Do you remember adding food dye to a vase of flowers to see how the colour is soaked up? I don’t remember how old I was when I learned you could do this, but it’s always been fun to do, no matter how old I am! My eleven-year-old loved it, but she would have enjoyed it thoroughly when she was very little, too. This particular version is a fun twist on an old idea, and is quick and easy to set up – though could be a little messy, which is why we started outside.
What You’ll Need:
• Fresh cut flowers – if using bought flowers, remember to cut fresh ends on the stems, preferably with a sharp knife
• Food dye
• A highlighter
• Water
• Small glass jar
• UV torch – remember that this is concentrated UV light and should never be pointed at your skin.
• Pliers, tin snips, or craft knife
Step 1
Harvest a few flowers from your garden, or buy a couple at the florist, and strip them of leaves. We picked a couple of roses from two of our rose bushes just as the flowers were starting to open – we have so many blooms this year! Though I am currently at war with the aphids!
Step 2
Add the food dye to your small glass jar.
Step 3
Using your pliers, tin snips (I just pinched the highlighter slightly with my tin snips and it popped right open!), or craft knife, get into your highlighter and add the ink wick (that squishy, fibrous bit inside a marker or highlighter where all the ink is held) to your jar of food dye, along with a small amount of water.
Step 4
Add your flowers! It’s best to re-cut the very ends of your flowers for them to best take up the dyes.
Step 5
Wait! Now, you have a couple of options about how you complete this activity. We allowed our flowers to sit in the dye for two days (they were quite firm buds and didn’t want to open up so we gave them more time, but really, they were picked a little early and wouldn’t fully open). They absorbed an enormous amount of pigment, and were entirely blue by the time we took photos. Under the UV light, they looked incredible!
But I realise that I have a patient eleven-year-old, so in case you have a little one who doesn’t want to wait to see what happens with this activity, I went back to my rose bushes and picked two open flowers, took photos of them, then put them in the dye for just two hours, and took photos again. As you can see, it’s still a pretty amazing effect!
What’s happening?
Like people have veins and blood vessels, plants have xylem and phloem which draw up water and nutrients from the ground, as well as doing some other stuff, but we’ll keep things simple for this activity. Here, our flowers are sucking up the pigment (the colour particles in the food dye and highlighter ink) in the water, which stays in the xylem of the flowers. The reason the colour gets deeper over time is because the flower draws up water, dye and ink, then the water evaporates, leaving behind the pigment, and then draws up more water, dye, and ink. Repeat this over and over and you have deeply coloured flowers that fluoresce strongly under a UV light. But why? Well, many highlighters contain ink that is fluorescent, which is a scientific term for when a material absorbs light of one colour, but then emits light of a different colour with a longer wavelength. The reason this fluorescence is so striking, is because the highlighter ink is absorbing ultraviolet light that human eyes can’t see from our UV torch, and then emitting it back as a light we can see, which makes it look like the flowers are glowing under the UV light! How cool is that?!
