It’s a classic science reaction that dates back to the late 1800’s. The Classic Iodine Clock Reaction reaction was used by magicians and psychics at Halloween time to remove the evil thoughts or evil spirits from someone’s body and mind. They obviously doesn’t actually remove anything…they just make starch.
This reaction is delayed for a few seconds, which can make the subject startle and believe that they actually made the liquid change. For more information on the Landolt Clock Reaction, visit the Think Ink Experiment.
Note: This method is not recommended for anyone other than a chemistry teacher or a chemical demonstrator. Safety goggles must be worn at all times and gloves are required when handling sulfuric acid. Preparation for this demo must be conducted in a well-ventilated area. The Steve Spangler Science team developed a safer do-at-home version of this experiment called Think Ink. This kit is a preferred version to use in a Haunted House or Halloween party with adult supervision.
How does it work?
This reaction is referred to as the Landolt Clock Reaction. There are three steps in the process that cause this amazing reaction. When you prepare the Solutions A, B, and C, the chemicals begin to mix and form new chemical compounds. This is a very slow reaction, so you don’t see any outward changes. When you begin to pour the solutions together a much faster reaction occurs, which leads to the third reaction which is instant. Suddenly, and immeasurably quickly, the clear liquids turn into a jet black iodine-starch complex. These reactions happen at different intervals because different chemicals react at different speeds.