Anthocyanins: Exploring pH Indicators in Anthotype printing

Creating anthotype prints is a fascinating process that combines photography with botany. Let's take a look at the role of anthocyanins in anthotype printing.

One of the key ingredients for making these prints is anthocyanins, natural pigments responsible for the vibrant red, purple, and blue colors found in many fruits, vegetables, and flowers.

The Science Behind Anthotypes

Anthocyanins are more than just pigments; they are sensitive to the pH of their environment, which means their color can change dramatically depending on whether they are in an acidic or alkaline setting. This property makes them excellent pH indicators. For instance, in acidic conditions, anthocyanins tend to appear bright red, while in neutral to alkaline conditions, they shift to purple and then to blue.

Experimenting with Red Cabbage Emulsion

To illustrate this fascinating property, I conducted an experiment using red cabbage, a vegetable rich in anthocyanins. Here’s a detailed account of the process:

1. Extracting the Pigment: I began by simmering red cabbage in water. As the cabbage cooked, it released its pigment into the water, turning it a deep purplish color. This extraction process took time, allowing the cabbage to slowly infuse the water with its rich anthocyanins.
   

2. Changing the pH: Once the pigment was extracted, I experimented with various substances to alter the pH of the emulsion:

• Alcohol Vinegar: Adding vinegar, which is acidic, turned the emulsion a vibrant pink.

• Borax: This alkaline substance changed the emulsion to a greenish hue.

• Sodium Carbonate: Introducing sodium carbonate resulted in a greenish-yellow color.

• Lemon Juice: Adding lemon juice, another acidic agent, produced a pink shade with hints of purple.

Exposure and Results:

After adjusting the pH, I applied the emulsions to paper and exposed them to light. The results were stunning, demonstrating how the same red cabbage emulsion could yield a spectrum of colors depending on the pH.

Expanding Your Palette with Other pH Indicators anthocyanins in anthotype printing

Red cabbage isn't the only natural source of anthocyanins. Here are some other materials you can experiment with to create a variety of colors in your anthotype prints:

• Apple Skin: Known for its red and sometimes green hues.

• Red Onion Skin: Yields a range of reds and purples.

• Plums: Provide deep purples and blues.

• Poppies: Their vibrant petals can produce striking reds.

• Blueberries: Offer rich blues and purples.

• Cornflowers: Known for their bright blue color.

• Grapes: Depending on the variety, they can produce reds, purples, and blues.

Other pigments that aren't PH indicators

In addition to anthocyanins, there are other light-sensitive pigments used in alternative photographic processes that do not function as pH indicators. Chlorophyll, the green pigment found in plants, is one such example. Unlike anthocyanins, which change color based on pH, chlorophyll remains consistently green but is highly sensitive to light. This sensitivity allows it to be used in creating chlorophyll prints, where images are formed on leaves through a process called chlorophyll printing or leaf printing. Another example is carotenoids, which produce yellow, orange, and red colors in many fruits and vegetables. Carotenoids are stable in different pH environments and instead respond to light exposure, making them useful for creating vibrant prints that retain their color regardless of pH changes. These pigments expand the creative possibilities for artists exploring the intersection of photography and natural science.

Here's a list of all natural pigments (only anthocyanins are ph indicators):

1. Anthocyanins:

• Colors: Red, purple, blue.

• Sources: Red cabbage, berries, grapes, flowers.

• Characteristics: pH-sensitive, changing color from red in acidic conditions to blue in alkaline conditions.
  

1. Chlorophyll:

• Colors: Green.

• Sources: Leaves, algae, green vegetables.

• Characteristics: Light-sensitive, essential for photosynthesis.
  

1. Carotenoids:

• Colors: Yellow, orange, red.

• Sources: Carrots, tomatoes, bell peppers, corn, autumn leaves.

• Characteristics: Stable in various pH environments, quite light-sensitive.
  

1. Betalains:

• Colors: Red, yellow, purple.

• Sources: Beets, chard, prickly pear, some flowers.

• Characteristics: Water-soluble, stable in a range of pH levels but can degrade with prolonged light exposure. Great for anthotypes!
  

1. Flavonoids:

• Colors: Yellow, sometimes blue or red.

• Sources: Citrus fruits, onions, tea, apples.

• Characteristics: Contribute to plant color and UV protection, not highly sensitive to light or pH.
  

1. Tannins:

• Colors: Brown.

• Sources: Oak bark, tea, some berries.

• Characteristics: Provide color to plant tissues, quite sensitive to light.

Learn everything about Anthotypes inside the Alternative Processes Academy