Method:

You will need 2 teabags and 6 iron tablets (the kind you get from health food shops - a form of Iron Sulphide) Brew the tea for 1/2 hour in 250 mL of boiling water. While you wait for the tea to brew, dissolve the 6 iron tablets in 2 teaspoons of hot water. After the tea has brewed, pour in the iron solution (leave the undissolved bits behind); note the fizzing. A chemical reaction has occurred!. Leave overnight.

You have just formed Iron Tannate from the tannic acid in tea!

Use a paint brush to paint a message on a peice of paper. If you have an old nib pen, try out your ink to see how well it works. Your ink may damage the metal as nib as it is likely to be acidic.

Iron tannate ink was called ‘iron gall’ ink, used in Europe from about the 11th Century onward.

Today, modern pens use alternative inks as the acid in our iron tannate ink damages the paper it is on.

1. Secret Agents might like to try our Invisible Ink...
2. Test this ink and compare it to the ink you can buy from the shops.
3. Find out more about how people first kept records (stone tablets, papyrus, cloth, etc)
4. Did they use the same languages, or symbols (what are runes, hieroglyphics, etc)?
5. The interactive pages...identify these pieces of lab equipment
6. The interactive pages...weird metals and gases hide in this Periodic Table