More fluorescent, glowing science fun! This time we made glowing ice cubes, using just one easy-to-find ingredient.
Can you guess what it is? Hint: It’s the same ingredient that we used to make our water beads glow earlier.
Need another clue? You should be able to find it in the drinks aisle of your local grocery store. It has a bitter flavour.
Still unsure? OK, I’ll let you off the hook.
The secret ingredient is: Tonic Water.
More specifically, you need tonic water that contains a small amount of quinine listed as one of the ingredients. (Most brands do, but just double check). It doesn’t matter if it’s regular or diet tonic water, we’ve tried both and they work equally well, as it’s the quinine, rather than the sugar, that makes it glow. (Although as a side note, we do prefer playing with diet tonic water ice as it’s less sticky…)
You’ll also need a dark room (or dark box) and a black / ultraviolet (UV) light (long wave UV-A ultraviolet light with either LED or blb bulb). You can find them easily online – they are often marketed as dog or cat stain finders. We’ve tried this one and we currently have two of these torches.
What happens is, the quinine in the tonic water ice absorbs the ultraviolet light, which is invisible to the human eye, and then emits it back at a visible wavelength. Or, in other words, invisible light goes into the tonic water ice, and comes back out as visible light. Cool!
And it really, truly does glow!
Have a look below at the difference between the regular water ice and tonic water ice. I took these photos in one of my kids’ black canvas toy boxes, which I’d turned on it’s side, as an easy way to create a very dark backdrop. The first image is with natural light hitting the ice cubes from our laundry window. You can just make out that the tonic water ice (in the middle) is slightly whiter and less transparent than the regular ice (on the sides), but essentially they all look similar. (The ice cube moulds were slightly different shapes, but otherwise….)
Now have a look at what happens when I close the laundry window and turn on the black light torches.
The UV light is hitting all the ice cubes roughly equally here, but you can really see that the tonic water ice cubes have a strong blue glow (they look like they are emitting blue light from within), whereas the regular ice cubes just reflect a slight violet tinge.
Regular ice cubes just by themselves are a fantastic open-ended sensory play material that kids love. It’s cold, it’s wet, it’s slippery! You can stack them – can you build a tower? Add water, and it floats! When it melts, it turns from a solid into a liquid. You can eat it – what does it taste like?
Add tonic water ice cubes into the mix, and it opens up even more play possibilities. Can you see a difference between the two types of ice cubes? Can you feel a difference? Can you taste a difference? What does tonic water ice taste like? Do you like it? What do you think makes it glow?
The kids wanted to break the ice cubes apart, so I let them have a go with their (real, but small) hammer. My kids play with real tools quite a bit, but I’ll let you judge whether this would be appropriate in your house.
(As one of my lovely readers Debbie pointed out, you might want to put on safety googles on your kids first, in case the ice shatters and little pieces fly up into their eyes. Good point, I should have thought of that. We have these ones, which my kids usually love to wear.)
And then they tasted. They decided that the water ice cubes were delicious! The tonic ones they weren’t such a fan of, although they did go back for third, fourth and fifth tastes, just to make sure.
For more glowing fun, check out the glowing water beads and glowing slime that we made earlier. (You can find all our glowing ideas on our Glowing Science page).