I have poured several A4 and two A2 size sheets with 750ml glop sensitized with this magic 'hardener #3' (di-Sodium-4,4'-diazido-stilbene-2,2'-disulfonate tetrahydrate) I received last week. In this glop I mixed a dilution of the powder as Charles wrote above. So in this 750ml is 4,5 gr diazo salt.
While waiting for them to dry I couldn't resist to do some tests.
I diluted another 3 grams of the diazostilbene in 100ml water. And with this I tried:
1. A gum print
I mixed the 3% diazo 1+1 with my regular 14 baumé pigmented gum and tried several exposure times. None where succesful. The gum allways ran off the sheet leaving a yellow stained image in the paperbase.
2. A PVA print
Same setup but now I took a 10% solution of pigmented Mowiol 4-88, a partially hydrolized PVA. This worked a little better. There was some hardening at very long exposure times and a trace of an image was left.
So far so good. Probably the concentration of the diazo must be higher to make this work, at the same time rendering it unusable by it's cost.
I took one of my 'normal' pigment sheets and brush sensitized it with the 3% diazo solution. I exposed it, dried it overnight (!) and processed it as a normal carbon print, transfered to a sheet of fixed glossy RC paper.
It worked perpectly. Maybe the exposure time could have been a little bit longer, but it is pretty close to a normal printing time!
So I'm very happy with my investment in this powder!
I was allready used a to presensitized carbon because I used Halvor Bjørngård's Chiba method of ferric hardening. But that's more complicated because it is so sensitive to oxigen. I experimented with several temporary protective layers, other than the agar-agar Halvor describes.
More tests will follow.
Exciting stuff! You guys are doing really noble experimentation and ensuring that the carbon process will continue well into the 21st century when dichromates are unobtainable (assuming here), not to mention providing a safer and perhaps more convenient method.
Originally Posted by keesbran
I'm reading this thread in the hope that I can find a non dichromate sensitizer to use in my Gum Printing practice.
Have you had a chance to muck around any further with that sensitizer on gum prints?
Do you know of anyone else who is specifically looking to de-dichromate their gum printing?
No not yet, but I will do soon. But as I said with the diazostilbene it might be getting rather expensive.
Yes, Halvor Bjørngård describes a non toxic approach in his Chiba thesis about using ferric salts for carbon and gum printing. You can download it here: The Chiba System
Originally Posted by BenjaminAustin
Thanks for that article :) Very informative!
I'll have a go at some of those processes at some stage and post my results :)
One thing that was very useful in that pdf is the method he uses for affixing the paper to a substrate. (Gelatin on the paper, then glued down - releases in hot water. Genius!)
If you have any further luck using the diazo salts with the gum printing I'd love to hear...
Polyvinyl-alcohol is another colloid that can be used for making relief images I guess.
Here are 2 formulas, one for ammonium dichromate and the other for p-Diazo-diphenyl-amine-formaldehyde.
Just came across this and wanted to also see if anything's going on with diazo sensitizing lately...?
Not here. Too busy printing. Thanks for the link.
Probably worth a try...but I don't know enough about the stuff. Is this the same thing a lot of alt-printers use to size their paper? Do they not harden it?
Looks like they're recommending a combination of polyvinyl alcohol (PVA) and polyvinyl acetate (PVAc).
Yeah, I have no plans to try it myself... though it's interesting I guess to see a comparison of quanitities for ammonium bichromate & that diazo hardener. Like Charles said, they're quite close.
So what's the final word on where to get the proper diazo sensitizer in the US? And what's the cost?
I intend to make diazo carbon one of my goals while in Rochester, and I'm just thinking about getting a source. It's possible that we could get the formulary to stock it, and the price might be better. Who knows though...