The allure of the cyanotype process often begins with its signature Prussian blue. It’s striking, historical, and deeply satisfying to create. But for many practitioners, the journey doesn’t end there. The desire to coax different hues from the cyanotype print leads inevitably to the fascinating world of toning. Moving beyond the blue opens up a vast palette, transforming the familiar into something entirely new, personal, and expressive. Advanced toning isn’t just about changing color; it’s about controlling mood, enhancing detail, and adding depth to your photographic or photogram work.
Mastering these techniques requires patience, experimentation, and an understanding of the chemistry involved, however basic. It’s less about rigid formulas and more about developing an intuition for how different substances interact with the iron compounds embedded in the paper fibers. Forget the idea of simply dipping a print and getting a perfect sepia every time; advanced toning is a nuanced dance between bleaching, toning agents, timing, and the unique characteristics of your print and paper.
Understanding the Toning Process at its Core
At its heart, toning a cyanotype involves chemically altering or replacing the Prussian blue (ferric ferrocyanide) pigment. This usually happens in one or two steps. Often, the first step is bleaching. This involves using an alkaline solution (like washing soda, sodium carbonate, or ammonia) to break down the blue pigment, leaving behind a faint, often yellowish or pale brown image composed of ferric hydroxide. This bleached state is more receptive to certain toning agents.
The second step is the actual toning bath. Here, the print is immersed in a solution containing chemicals that react with the remaining iron compounds (either the original Prussian blue if not bleached, or the ferric hydroxide if bleached). These reactions form new, differently colored compounds. The most common toning agents are derived from plants, rich in tannins or other phenolic compounds, but specific chemicals can also be used for particular effects.
Preparing Prints for Successful Toning
Before you even think about toning, ensure your cyanotype print is optimally prepared. A well-exposed and thoroughly washed print is crucial. Residual cyanotype chemistry can interfere with the toning process, leading to uneven results or staining. Prints should be washed until the wash water runs completely clear, removing all unexposed sensitizer. It’s generally recommended to tone prints after they have been washed and dried completely, though some experiment with toning wet prints straight from the wash. A fully dried print often provides a more consistent starting point.
Verified Tip: Always start with a well-washed and preferably dried cyanotype. Residual sensitizer chemicals are a primary cause of uneven toning and unwanted stains. Ensure your highlights are clear and your blues are deep before considering toning.
Key Toning Agents and Techniques
The real excitement lies in the variety of toners available. While commercial kits exist, many advanced practitioners prefer mixing their own from basic chemicals or natural ingredients, allowing for greater control and unique outcomes.
Tannic Acid: The Versatile Toner
Tannic acid, often purchased as a powder, is a cornerstone of cyanotype toning. Depending on concentration, temperature, time, and whether the print was bleached first, it can yield a range of colors:
- Browns and Sephias: Achieved typically by bleaching the print first in a sodium carbonate solution, washing briefly, and then immersing in a warm tannic acid bath (e.g., 1-5 grams per liter of warm water).
- Purples and Aubergines: Often result from toning an unbleached print directly in a tannic acid solution. The blue mixes with the forming brown/tan.
- Deep Grays and Blacks: Can be achieved with stronger tannic acid solutions, longer immersion times, or sometimes by following the tannic acid bath with a brief dip back into an alkaline solution (like sodium carbonate), which can shift the color darker.
Natural Sources of Tannins: Don’t overlook everyday sources! Strong black tea, green tea (gives different, often grayer tones), coffee grounds (brewed strong), and even red wine (use cheap, tannin-rich varieties) can be used as effective toners. Each brings its own subtle variations in color and requires experimentation. Tea toning, for instance, is very popular for achieving classic brown tones, often after a bleach.
Sodium Carbonate: More Than Just a Bleach
Sodium Carbonate (washing soda) is primarily used as a bleaching agent. A weak solution (e.g., 1-2 teaspoons per liter of water) will gently fade the Prussian blue. The extent of bleaching dramatically impacts the final toned color. A partial bleach followed by toning can create beautiful split tones, where some blue remains alongside the new color. However, sodium carbonate can also act as a modifier *after* certain toners. A quick dip in a weak alkaline bath post-tannin toning can sometimes shift browns towards deeper blacks or purples.
