How to Make Invisible Ink

Linda Casey                    Whistler Elementary School
                               11533 South Ada
                               Chicago IL 60643
                               (312) 535-5560

Objectives:

The students in grades four - six will learn how to make two types of invisible 
ink and write a message with each type of ink.  The students will write a paper 
comparing and contrasting each type of ink. 

Materials Needed:

    Ink # 1                       Ink # 2  
  Lemon Juice              Corn Starch
  Small glass              Hot Plate
  Toothpicks               Toothpicks or Cotton Swab
  Paper                    Pan                          
  Electric Iron            Iodine Solution
                            (1 teaspoon of iodine in 10 teaspoons of water)
                           Water
                           Paper
                           Small Sponge

Strategy:
                            Activity #1
The teacher will introduce the experiment by asking "What are some ways to 
write secret messages?".  After the discussion, the teacher will demonstrate how 
to make ink #1. 
                            PROCEDURE:
#1. Pour a little lemon juice in a glass.
#2. Soften the point of a toothpick in the juice.
#3. Write a message with the juice.
#4. Heat the message (with the iron) to make it visible.  The message should 
    appear brown.
                           
The students will be given materials to write messages and they will use the 
iron to make their messages visible.  The teacher will then pass out index cards
(each card will have the numbers 1, 2, 3, or 4 prewritten with ink #1 by 
teacher).  The students will make their numbers visible by using the iron to 
heat them and break up into groups according to their numbers. 

                            Activity #2
The groups will be assigned lab stations.  Each station will include materials
for making ink #2.  The hot plate will be set up at the teacher's station. 
                            
                            PROCEDURE:
#1. Mix a small amount of water with cornstarch (use about 2 tablespoons of
    cornstarch and 4 teaspoons of water) in the pan and stir until smooth.
#2. Heat the mixture for several minutes.  Stir.  (heat each mixture separately)
#3. Dip a toothpick into the cornstarch and water mixture and write with the 
    mixture on paper.  Let the paper dry.
#4. To observe the message, dip the small sponge into the iodine solution and
    carefully wipe the paper.  Do not get the paper too wet.  The message should
    appear purple.

Performance Assessment:

  The students will make the invisible ink #1 and #2 and write messages to
  each other.  They will also write an essay comparing and contrasting the two
  types of invisible ink.