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Steve Spangler Science - Think Ink Chemistry Demonstration

About.com Rating 4.5 Star Rating


The iodine clock reaction is a color-change chemistry reaction.

The iodine clock reaction is a color-change chemistry reaction used to demonstrate oxidation and reduction chemistry.

Anne Helmenstine

The Bottom Line

The Steve Spangler Science "Think Ink!" kit is a chemistry demonstration in which you mix together two clear liquids to cause a color change to blue and black. The reaction can be recharged again and again to produce the color change. The demonstration illustrates oxidation and reduction reactions and rate of reaction as a function of temperature and concentration. It's a great project for raising interest in chemistry.


  • Reliable, dramatic color-change reaction.
  • Easy to recharge the reaction to see it over and over again.
  • Enough materials to perform the demonstration 30 times.
  • The demonstration only takes about a minute to set up.
  • Several chemistry concepts can be taught based on the demonstration.


  • Reactants are labeled as 'kitchen chemicals', not by their actual names.


  • This kit contains everything you need (except water) to perform a color change chemistry demonstration.
  • Two clear liquids are mixed. The mixture turns blue and then black. Addition of another chemical restarts the reaction.
  • An instruction sheet explains how to perform the demonstration and describes the chemistry behind the color-change reaction.

Guide Review - Steve Spangler Science - Think Ink Chemistry Demonstration

This is a good-sized kit that includes everything you need to perform a color change chemistry demonstration that you can use to illustrate principles including oxidation and reduction reactions and reaction kinetics. The kit includes safety glasses, two jumbo plastic test tubes, a test tube stand, 30 starch pellets, three containers of chemicals to initiate the reaction and recharge it, measuring scoops, stirring sticks, and detailed instructions.

I found the instructions for the Steve Spangler Science "Think Ink!" demonstration easy to follow and understand. The color change is caused by a reaction between iodine and starch. The chemicals are safe to use, though you should be aware iodine can stain surfaces or clothing. The containers are resealable, so you can store the color change chemicals to perform the demonstration several times. The explanation of the chemistry behind the reaction is very clear, but I would have preferred if the exact contents of the kit had been stated. It's an excellent demonstration and incredibly simple to perform using the "Think Ink!" kit.

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