[Alt-photo] Re: DAS

[Kees Brandenburg]

Sigma-Aldridge is indeed selling it at crazy prizes. These small quantities are meant for lab testing. We need more industrial sources. In the past DAS was used as an ingredient for printing fluorescent sceens on the inside of cathode ray (tv) monitors. It's allways interesting to keep an eye on (obsolete) high tech procedures. The printing of micro stuctures on silicium wafers is also still a photo lithographic process too for example!

I have bought my first 250 grams of DAS here in the Netherlands at about € 1,15  per gram. I also have imported it directly from China, which was somewhat adventurous but I got it at about € 0,40 per gram, shipping included. The group buy was a little cheaper than that, but it was a (now sold out) rest of an older batch Secant (secantchemicals.com) carried.This is the same source Tod Gangler uses as ingredient for his color carbon printing as far as I know.  It is unshure if there will be new batches at Secant in the future. Who manufactures it for Secant is unclear. That's why I tried the Chinese.

What I should say is that DAS has also a 'staining problem'. This is hardly visible when doing double transfer carbon, because the temporary support (polyester or vinyl) doesn't hold the stain. That's different with direct transfer carbon and, to some extent, casein. The original Ultrastable (also DAS pre-sensitized) clearing recipe uses a (very) dilute potassium permanganate solution followed by a sulfite bath. This reintroduces toxicity and a strong oxidizer, with the permanganate. I would be very intersted to find alternative, and cleaner clearing options!

regards,

Kees


On 16 apr. 2013, at 09:16, Loris Medici <mail at loris.medici.name> wrote:

> Thank you much for the info Kees - much appreciated. The only source I
> can buy is thru Sigma-Adrich, and the have a ~EUR 55 price tag per
> 10g; absolutely prohibitive! (I can buy kg's of gelatin, pigment,
> dichromate and acetone or alcohol for a song here in Turkey...)
> 
> Regards,
> Loris.