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Color-Changing Thermochromic Pumpkin

It works like magic: touch the pumpkin and the handprint left behind changes from one color to another before your eyes. Our secret? An ingredient called "thermochromic pigment."

color changing thermochromic pumpkin

Photography: Peter Ardito

Source: Martha Stewart

Introduction

This idea comes from Digital Editor Alexandra Churchill. It changes color due to a change in temperature, which is a property called "thermochromism" and it can be applied on a number of surfaces including pumpkins.  The fine, colored powder — also known as "thermochromic pigment" — changes to a clear powder when heated to 77 degrees. The process is also reversible: when it gets cold, the pigment returns to its original color. This specialty pigment can be combined with almost any clear binder such as glue, varnishes, or resins to produce a paint. However, it is recommended to use a clear binder with neutral PH 7; an acidic or alkaline binder can destroy the fine microstructure of the pigment.

 

Tip: To extend the life of your color-changing pumpkin, we recommend keeping it in a cool environment out of direct sunlight. Overexposure to light and the overuse of solvents may cause expedited fading.

materials

  • Black pumpkin
  • Thermochromic pigment (Pictured: Black to pink, $19.99 for 10 g., amazon.com)
  • Clear sealant (Pictured: Mod Podge matte-finish sealant, $8.99 for 16 oz., michaels.com)
  • Paintbrush
  • Small mixing bowl
  • Measuring spoons
  • Wooden skewer

steps

  1. Mix spoonfuls of thermochromic pigment into sealant, following a 1-to-2 ratio of pigment to sealant. Use a wooden skewer to stir until fully combined and clumps are dissolved.
    color changing thermochromic pumpkin step 1
  2. Working in sections and using a paintbrush, apply an even coat of thermochromic mixture onto the pumpkin; let dry. Repeat for 2 to 3 coats.

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