Phosphoric acid was not one of the better options. Kodak HCA, Bostick &
Sullivan EDTA (there are a few different forms of EDTA), and Sodium Sulfite
were the best for me. Seeing as HCA is mainly Sodium Sulfite (at a rather
high price), I settled on three bathes each 50/50 EDTA and Sodium Sulfite
(one heaping teaspoon each per liter of water). This is a little cheaper
than using strait EDTA (sorry Richard!) and is slightly better (for me,
your mileage may vary). I suspect it is a bit less dangerous than the
acids, to you and your paper.
One odd note: the rinse step between developing and clearing is a BIG deal.
I think Kerik pointed this out in the previous thread. A good 5 minute
(minimum, I now use 10 minutes) rinse with moderate agitation will do
WONDERS for your clearing!
As for your getting tone in a final EDTA bath after your phosphoric acid
baths, could this be a reaction between these chemicals?? Have you tried
simply pouring a bit of the phosphic into the EDTA and seeing if there is a
reaction (I'm just guessing here)?
I wonder if water supply doesn't affect clearing? Minerals in the water
might make for different results. Of course, a differant paper or
developer might also change results. The testing is easy, give it a try.
tomf2468@pipeline.com (Tom Ferguson)
SRH@StephenHarrison.com (Stephen R Harrison) wrote:
>I typically use 5 clearing baths of phosphoric acid 3% sol'n five
>minutes per bath for 50/50 pt/Pd prints to clear Bienfang 360, and
>platinotype paper( Not Platine !)
<SNIP>
> (1) What about the use several types of clearing agents such as two
>baths of Phosphoric Acid 3% followed by one of EDTA followed by say Kodak
>hypo clearing agent. <SNIP>
> (2) As I understand it , the Kodak hypo clear opens up the fibers
>of the paper. Should that agent not be used first<SNIP>
> (3) What about combining different agents such as a combined 50/50
>bath of phosphoric acid (3%) and Kodak hypo clear .
> (4) Any comments re the relative effectiveness of citric acid vs
>phosphoris acid ?
> (5) I very definitely have trouble using only EDTA as a clearing
>agent <SNIP>