Making the visible invisible again!


1. A Secret or invisible message written by using water and cornstarch mixer (See this blog: Invisible ink – 1) after making it visible by using tincture iodine.
2. A clean paintbrush
3. ¼ cup of saliva (Can be obtained by just only spitting into a cup!!!!! :D :P)


1. At first dip the paintbrush into the saliva and then paint over the visible letters in the secret message which is written by cornstarch mixer.
2. Observe if there is any change in the message.
3. If you don’t see any change in the secret message, then repeat the same process. This time perhaps use another person’s saliva.


1. Over time the dark purple letters which was visible after using the tincture iodine might fade and become invisible again.
2. Your saliva might not just make it invisible again coz some peoples saliva do not actually work on those dark purple letters written by cornstarch mixer.


In the human body many different kinds of foods are broken down. Different kinds of proteins are responsible for the breaking of these foods. Many of these foods are actually found in the saliva. The protein which is responsible for breaking down proteins is called amylase. This protein named amylase is found in the saliva as well as the intestines and stomach. Amylase is an enzyme. So it can be used over and over again to convert or transform starch into a substance or molecule which the body can easily use. This enzyme breaks down starch into sugars. Sugar is a much are simpler molecule than starch so the body can easily use it. When saliva is added to the secret or invisible message any amylase in the saliva will transform the starch used on the paper to write the invisible message into sugar. When starch on the secret message is transformed completely into sugar the dark purple color of the letters written in the message disappears and the secret message i.e. the invisible message becomes invisible again.
Now to answer the question - why saliva of some people doesn’t work on starch? The answer is simple! Saliva of some people doesn’t actually contain amylase. So that’s why saliva of those people is unable to transform or convert starch of the visible secret message into sugar. The dark purple color of the letters of the secret message will not be affected and so they won’t become invisible again. The presence of amylase in ones saliva is actually genetically determined. So the chances are really great that his/her parent’s saliva also do not contain amylase. So if your saliva do not work in this experiment try using one of your friends or neighbors saliva. in short you should get saliva from an unrelated person if your saliva do no work on the secret or invisible message written with starch.


Try using the saliva of different house pets such as cats or dogs to see what happens. But be really very cautious about it and be really very careful.


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