[alt-photo] DAS - group buy
workshops at polychrome.nl
Mon Jan 21 20:45:03 GMT 2013
Chris Holmquist or "holmburgers" at APUG is organizing a group buy of DAS. DAS is the acronym for 4,4'-Diazidostilbene-2,2'-disulfonic acid, disodium salt, tetrahydrate
DAS is a non toxic replacement for dichromates and was also the sensitizer in the legendary Ultrastable pigment papers. I have been working with DAS for almost two years now and am very happy with the results. My first batch I bought at my local chemical supplier in the Netherlands and a second 1kg order directly from a Shanghai manufacturer in China. This group buy comes from a relatively old batch from Secant in the US. It has been stored refridgerated at Secant and was tested and approved by Tod Gangler of http://www.colorcarbonprint.com/. The prize is very competitive!
DAS can be incorporated in the carbon pigment paper and has no dark effect. This speeds up working considerably as the pigment paper is presensitized allready.
I have tested the chemical with several other colloïds. It does not work with Gum arabic. With caseïn though it is a perfect match. Also with some synthetic colloids results are very good. With casein exposure times can be cut down considerably, same with the synthetic colloïds.
This group buy might be a nice occasion to do some testing. A good starting dilution is 3%. For carbon a Gelatin/DAS ratio of 0.06 is a good starting point. This means that for 1 liter 10% gelatin one needs 6 grams DAS.
Kees | zerochrome.org (coming soon)
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