of
your sodd dithionite. also your brilliant suggestion, hypo ! why not it is
a sulphur compound
.
>My faded dichromate image was probably produced in the
late 1970s (I was
still a schoolboy, albeit in high school), <
And I was teaching my first gum workshop helping out Professor
Margaret,Harker Hon FRPS Hon FIBP as technical backup when she was giving
her Linked Ring lectures to the University of Westminster.I must have some
of my reference notes there may even be a print to compare.
>We'll all be interested to hear how your more systematic tests go, Pete. Its
>probably just a matter of keeping notes of your reflection density readings,
>labelling and dividing each test strip, putting half in a sunny spot, and
>keeping the other half in the dark.<
This is exactly what I am going to do Philip
Thank you for your contribution
pete