Friday , 17 November 2017

Toning Formulas for Cyanotype

Toning involves two basic steps: bleaching and toning. Every toner for this process contains some form of tannin, because cyanotype base formulas use iron instead of silver gelatin, like black-and-white photography. Tannin chemically binds to iron in the coated emulsion, changing the print’s color.

Why Tone Your Prints?

There will be times when you simply don’t want a blue image but still wish to use the cyanotype process because of its flexibility and simplicity. Below are formulas for changing the color of prints once they have completed the final wash.

In general, it is a good idea to overexpose your cyanotypes if you intend to tone them. Many of the following formulas utilize sodium carbonate or ammonia, which tend to radically reduce print density if the solutions are too strong.

General Requirements:

1.) Age your prints 24 hours for the emulsion to harden.

2.) Pre-wet print in distilled water (tap water is not recommended due to containments).

3.) Have multiple prints – you never know what you’re going to get.

4.) Leave print in toner for extended period – agitating periodically.

Bleaching Phase:

The purpose of bleaching is to break down iron in the cyanotype emulsion so tannin in the toner solution can bind easily. If your tap water is heavily chlorinated, you may be able to skip the bleaching process outlined below.

How much bleach really depends on your coating process and toning formula. Bleaching too much will decrease shadow density. Too little bleaching will adjust highlights while keeping shadow density the same.

Bleach types

The most common form of bleach solution is sodium carbonate. That’s Washing Soda, usually found in your grocery store’s cleaner aisle or a photo chemical supply store. Don’t confuse this with sodium bicarbonate (baking soda).

Another type of bleach includes household ammonia. Ammonia stinks, horribly, and usually produces a browner image.

Always rinse your print well in a bath of running water between bleaching and toning.

Toning Phase:

Some toners are more efficient and stain less than others; However, keep in mind that all toners will stain your paper base to some extent despite your best efforts.

Tea Toner

Make certain to use teas with tannin in them, like black or green – white, red, and most herbal teas don’t have enough tannin to affect your print. Tea toners work well with minimum bleaching and require a longer immersion for the iron to shift. Tone prints in tea for 2 – 8 hours. 

Green tea: Produces eggplant/black shadows and doesn’t stain the paper base too badly. If you’re toning a high key image, green tea will sometimes produce pink highlights. It can also split-tone images with thicker emulsions.

Black tea: Produces warm shades of black and brown nearly impossible to get anywhere else. Also used as split-toner for warm highlights and blue shadows.

Earl Grey: Avoid this. It has excessive oils that can damage your print.

Coffee Toner

Coffee toner doesn’t take as long as tea or stain the paper as badly; However, expect at least an hour of immersion. Let the print rest in a water bath before the final rinse.

Tannic Acid Toner

Tannic acid toning produces the closest thing to true black and has the widest tonal range. But the solution is highly reactive and sometimes inconsistent. Be mindful of how much bleaching is done beforehand.  

This toner produces the least paper staining. Mixed with distilled water, tannic acid toner will last for several weeks to months. Over time, mold can form on the surface. Just filter the solution before use.  When the solution turns dark brown or tiny granules appear, discard.

TONING FORMULA #1

Sodium Carbonate 1g Bleach Solution
Distilled Water 100ml
 
Tannic Acid 1g Toning Solution
Distilled Water 100ml

 

TONING FORMULA #2

Ammonium Hydroxide 5ml Bleach Solution
Distilled Water 100ml
 
Tannic Acid 1g Toning Solution
Distilled Water 100ml

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