Invisible Ink

Useful information
Kit List: 

Paint Brushes
Light bulb or other source of heat
Lemon Juice
Bicarbonate of soda
Fruit Juice

Frequency of use: 

Use two methods of invisible ink.

Lemon juice method.
Use a paint brush to write on the paper in lemon juice, allow this to dry, then hold it up to the light (heat source). It should brown in the places where the writing was.

How does it work?
The lemon juice is acidic. This means that it attacks the paper, so the parts it is on are thinner and burn more quickly.

Backing soda method
1. Mix the water (1/4 cup) and baking soda (3 tablespoons) in a cup with a teaspoon.
2. Get them to dip a paintbrush in the solution and write a secret message, thinly. Then wait for it to dry.
3. Brush some blackcurrant/grape juice across the sheet and the message should appear.

How does it work?
Baking soda is alkaline. Blackcurrant/grape juice is acidic. When you put these juice concentrates on top of baking soda, a chemical reaction takes place which produces a colour change in the paper.

Other things to talk about: cryptography.

Risk Assessment
Date risk assesment last checked: 
Sat, 23/01/2016
Risk assesment checked by: 
Fiona Coventry
Date risk assesment double checked: 
Fri, 13/02/2015
Risk assesment double-checked by: 
Risk Assessment: 
DESCRIPTION Compare two types of writing in invisible ink. 1) Lemon juice on paper, acid “attacks” paper, so if heated the “attacked" parts go brown first. 2) Use baking soda in water to write with, then cover page in blackcurrant or grape juice and the message should be revealed.
RISKS 1) Slip hazard if anything is spilt.
2) Any of the juices are irritant to eyes and cuts.
3) Light bulb gets hot.
ACTION TO BE TAKEN TO MINIMISE RISKS 1) Use small amounts of liquid in a large container, keep liquids in secure location away from electrical equipment.
2) Use paintbrush for writing on paper, don’t squirt any of the liquids.
3) Ensure no one touches the bulb.
ACTION TO BE TAKEN IN THE EVENT OF AN ACCIDENT 1) Clear up any spillage straight away. Call first aider in case of injury.
2) Call first aider in event of incident. Use eyewash to wash out of eyes if trained and confident to do so.
3) In case of burn, call first aider, encourage them to run burnt area under cold tap.