Important Safety Note: While many common toning agents like tea or coffee are safe, chemicals like sodium carbonate, tannic acid powder, gallic acid, and especially pyrogallic acid require careful handling. Always work in a well-ventilated area, wear gloves and eye protection, and avoid inhaling dust or fumes. Label all containers clearly and dispose of chemicals responsibly according to local regulations.
Gallic Acid and Pyrogallic Acid: For Deeper Tones
Gallic acid and pyrogallic acid are related phenolic compounds often used after bleaching to achieve different shades, typically ranging from warm grays to deep blacks or rich warm browns.
- Gallic Acid: Often produces cooler grays and blacks compared to pyrogallic acid. It’s typically used in a weak solution (similar concentration to tannic acid) after a thorough bleach.
- Pyrogallic Acid (Pyro): Known for yielding warm, rich brown tones, sometimes leaning towards reddish-brown. Pyro is more potent and requires extra caution in handling. It’s often used in very dilute solutions after bleaching.
Both require experimentation with concentration and time to achieve the desired effect. They react sensitively to the amount of iron left after bleaching.
Exploring Botanical Toners
Beyond the common tannins, a vast world of botanical toning awaits the adventurous cyanotypist. Many plants contain compounds that can react with the iron in cyanotypes. This is highly experimental territory:
- Oak Galls: A traditional source of tannins, producing strong grays and blacks.
- Walnut Husks: Yield deep browns.
- Certain Flowers/Berries: Hibiscus, elderberry, etc., might produce subtle shifts (often purplish or reddish tints), though results can be unpredictable and may affect permanence.
Success here depends heavily on the specific plant, preparation method (infusion, decoction), concentration, and the print itself. Keep detailed notes!
Factors That Influence Your Final Color
Achieving consistent or desired tones requires understanding the variables at play:
- Paper Choice: Different papers absorb chemicals differently and have varying textures and buffering capacities, all affecting the final tone. Cotton rag papers generally tone well.
- Water Quality: Hard water with high mineral content can sometimes interfere with bleaching or toning. Using distilled or filtered water can provide more consistency.
- Toner Concentration: Stronger solutions generally work faster and produce deeper tones, but can sometimes stain highlights or obscure detail.
- Temperature: Warm toning baths typically accelerate the reaction, often leading to warmer or deeper colors compared to cold baths.
- Immersion Time: Longer times usually mean deeper toning, but watch closely! Toning can sometimes be reversed slightly with washing, but over-toning is hard to correct.
- Bleaching Level: The degree to which the blue is removed before toning is perhaps the most critical factor determining the final hue when using bleach-then-tone methods.
- Washing: Thorough washing between steps (e.g., after bleaching, before toning, and after toning) is essential to prevent contamination and ensure archival stability.
Troubleshooting Common Toning Issues
- Uneven Toning: Often caused by insufficient washing before toning, uneven bleaching, air bubbles clinging to the print surface during toning, or agitation issues. Ensure full immersion and gentle, consistent agitation.
- Loss of Detail/Highlight Staining: Can occur with overly strong bleach or toner solutions, or excessive toning times. Try diluting your solutions or reducing the time.
- Weak or No Toning: May result from inactive toner (old solutions), insufficient bleaching (if required), very short toning times, or unsuitable paper.
- Color Shifts During Drying: Toned prints can sometimes change color slightly as they dry. Always judge the final color once the print is fully dry.
Embrace the Experiment
Advanced cyanotype toning is as much an art as it is a science. While understanding the basic principles provides a foundation, the most exciting results often come from controlled experimentation. Keep meticulous notes on your process: paper type, exposure details, bleach concentration and time, toner recipe, temperature, toning time, and washing procedures. Build your own reference library of test strips. Don’t be afraid to try unconventional materials (responsibly, of course) or combine techniques like split toning or multiple toning baths. The journey beyond blue is rich with potential, waiting for you to explore and make your mark.
