Direct tannin process (no bleaching, no Potassium ferricyanide, just ferric oxalate/water and hydrogen peroxide + tannins)

[Raghu Kuvempunagar]

They may be but to what end is not clear to me.

:Niranjan.

In the case of Catechol toner, adding Peroxide to it makes it produce more dye/stain.

 

[nmp]

Oh yes, I think so. I was imagining mixing and using immediately. The question would be whether the oxalate reaction would happen or whether all the peroxide would be used up in other reactions. I've been playing with botanical cyanotype toners and with some of them you can visually see the liquid change color when exposed just to air. Annette Golaz says that higher pH promotes oxidation in the toners, so plays more of a role than just converting prussian blue.

Yeah, in alkaline medium, tannic acid gets de-protonated (-OH to O- and H+) making it more prone to oxidation, changing color. It also tones faster and as I have noticed, tends to stain the paper more as well. So it's better to keep it neutral to slightly acidic.

:Niranjan

 

[Raghu Kuvempunagar]

My first attempt didn't go well but the mistake is mine only. I underestimated the exposure thinking it would be very short like Cyanotype Rex. I'll try again sometime later with generously more exposure.