The BIOTOPIA Lab black light spectacle
Be careful when handling the chemicals (methylated spirits, acetone, acetic acid) and the UV light. Always point the lamp away from yourself and other people! The UV light can cause damage to your eyes. It is best to carry out the experiments together with an adult person and keep away from open fire.
Suitable for all ages
Children should perform the experiments under adult supervision
Especially interesting for:
Color lovers, the curious and those who love surprises
Duration: approx. 30 minutes to 1 hour
For this experiment you need:
A UV lamp
A mortar or a grating bowl with pestle
A few green leaves (preferably fresh spinach)
Clean, fine sand (e.g. quartz sand for aquariums)
Methylated spirits (don't worry: we won't set it on fire)
A small glass (e.g. shot glass)
In this experiment, we will make the chlorophyll in the leaves glow. It is used by plants for photosynthesis.
Plants (and certain bacteria) use light, water and carbon dioxide to put together something new: namely glucose and oxygen. In other words, energy-rich organic substances are created from energy-poor inorganic substances with the help of solar energy. This is called photosynthesis.
In principle, yes. All fresh leaves that contain sufficient chlorophyll are theoretically suitable for this experiment. We used spinach because it is soft and therefore it is easy to get the chlorophyll out of the cells.
Plants have specific organelles in their cells for photosynthesis. These are called chloroplasts. The chlorophyll is stored in them. To dissolve the leaf green, we must therefore destroy both the plant cells and the chloroplasts they contain.
For this experiment you need:
A UV lamp
A tall glass as large as possible
A young chestnut branch with smooth bark
(a small branch is sufficient)
A knife (does not have to be very sharp)
A dark background (e.g. black cardboard)
Dirt catching cloths (from the drugstore)
The substance that glows so blue here is called aesculin - a compound related to the woodruff aroma coumarin. Aesculin is named after the horse chestnut (Aesculus hippocastanum), in whose bark it was first detected.
Yes, it works! The first person to find this out was the German chemist Paul Krais. If you get dirt-trapping cloths at the drugstore, you can try it out for yourself: Dip a cloth in your chestnut water and then compare it to an untreated one under black light. Even today, this effect is used to lighten clothing.
Unfortunately, this experiment does not work with every bark. But there are a few more trees that have bark that can be made to glow in other colors: Barberry, for example, glows yellow and ash green!
For this experiment you need:
A UV lamp
A brown egg (the browner the better)
An egg cup
Spirit or nail polish remover
A pipette or a teaspoon
A saucer, or other surface
Brown protoporphyrin IX plays an important role in living organisms as a precursor for other compounds such as heme (b) and chlorophyll.
From protoporphyrin, humans and animals can produce heme, the coloring component of our red blood pigment (hemoglobin). We can use it to bind and transport oxygen. At the center of heme is an iron atom. In the chlorophyll of plants, on the other hand, magnesium is at the center.
You cannot tell from the plumage of chickens whether they lay white or brown eggs. A good indication, however, are their ears! Or rather: the so-called ear discs. These are skin flaps under the ear, which lie directly behind the eyes. Hens with white ear discs lay white eggs. Hens with red ear discs brown.
What exactly happens in your glass and where can you find a similar glow in nature and in everyday life? And what does all this have to do with platypuses? Has your curiosity been awakened?
Then you've come to the right place! Here we show you clearly what fluorescence is, how it works and how it differs from other luminous effects. There are also some interesting facts about fluorescent animals and tips on what else you can investigate with your UV lamp.
The luminous phenomenon that you can observe is called "fluorescence".
To understand it, you have to look at the level of molecules (particles that make up a substance) and the properties of light.
A light source, e.g. the sun, emits light. The light of the sun appears white to us. But actually it is composed of different colors. You can see this in a rainbow, for example. The colors we see in the rainbow are only a small part of the light spectrum. In addition to the parts of the light visible to humans, the sun also emits ultraviolet light (UV light) and infrared light. These two types of light are not visible to the human eye.
UV light is relevant for our experiment. Have you ever had a sunburn? UV light was responsible for that. It is very energetic. So energetic that it can cause damage to your skin.
A fluorescent molecule has a system called a fluorophore. This system usually consists of certain chemical groups. If the molecule has a fluorophore, it can be excited by UV light. Here you can see what happens:
Energy-rich photons of UV light strike the pigment particles.
More precisely, they strike electrons in the atomic shell of the pigment particles.
