On the Toning of Cyanotypes

[Máx Arnold]

Yesterday night I tried with a strong pepper tea. It didn't work.
There was no toning, even when left a lot of time.
That kind of staining Frank says can occur, and normally does, but I'm trying to avoid it by washing the print after it gets toned. Paper base staining is a strong concern to me.

There should be some more interesting sources of polyphenols we haven't yet realised.

Max.

 

[fgorga]

Last evening I was toned another batch of cyanotypes. As a result I hive a correction to my original post and an update.

First the correction... the actual concentration of gallic acid I use for toning is 1% (w/v) not 2% (w/v) as originally stated. Gallic acid is not soluble at 2% (w/v). Even at 1% (w/v) there was a very small amount of solid remaining which I just ignored.

This "story" is a good example of why keeping good notes is useful. When I went to make up a second batch of gallic acid solution last evening, I just made 2% as it said on my bottle. Of course, it did not dissolve which sent me back to my notes which clearly say that the 2% was not soluble and that I had doubled the volume of water in order to dissolve all of the solid. So keep good notes and remember to relabel your bottle if you make a change!!!

The update... I have been using a stock of tannic acid powder that came from a scientific supplier (Fisher Scientific). This material is not labeled as to its grade but it is a very light tan powder which dissolves to make a light yellow solution. Nearing the end of this supply, I purchased some more tannic acid from Bostick & Sullivan. This material is a much darker reddish brown and when dissolved makes a solution whose color is reminiscent of a cola soft drink. The new tannic acid works just fine for toning cyanotypes.

Last evening, I was toning using the combination of tannic acid and ammonia and the new tannic acid gave a very slightly different tone (a bit more red) than the older material but it works just fine... as expected.

 

[nmp]

Yesterday night I tried with a strong pepper tea. It didn't work.
There was no toning, even when left a lot of time.
That kind of staining Frank says can occur, and normally does, but I'm trying to avoid it by washing the print after it gets toned. Paper base staining is a strong concern to me.

There should be some more interesting sources of polyphenols we haven't yet realised.

Max.

There is quite a bit of tannic acid in oak acorns too. That is what makes them bitter and inedible as is. Last fall I picked up a few from the neighborhood tree and boiled them (after removing the shells) as recommended to remove the tannins except that I kept the liquid. It did tone a cyanotype print in a quick test. However, boiling also leached some oil-like material that stained/gunked up the paper as well. I need to figure put how to purify the liquid. If it can be easily done, this might be another nice free alternative.

Experiments, experiments....

:Niranjan.

 

[Andrew O'Neill]

"This material is a much darker reddish brown and when dissolved makes a solution whose color is reminiscent of a cola soft drink"

That describes perfectly the stuff that I got from the wine making supply shop.

 

[Máx Arnold]

Boiling acorns or bark is the way to go when looking for tannins.

Linden tea didn't produce good results... testing, testing...
(I brewed linden tea instead of green tea because I got confused)

 

[Andrew O'Neill]

Boiling acorns or bark is the way to go when looking for tannins.

Linden tea didn't produce good results... testing, testing...
(I brewed linden tea instead of green tea because I got confused)

Millions of acorns on the ground in the greenbelt behind my house in Autumn. I'll have to try this.

 

[grahamp]

I have had some interesting results with wine tannin (chestnut in my case) on commercial cyanotype paper. http://grahamp.dotinthelandscape.org/cyanotype.html
Now I have some free time (!) I should assemble my UVA/UVB meter. I have the components, so I just have to put together the software for the Raspberry Pi.