Invisible Ink Experiment


My daughter’s learning about Sir Walter Ralegh led her onto the subject of invisible ink this week. In times of court intrigue, secret messages were a vital way of getting information from one party to another. We visited the church of St Mary the Virgin, Beddington, next to Carew Manor, the home of Ralegh’s brother-in-law Nicholas Carew (who was previously a Throckmorton like Ralegh’s wife before he changed his name when he inherited the estate). It might be that Ralegh’s body (minus his head which was carried around by his widow Bess in a red case and was bequeathed to their son with whom the gruesome momento mori is thought to have been buried) is buried somewhere in the grounds of the church or manor but we will probably never know for sure. When we got home we decided to conduct an experiment to see which was the most effective invisible ink…


You will need: A selection of ‘inks’. We chose milk; lemon juice; apple juice; onion
(I crushed some onion in a garlic press to make a small amount of liquid); honey and water solution; sugar and water solution; beeswax (used like  crayon); and a solution of bicarbonate of soda and water. All but the latter two are ‘revealed’ through heat. For the bicarbonate of soda ink you can use a wash of grape juice to create a chemical reaction which will reveal your hidden message, although heat should work to reveal it as well. For the beeswax we used a wash of paint and water. You will also need small containers for the ink (like ramekins or even plastic lids from margarine tubs, etc.), paper to write on (we used parchment printing paper but ordinary paper is fine) and something with IMAG2416_1which to write such as a cotton bud, cocktail stick or similar. We used one of those plastic stylus you get with rainbow scratch art kits. Make sure you have some soapy water and kitchen roll to hand to ensure you wash the stylus thoroughly between each ink to avoid cross-contamination and to ensure a fair test. You will also need a hot oven for revealing the temperature-dependent messages and a brush for the other two. There are other options for the ink, including urine, but we decided not to try that one…

Method: Number each ink and label them on the paper. Dip the stylus in the ink and write a message on the paper next to the number and name of the ink. Leave it to dry and move on to the next ink, making sure you wash the stylus and do not smudge your message. Continue until you have tried out all the inks. You may want to use a separate sheet for the beeswax and bicarbonate of soda solution inks as you will be revealing this in a different way from the others.

Make a chart by dividing a sheet of A4 paper into two columns. List the number and names of your inks and head the columns: ‘Before’ and ‘After’. Look at your finished work and grade each ink out of five for initial effectiveness. Can you see the ink? Did it dry quickly and completely? Record the mark and any comments by the appropriate number.


Next you will need to reveal your messages. The honey and water solution had not dried and had to be blotted so we noted that another time we would need to use more water and dilute the honey better. We tried ironing the finished papers but we didn’t get any results at all so we placed them in a very hot oven (about 200 degrees Celsius) for not more than two minutes by which time the messages were visible. Using a brush, lightly paint the colour wash over the beeswax and then, using a different brush, brush grape juice over the bicarbonate of soda ink.

In the ‘After’ column on your chart grade the inks’ efficiency now that you can (or cannot?) read the messages. Are the messages clear and easy to read? Do they stay legible or do they fade?

Conclusion: Add the before and after grades together and declare an overall winner. To celebrate, write a full secret message with your winning ink!




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