Experimenting with Invisible Ink

The kids and I tested 3 kinds of invisible ink today. Two of them were abysmal failures and one worked pretty well. In any case it was fun. Which of the above three ingredients do you think was the winner?

1. LEMON JUICE

Squeeze the juice from a couple lemons into a small bowl. Apply with a toothpick or small paintbrush. Let dry. Use heat to reveal message.

Note to self: use real lemons next time! That might work, but the lemon juice didn't really. It stained the paper right away, and didn't really change colour with heat applied. I'm not too sure how detailed a picture was on these two pages anyways. The lemon juice is very watery so I think it was hard for them to control where it went on the page, even with a small paintbrush.

2.  CORNSTARCH

Cook 2 TBSP cornstarch and 4 TBSP water in a small pot until it makes a gravy. Do not overcook. Let dry. Apply with a toothpick or small paintbrush. Let dry. Use a mixture of 1 part iodine to 10 parts water to reveal message.

It took more water than that before it could be mixed for me and it still wasn't 'gravy', and the results weren't stellar. Our iodine mixture may have been to blame but since it didn't work at all, I can't say what the problem was. The colour on the pages is just them painting on the iodine after.

Are you ready for the one that DID work now?

TA DA! This one you should try!

3. BAKING SODA

Mix equal parts baking soda and water. Stir vigorously, and apply with a toothpick or small paintbrush. Let dry. Use heat to reveal message.

The baking soda ink was also the most invisible once applied.

Here's an article on how invisible ink works.