SET: Invisible Ink

Today for our Science Experiment Thursday, we made some invisible ink:

All you will need is:
-Lemon Juice
-A piece of paper
-Paintbrushes
-A heat source (stove, strong light bulb, candle, etc.)

I had Monkey J squeeze some lemon juice into a bowl and then use a paintbrush to make a drawing:

Monkey A also got involved in the process:

Meanwhile, I made a Mickey silhouette:

I let Monkey J do some painting while we waited for the lemon juice to dry on the paper:

Once it was completely invisible:

We moved the paper over to an open flame on the stove.  Luckily for me, my dad was visiting so he was able to help:

Right away the flame picks up the lemon juice:

Hold it over the heat a bit longer and your invisible ink suddenly becomes visible!

Pretty neat!  So how does it work?
Lemon juice is mildly acidic, which weakens the paper.  When the paper is heated, the juice browns first because it has been weakened by the acid.  You can also use vinegar and other fruit juices.

A super fun experiment!