In this challenge we talk about the colors that we can see in nature, the biological pigments. Biological pigments are substances produced by colored organisms. The reason these molecules have colors is the result of different chemical processes. But do you know about biological pigments? The color of an animal’s skin and hair, for example, depends on the pigment called melanin; and on the green and purple color of the parts of the upper figure, the chlorophyll and anthocyanin pigments.
But biological pigments have no decorative function, they perform physiologically important functions for organisms; melanin, for example, absorbs ultraviolet radiation when our skin is exposed to the sun’s rays, defending the skin against solar attack. Chlorophyll is the most important pigment found in plants and is a compound that plays a fundamental role in photosynthesis.
Are you clear now what biological pigments are? Let’s play with pigments!

In the following lines you are presented with two challenges: One “Pigment Dyeing” and the other ” Pigment Chemistry”. You need different things each time:
To dye with pigments:

  • Vegetables and foods of different colors:
  • Carrots.
  • Beets.
  • Spinach.
  • Coffee beans.
  • Spices: turmeric, chaste
  • Water.
  • Vinegar.
  • A cooking container and containers to put the eggs in dye.
  • White eggs.
  • Paper (better if it is to paint watercolors).
  • Brushes.

Chemical analysis of pigments:

  • Purple cabbage.
  • Water.
  • Sodium bicarbonate.
  • Bleach.
  • Vinegar.
  • Lemon juice.
  • Cooking container.
  • Knife.
  • Plastic cups.

Dyeing with pigments:
Put the vegetables and the egg in the oven: Put the vegetables/food you are going to use for dyeing in a container (before grinding the vegetables/food). When the water is boiling, put an egg in the same container and cook for 10-15 minutes with the vegetables/food. Repeat the process with different vegetables/foods to obtain different coloured eggs.

  1. Put the eggs in coloured water: Once the eggs are cooked, take them out of the water, put them in a container and fill the container with the cooking water used.
  2. Add vinegar: Add a spoonful of vinegar to a bowl covered with egg-coloured water and leave it to stand for at least 8 hours.
  3. Take the eggs out of the water and let them dry: Once the dyeing time is over, take the egg out of the container and let it dry.
  4. Painting with coloured water: You can paint on porous paper that is used to paint with watercolours with the coloured water that is leftover after cooking the vegetables.
  • To get different colours you can use the following foods: blue (blueberry), yellow (Turmeric), orange (paprika, carrot), brown (coffee), pink (beet or cranberry), green (spinach) and purple (pink wine).
  • If you add more vinegar you will get more intense colours.

Pigment chemistry:

  1. Purple cabbage infusion: Chop the purple cabbage with a knife and cook it with water for 15 minutes. Leave to cool and reserve water (purple).

Divide the water from the purple cabbage into glasses: When the water you have used to cook the cabbage has cooled down, distribute it in glasses, placing approximately the same amount in all of them. You have to fill five glasses.

  1. Add other ingredients to each glass: In the glasses with purple cabbage water add the other ingredients and observe what happens:
  • Glass 1: Lye.
    – Glass 2 : Baking soda.
    – Glass 3 : Water.
    – Glass 4 : Vinegar.
    – Glass 5 : Lemon juice.

What happened?
In the cooking of the cabbage, pigments called anthocyanins are extracted, colouring the water purple. Anthocyanins give the leaves, flowers and fruits of some plants a red, blue or purple colour, and changes in their structure as a result of the change in pH cause a change in colour.
This is why the colour has changed when the purple water present in the glasses is mixed with other compounds. Vinegar and lemon juice are acidic and reduce the pH of the purple cabbage water. However, sodium bicarbonate and lye increase the pH of the water. These changes in pH cause the purple water in the containers to change colour. Pouring water into purple water does not change the colour because the pH of the water is neutral. In this case, the purple colour will lighten, but not change colour.

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1 Response

  1. Antoine says:

    For obvious reasons your content on this page is spot on for multiple reasons. It stays away from the common mistakes and traps most fall into: using bad alternatives. Keep it up!

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