Toning for protection

[piticu]

Could you fellow forum members suggest some toners for protecting cyanotypes and van dykes? I don't care about colors, only about the protection level they provide.
Thank you

 

[Loris Medici]

You don't need to tone cyanotype for protection, just keep it away from alkali materials + make sure the surface is in contact with oxygen (do not apply an impermeable coating) and that's all. It's one of the most stable alt-processes around...

OTOH, you definitely need to tone Vandyke for longevity. (Plus, pay a good deal of attention to the paper selection and washing/clearing steps during processing...) One of the best toner options for Vandyke is the gold-thiourea toner. Search the web for the exact formula.

Regards,
Loris.

 

[piticu]

if i don't tone the cyanotypes i make they fade overnight due to acid buffers from the paper. i don't have access to other papers so… you see… i have to tone cyanotypes and i was wondering if there's something else besides tannin.
i understood that ferous tanate is very very stable regarding oxidizing over time, maybe i will stick with tannin. i ordered some wine tannin from a guy in sweeden really cheap: less than 3e including shipping to romania for 50g.

 

[Loris Medici]

It's not the acid then, cyanotype actually likes acid environment. If your untoned cyanotypes are fading, then that's a good indication that your paper has calcium carbonate alkali buffer. In no condition you should attempt to print cyanotype on alkali surfaces!

If you can't obtain any other paper, then just neutralize the alkali paper (BEFORE PRINTING!) by putting it in a simple 2% hydrochloric acid neutralizing bath for at least 2 minutes (or until there's no more fizzing), changing the paper orientation halfway. Just rinse/wash well the paper later. (At least 30 minutes and 5 water changes.)

The image will be pretty stable on neutral (or acidic) paper. As a bonus, you'll notice a significant speed increase along with much higher image density.

BTW, I can get 0.5 to 1 kg (depending on the make/packaging) tannic acid here for that price. See winemakers in your area; they'll most certainly have it.

Hope this helps,
Loris.

 

[piticu]

It's not the acid then, cyanotype actually likes acid environment. If your untoned cyanotypes are fading, then that's a good indication that your paper has calcium carbonate alkali buffer. In no condition you should attempt to print cyanotype on alkali surfaces!

that's what i said my friend, acid buffers from the paper. of course it's some sort of calcium carbonate

that's a good advice about neutralizing the papers before coating. i didn't think about it although i believe i've read about it - it was oxalic acid instead of hydrocloric. i will try with azotic acid, i got around 100ml 60%.

in romania, tanic acid runs around 100e per 100g! it's insane!

 

[Loris Medici]

It's anti-acid buffer or more correctly (as I and everyone else - except you - use it) "alkali buffer"... See the literature; if you say "acid buffer" what others will understand is that the paper is acid (and buffered to remain acid), not alkali as in your case.

What is azotic acid? You're probably referring to nitric acid. Probably it's safer to use hydrochloric acid, this is usually present in ordinary household as calcium remover / wc cleaner. (15% max. strength, you'll just add it to some water to dilute...) 60% nitric acid is nasty; I'd stay away from it!

 

[piticu]

apologize for my bad language. you got it right, azotic acid means in my head HNO3 or nitric acid

 

[piticu]

it just hit me: i can also use citric acid, i got plenty of it. for sure i will try them both

 

[Loris Medici]

Unfortunately citric acid won't do the job: Citric acid + calcium carbonate = calcium citrate, and calcium citrate is highly insoluble, therefore won't leave the paper. Calcium chloride (hydrocholoric acid salt) or calcium nitrate (nitric acid salt) are highly soluble and will leave the paper.

P.S. Won't do the job cleanly I mean. Probably it will neutralize the buffer but will leave an alien reaction product in the paper, which is something we usually don't want.

 

[piticu]

thanks for helping me not wasting my time and chemicals

 

[piticu]

VDB in Moersch MT10 1:10 30s

 

[piticu]

VDB in Moersch MT1 1:400 30s

 

[Marco B]

Unfortunately citric acid won't do the job: Citric acid + calcium carbonate = calcium citrate, and calcium citrate is highly insoluble, therefore won't leave the paper. Calcium chloride (hydrocholoric acid salt) or calcium nitrate (nitric acid salt) are highly soluble and will leave the paper.

I am not a chemist (although I did get a fair amount of chemistry in my Biology study), but is this true?

The formation of calcium citrate seems to be governed or done mainly in the alkaline conditions using calcium hydroxide, instead of an acidic citrate solution? Calcium citrate does seem to be less soluble in water compared to many other compounds, still this Wikipedia article mentions it to be soluble in cold water.

And another important question:

And even if calcium citrate was formed and remains in the paper, is that still an issue for the cyanotype? Calciumcitrate is not calciumcarbonate, does it pose an issue for the Prussian blue pigment formed in a cyanotype?

Marco

 

[Loris Medici]

Marco, I didn't say it won't neutralize the buffer. In fact, there's this method of printing highly sensitive new cyanotype on otherwise unsuitable papers: You add 2 drops of 40% citric acid per ml of "coating solution" and the paper starts to work. (Because citric acid protects the cyanotype image from the detrimental effects of the paper's buffer.)

About the reaction: write the reaction formula for calcium carbonate + citric acid, if you like...

I don't think that the remaining calcium citrate will do bad for the cyanotype image; see the example above. OTOH, it's not a clean method (because of the irrelevant remainder compound in the paper) where there are much more suitable ones. (Such as acetic / hydrochloric acids. And we usually already have diluted hydrochloric acid in the cleaning closet - at least here in East Europe...) Besides, citric acid addition into the coating solution or the presence of citric acid in the paper will change the color of the cyanotype because you'll have citric acid embedded inside the prussian blue lattice. Do you see what I mean by "not clean"?

I think you must be kidding by defining 0.85g per liter as "soluble". (Maybe yes in academic sense, but definitely not in practical sense...) See the solubility figures for calcium acetate or calcium chloride, you'll get what I mean...

Regards,
Loris.

 

[piticu]

Classic formula cyanotype bleached in sodium carbonate and toned in wine tannin

 

[Loris Medici]

Great piticu! Have you managed to find tannin (for a good price) from the winery? 1 dessert spoon per liter will be more than enough... (There's staining in the paper base indicating your toner solution is a little bit on the strong side.) Don't pour it; just filter and reuse. One liter goes a long way. Also it helps to do a weak (1 dessert spoon per liter) citric acid bath after the image has completely developed, but before the final rinse baths. This will eliminate all non-image iron from the surface, therefore you'll be able to get cleaner whites. (If not, tannin also tones the whites...)

Regards,
Loris.

 

[piticu]

I got 250g of wine tannin for 12euros, incl shipping to Romania.
I mixed 50g with 1l distilled water to make the stock toner. I use 25ml for 1l tap water for oneshot working solution.
Thanks for the acid bath tip, i'll try it next time.

 

[Loris Medici]

Nice method, OTOH I think you can use the working solution more than once. 250g will keep for a very long time...

Mind to mix the stock solution before using it; it tends to precipitate...