U of S | Mailing List Archive | alt-photo-process-l | Re: ferri sesquichlorati

Re: ferri sesquichlorati

On Oct 18, 2006, at 9:28 AM, Halvor Bjørngård wrote:

If you have Mike Wares Cyanotype book, have a look on the pellet process. It
contains gum, ferric and tartaric acid. It is mentioned somewhere in there
that Prussian blue can harden colloids, but have again not found any closer

If by "Prussian blue" you mean what I mean by Prussian blue, the pigment PB 27 (hydrous ferric ferrocyanide, or sometimes ferriammonium ferrocyanide) then it definitely doesn't harden gum arabic, because I use it for a pigment in the gum process all the time; it's become my favorite blue. Here's a test print made with Prussian blue. It's not a perfect print; there's something weird with the coating or the sizing in one corner that flawed the print, but you should be able to tell from the rest of the print that Prussian blue acts just like any other pigment in the gum process.


I'm working on a page about bitmaps where you can see a better example, but I'm not finished with that yet.
Katharine Thayer