Mini Scientists: Invisible Ink

Over the last few months, I’ve become aware of how much T enjoys doing experiments. I’m really keen to nurture this, but as subject knowledge goes, Science is probably one of my weaker areas. (As an aside, it is possible that I once thought petrol pumps were directly connected to oil sources and that central heating works by the boiler pumping gas to the radiators. No, I don’t know how I thought they got warm, either.) As well as Science, I’m hoping to try and do a range of STEM activities (Science, Technology, Engineering and Maths). Maths we already do a fair bit of, but I’d really like to come up with some more creative ideas for activities involving Technology and Engineering. I’m particularly keen to try and spark T’s interest and curiosity in these subjects while she’s still young, because as well as being great fun, I really want her to feel confident in these areas and so often society portrays these areas as being ‘for boys’. But we’re not here to discuss gender stereotyping, although feel free to check out my recent post on the subject.

Anyway, I’ve been having a bit of a think and coming up with some experiments we can do, and first up is invisible ink. If I had known that writing with invisible ink was quite so simple when I was reading the Famous Five, I would definitely have been doing this activity!

The activity is quick to set up and get started.

You will need:

* A lemon
* Some plain paper
* A few cotton buds

Simply squeeze the juice from the lemon and use the cotton buds to write or draw with the juice on the paper. You could try other implements, perhaps brushes, or cocktail sticks for finer writing. Leave it to dry, and then once dry, put it in the oven for around 10-15 mins to see your invisible writing appear!

T loved writing and drawing messages, and even made a secret message for Daddy to pop in the oven on his return home from work!

Taking it further

Since she’s enjoyed it so much, I decided it would be fun to extend the experiment. We decided to investigate which other liquids would make good ‘invisible ink’. I asked T which liquids she would like to include. She chose to compare: lemon juice, milk, water, orange juice, honey and white vinegar.

I started by dividing a sheet of paper into six to give her six spaces to write. She had a go at writing the name of each liquid – a good opportunity to practise her writing skills! I told her how to write honey, but she had a go at sounding out the rest herself. Once she had written each name, we left it to dry.

Once dry, we came back to see how well the inks were performing. Firstly: were they all invisible? T and I had a good discussion about the different inks, which were truly ‘invisible’ and which didn’t work so well. T noticed that the honey hadn’t really dried; it was still sticky and we could see it very clearly on the page. The orange juice was also more visible than the others – not nearly so clearly as the honey, but it was slightly yellow when dry. Observations made, we put them in the oven for the next stage: seeing whether the invisible writing became visible!

After around 15 minutes, the paper was ready! Four of the inks were visible, and two had remained invisible. T loved seeing which had worked and which hadn’t. We discussed which liquids made the best invisible ink by being firstly invisible when dry, and second, becoming visible on heating.

And now we know, there are so many fun ways to use it! Leaving secret messages for friends; as a start for a treasure hunt (perhaps for an upcoming egg hunt?); or a secret message from a story character would be a great way to inspire some creative thinking and storytelling. We’ll definitely be doing some more invisible ink activities in the future!

What she is learning:

There is so much to learn from an experiment like this!

  • Asking questions and being curious
  • Talking about observations
  • Observing and talking about similarities and differences
  • Thinking about why things happen

What are your favourite science experiments? Leave a comment below or let me know on social media! And for more inspiration for your mini scientists, check out our other experiments.

One Reply to “Mini Scientists: Invisible Ink”

  1. I used to love doing this. thanks for reminding me of it! I like the mentos in coke volcano

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