Invisible ink – 1


1. One tablespoon of cornstarch
2. A cup of water
3. A paintbrush
4. Paper
5. A piece of cotton
6. One tablespoon of iodine tincture mixed in a cup of water (Warning: Direct contact with this chemical can be harmful)


1. Mix the cornstarch in a cup of water very well.
2. Dip the paintbrush in the cornstarch mixer. Now use the paintbrush to write something on the paper. (Usually it’s a secret message because the writing is invisible! :p)
3. Let the secret message/invisible ink dry on the paper.
4. Now dip the piece of cotton in the iodine tincture solution and then rub the paper with that cotton.
5. Now observe what happens.


The invisible or secret message you wrote on the piece of paper should not be so secret anymore! It should appear on the paper in dark purple letters.


Normally iodine has dark red color. But when iodine comes in contact with starch, its color changes to a dark purple color. Different kinds of foods such as rice, potatoes etc. contains a great amount of starch. You can find out that whether a food have starch or not by adding only a drop of iodine to them. In our experiment we used cornstarch solution to write invisible or secret messages. By using cornstarch on the paper we provided the paper a source of starch which can be tested by iodine. The area of the paper which contains starch becomes dark purple after adding iodine tincture on them. This is how you would be able to create and read your invisible or secret messages. And you can do all of this just by using a simple chemistry!


1. Blend a little bit rice in the water and use it instead of cornstarch solution to see what happens.
2. Blend a really small piece of potato and use it instead of cornstarch solution to see what happens.
3. Try some other foods instead of cornstarch to see what happens. To do this you can first be sure if that food has starch or not by adding a drop of iodine on it.


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