Simultaneous bleaching and toning for cyanotypes?

[Alienguru]

Has anyone tried it? I mean putting a cyanotype print in a mixture of tea and... let's say sodium bicarbonate (baking soda) - AFAIK it's the most easily accessable cyanotype bleach

[2F/2F]

My guess is that it would work, and you'd get a purple tone with dingy highlights. I guess that because when I purple tone cyanotypes, I go back and forth between sodium carbonate solution and tannic acid solution or black tea. When I do this, it is quite a sloppy affair, yet it doesn't seem to matter if there is any contamination or not.

That being said, if you go far enough with tea toning, you do get a similar purple anyhow. It just takes a lot longer.

[Alienguru]

So it would be better to do both processes separately?

[Matthew Rusbarsky]

I think you are confusing baking soda with washing soda. Washing soda is a good bleach for cyano, baking soda less so.

[jnanian]

you could take your baking soda, and bake it at a low temp
to force the water out of it, and "convert" it to washing soda

the my favorite way to bleach back cyanotypes is weak washing soda
in water, and a paint brush. if i leave it in a bath, it takes too long,
or goes to fast, so i use a paint brush and then a water bath to rinse ...


have fun !
john

[Loris Medici]

John,

If subjected to acidic conditions, the alkali bleached cyanotype may regain some density. (The alkali bleaching action is - to some extent - reversible...) In other words, that bleaching methor is not "permanent", therefore, beware!

If you want to bleach the cyanotype permanently, you can use a relatively strong (20% IIRC...) solution of oxalic acid.

Regards,
Loris.

[Alienguru]

I think you are confusing baking soda with washing soda. Washing soda is a good bleach for cyano, baking soda less so.

Thanx, but I still know the difference between bicarbonate and carbonate. And believe me, where I live washing soda is not very popular, so baking soda is much more easily affordable.

John, it sounds like fun, I'll give it a try.

My whole idea was to reduce the bleaching/tonning process to a single bath. I suppose that the tonning will take place simultaneously with the bleaching.