My initial tests with Diazidostilbene (DAS) sensitiser have been consistent. Working with the same negative given same exposure and processing technique my time trial of 7, 14 , 28 and finally 60 days gave exactly the same result in terms of exposure and contrast.
I have made several more batches experimenting with 0.3% to 0.7% concentrations and more recently explored new pigments including Sumi ink and iron oxide black. Again the DAS performs consistently well.
I store the paper an old bromide paper box inside black plastic bag and thats it. I have noticed with stronger concentrations of DAS sensitiser ie 0.5% and greater there is a yellow stain which is more apparent when using cotton rag papers. This can be cleared, but I am still waiting to test clearing formula using metabisulphate and potassium permanganate.
Alternative Process by David Chalmers 
April 18th, 2014 at 3:05 am
Nice work. I am not unfamiliar with carbon. Used to work with UltraStable and I still have some.
DAS – have you found the best amount of DAS 0.5% or so.
How do you clear the stain? Same formula as for UltraStable? I also made own black tissues using Sumi ink.
Now I have a 4 colour set of sumi – got it from my Japanese students.
May 27th, 2014 at 11:23 am
Hello Stig
Thank you for your kind comment regarding my work. DAS is generally used at 0.5% but I have worked with 0.3% and 0.7% with successful results.
Clearing consists of a two part formula using very weak potassium permanganate in sodium chloride and sodium meta-bisulfite and sodium sulfite.
Sumi ink is beautifully rich with neutral tone. Kremer Iron oxide pigment diluted with glycerin gives similar results. My personal favourite is Windsor and Newton Indian ink.
Please keep in touch and let me know if you try carbon?!
David
August 19th, 2014 at 3:04 pm
You said : Sumi ink is beautifully rich with neutral tone. Kremer Iron oxide pigment diluted with glycerin gives similar results. My personal favourite is Windsor and Newton Indian ink.
Have You measured the cmyk- components?
I am looking for a pigment that’s dead on neutral like the black tissue in UltraStable.
(C=M=Y=K). We have tried Kremer PBk7 but it is not neutral – it is very warm.
How much of W+N Indian Ink are You using?
I need a neutral black for color printing.
Regards
Stig
November 19th, 2014 at 12:23 am
I think that W&N indian ink is superb with excellwnt neutral density.
Its my overal favourite ans also the very first ink i choose 22 years ago when i started experimenting with carbon.
I like sumi because it is also very rich and is derived from pine charcoal which some hiw apwals to my tree images