You will need
- birthday candle
- plasticine or clothes peg
- paper
- lemon juice
- small paint brush
What to do
Children should be supervised by an adult when doing this activity.
People have been reading by candlelight for ages, but this activity is a bit different.
Squeeze some lemon juice in a cup. Dip the paint brush in the lemon juice. Write an “invisible” word or draw an “invisible” picture onto paper. Allow the paper to dry for an hour or more.
Use plasticine or a clothes peg to hold a candle upright on a safe surface. A safe surface can be made using a large piece of aluminium foil or a large cooking tray.
Light the candle.
Move the paper back and forth over the flame until you see the writing or the picture.
Caution: Keep moving the paper above the flame, or it may catch on fire!
Think about it
Heat from the candle flame helps lemon juice to react more quickly with oxygen in the air. A brown coloured substance forms, making it possible to see the word or picture.
Explore more
Try using milk instead of lemon juice to write an invisible message. Once dry, can you use the candle flame to read the message?Try other liquids. Which ones reveal a message when heated by a candle flame?