Home Education Science Experiments Invisible Ink and Flammable Iron

Invisible Ink and Flammable Iron

Invisible Ink and Flammable Iron

The theme for tonight’s chemistry project was iron. When you think of iron, you think of a metal used to build strong and durable objects like hammers, cars and sky scrapers. But this science project uses iron to make invisible ink and later we’re going to burn it.

The first project was pretty simple. Najwa fills a marker with tannin and writes a message. It has no color so you can’t see what she’s writing. It’s invisible ink.

Tannins are a compound class of plant origin. They can be found in tea leaves, nuts, oak, and other tree bark. Tannins boast a brown-yellow color, astringent taste, and discreet, pleasant aroma (you may carefully smell the solution). The main ingredient of the tannin solution in our kit is tannic acid, which is one of the most easily-available tannins.
Najwa filling up the marker with tannin to write her secret message.

Next you apply the iron(II) sulfate to the invisible ink. The tannin reacts with the iron ions and form an intense-colored compound. This reveals whatever is written in the invisible ink so that it becomes readable.

That was easy. Anticlimactic but we still had iron to burn. The project was to take steel mesh, connect it a power source and let the electricity course through the thin strands of iron until it caught fire.

When we first connected the power, it didn’t seem to be doing anything. It took a while before the iron heated up. Najwa at one point touches it and feels the heat. You could then see the steel mesh browning before it spontaneously bursts into small flames.


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