This post is part of a series on chlorophyll, a molecule both plants and humans owe their lives to! This specific activity is a fun, easy, and art-inspired introduction to chlorophyll for children 2 years old and up where we will make paint from the chlorophyll in spinach leaves, then observe the fluorescence of the chlorophyll artwork with a black light! If you can paint, and not eat the paint, this activity is for you!
What is Chlorophyll?
Humans and other animals eat food, like plants, to get energy. But where do plants get their energy? The sun! Chlorophyll is a molecule in leaves that helps plants capture sunlight and use it as energy. It is also what makes plants green. Today, we’re going to take or “extract” chlorophyll from spinach leaves and use it as a paint!
What is Fluorescence?
After you paint with the chlorophyll solution, if you have a black light, you can see or “observe” a special ability of some molecules called “fluorescence.” When something fluoresces, it glows when a certain type of light shines on it. The molecule is taking energy from the light shining on it, then releasing it back as light of a different color. We normally see color because items reflect light of a certain color (green things reflect green light, but absorb the other colors). But, when something fluoresces, it is actually making or “emitting” light, so it looks like a glow to our eyes. When chlorophyll is in a leaf and exposed to sunlight, it captures some of the light and briefly stores it as energy in something called an “excited electron”. That electron can be passed to other larger molecules called proteins that eventually store it as chemical energy for the plant. If there is a back log in the chain of proteins, the energy in the electron in chlorophyll can be released as either heat or fluorescent light. (Try holding the black light over a leaf in the dark!) However, when the chlorophyll is outside the plant (and inside your paint!) away from the other proteins, it doesn’t have anywhere to put any of that energy from the light, so almost all that energy is released to make a brighter beautiful red fluorescence.
Caution: This activity uses rubbing alcohol (isopropanol). It is flammable. Do not consume it or get it your eyes (wear eye protection). Please keep it and the paint away from open flames, in a well ventillated room, and do not do this activity with children who still put items into their mouth. It is fine for kids to get rubbing alcohol on their skin (it is usually used as a disinfectant for cuts and scrapes), but the paint will dye hands and clothes green. The paint is basically a grass stain in a bottle! Wear clothes you wouldn’t mind turning green, same for your workspace. Wear eye protection for splashes. Do not look directly at black lights, especially the LED ones. If you don’t want to use isopropanol, vegetable oil may also work, just not as well, and you may have to blend the leaves and oil to a pulp, then strain. Have fun, and be safe!
Make Fluorescent Chlorophyll Paint from Spinach Leaves
- Rubbing Alcohol (Isopropanol 91 vol%) (the typical one available at drug stores)
- Spinach (any type is fine, but we recommend frozen)
- Bowls (cereal sized, non-porous)
- Strainer or large funnel
- Cheese cloth or paper towels
- Paint brush
- Washable surface, optional (like a large baking sheet)
- White paper (for normal painting)
- Black paper (to view the fluorescence)
- A black light (available on Amazon through the following links)
1. Thaw a cup of frozen spinach in the microwave or stove top till steaming. (If using fresh spinach, cut or chop it roughly, then heat)
2. Add ¼ cup of rubbing alcohol (isopropanol) to the hot spinach.
3. Mix it around a bit, then let it sit for 5 minutes, covered.
4. Push the spinach to the side with a spoon to look at the liquid, it should be a nice dark green. Give it a couple good stirs and mushes.
5. Put your cheese cloth or paper towel over the strainer or funnel and strain the liquid from the spinach.
6. If you have a cheese cloth, squeeze the leftover liquid from the spinach. (This is the good stuff, but if you only have paper towels, don’t worry. The paint won’t be as dark, but it will still work.)
7. If you want more paint, add a little more isopropanol to the spinach and repeat. (No need to get more spinach, there is still tons of chlorophyll left in the used batch.)
8. If your paint isn’t as dark as you would like it, let some of the isopropanol evaporate, but don’t put it in the sun, it will turn brown. You now have a solution enriched with chlorophyll. There are still proteins and other small molecules from the plant in the paint, so it is not pure, but it definitely is the bright beautiful chlorophyll green!
9. Hand out white and black paper on baking sheets or trays, if desired. The isopropanol may cause some of the black dye in your paper to leak through to your painting surface, so I recommend putting something non-porous and washable under your artwork. Then, paint away!
10. To see fluorescence with the black light, you should paint on dark paper. To see the stunning pigment you created, paint on white paper!
11. While the paint on dark paper is still wet, go into a dark room, turn on the black light, and illuminate the artwork. The red glow is absolutely beautiful and fluorescence is something many kids have never seen before.
12. Put your paint in an air tight container and it will keep for a few more days. It may need some mixing, but it should still work fine!
Note: Do not leave your paint or paintings in the sun, they will “photobleach” and turn brown.
Note: You’ll need to paint on black paper to really see this effect brightly. If you use white paper, the background is so bright under the UV light that the glow from the fluorescence will be mostly masked. However, if you don’t have dark paper, if you pool the paint on white paper, and shine the black light on it, you may be able to see some fluorescence. You can also just shine the light on the pot of paint or smear it on a baking sheet (in a dark room for the best glowing effect).
Note: If you’re doing this with a large group, some paintings may dry before the kids get to see their paintings with the black light. It may be better to set that part of the activity up separately than the painting segment. For example, all the children can paint with the chlorophyll on white paper to take home, then when they are finished, you quickly paint a design on black paper and usher them into the dark room to see the fluorescence. Also consider going in groups.
Note: If the paint is drying too fast for you to play around with the fluorescence as much as you want, keep an eye on our blog for an oil based fluorescent chlorophyll paint soon! It doesn’t dry as quickly, and you can make beautiful dripping designs on the paper.