Here we look at the processes using the example of an electron and its energetic states.
The incoming photon transfers energy to an electron of a pigment molecule. This means that the electron is moved a bit away from the atomic nucleus. This excites it to a higher energy level. This excited state is energetically unstable.
First, some of the absorbed energy is released in the form of oscillations.
The electron is then in a lower-energy excited state.
At the end, the electron returns to its ground state. In the process, a lot of energy - in the form of light - is released. This is also the step that we perceive as glowing.
The emitted light is now no longer as energetic as the incident UV light.
As a result, it is visible to humans and appears to us as a colored glow.
If you don't know the answer to this question, it's not surprising.
The fact that platypuses fluoresce when exposed to black light
was discovered only recently. But they are not the only animals that possess this property. Have a look for yourself by moving your mouse cursor over the pictures!
Platypuses are strange animals. And not just because they fluoresce under black light: Did you know that female platypuses lay eggs but suckle their young? Platypuses are one of the few egg-laying mammals in the world. Their duck-like beak is also rather unusual for a mammal. And as if all this were not unusual enough, male platypuses also have venomous spurs on their hind legs.
Who knows what else we will find out about these fascinating animals in the future?
© J. Martin, Northland College; from Anich et al. 2020, Mammalia.
Not everything that glows equals fluorescence. If you irradiate a scorpion with UV light, for example, it starts to glow. If you take the light source away, the glow stops at the same moment. The fact that the glow stops as soon as the light source is switched off indicates that it is fluorescence.
However, there are also substances that continue to glow after the light is switched off - sometimes even for several hours. This phenomenon is called phosphorescence. Some minerals possess this property. If, for example, the hands of your watch or the luminous stars on your ceiling glow in the dark, this is also phosphorescence.
A firefly glows even in the dark, it doesn't need an external light source to do so. What's behind it? A chemical reaction takes place in fireflies, releasing energy.
And we can then perceive this energy in the form of light. The phenomenon is called bioluminescence.
It has long been known that chameleons are true masters of color change: For camouflage or to impress competitors or females, they can change their color several times within a few minutes. They owe this to special cells in their skin (so-called chromatophores).
© Fotos: David Prötzel.
But did you know that chameleons also glow under black light? However, the origin of the fluorescence is not in the color cells of the skin, but in the bones of the chameleons:
The fluorescent patterns result from the bony tubercles of the skull and other skeletal elements. Where the skin is particularly thin, the fluorescence of the bones can be seen shining through (Prötzel et. al. 2018).
We have compiled a small list of other things that glow under UV light.
Go exploring with your black light lamp and discover everything that lights up in its glow!
The fact that flying squirrels also glow colorfully in the light of a black light lamp has also only recently been discovered.
The researchers were certainly amazed when they found this effect for the first time!
Why some animals and plants fluoresce is often unexplained.
However, it is known that some animals - unlike us - can see UV light. These include bees, for example.
© Fotos: J. Martin, Northland College; from Anich et al. 2020, Mammalia.
The world of fluorescence is diverse and large. Unfortunately, we cannot show you everything about it.
If you want to do more research on these topics, we recommend the following links for your investigations.
You can't get the fluorescent platypus and flying squirrel thing out of your head? Here you can learn more about the discovery of this extraordinary property.
© The New York Times
You want to know what the underwater world looks like in black light? Then watch this video of a night dive and dive into an unknown world.
© Elisabeth Lauwerys
The children's radio of the Bayerischer Rundfunk visited us in the BIOTOPIA Lab and tried out some of our Lab @ Home experiments, including one of our fluorescence experiments. [In German]
© Mischa Drautz, Bayern 2
On this page you will find more exciting experiments and information from the world of fluorescence, phosphorescence and bioluminescence. Here we also got inspired for our eggshell volcano. [In German]
© Universität Jena
Fluorescence and phosphorescence are hard to imagine - even for big kids and adults. If the explanations of the diagrams are too complicated for you, take a look at this comic. Afterwards, you will surely have a good grasp! [In German]
© SimplyScience Stiftung
You don't have a UV flashlight right now? Then try this animation. Fluorescence is explained using the example of the mineral calcite - you yourself determine whether the light is on or off. [In German]
© Thomas Seilnacht
Created by our Lab Pilots and coworkers Luisa, Amelie, Dominic, Thassilo, Timon and Kathrin.
Special thanks to David Prötzel and Jonathan Martin for sharing their fascinating wildlife images.