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20 Minute Labs - Fake Halloween Blood

20 minute labs blood logo | Yellow Scope



halloween kids  | Yellow ScopeHalloween is just around the corner! Maybe you need some  fake blood for your vampire costume? Or maybe you just want to have fun doing some spooky science in your kitchen this weekend.  

In this month's 20 Minute Lab, we'll make costume blood using everyday items from your baking shelf! 

Did you know in old black and white movies that they used to use chocolate syrup for blood? But that won't do in our real world of color!

halloween icons | Yellow ScopeAlso, to make fake blood look real, the liquid needs to be thicker than just red-colored water.

In this experiment, we'll create thick, dark, realistic-looking blood. You'll have all the other trick-or-treaters in awe!

NOTE: If making fake blood is a bit too spooky for your little scientist, check out our Bubbling Brews Experiment!

WHAT YOU’LL NEEDfake blood supplies | Yellow Scope blog

  • 4 ounces water
  • 2 cups powdered sugar
  • 2 tablespoons cocoa powder
  • 0.1 ounces red food coloring (about a third of a typical bottle)
  • blender
  • tablespoon
  • measuring cup
  • clean up towel
  • optional: wooden spoon or spatula (for scraping down the sides of the blender)

NOTE: though this recipe is safe, edible, and can be cleaned up with soapy water, it may stain, so choose clothes that can get messy!


  1. blender | Yellow Scope blogPlace the water in the blender.
  2. Add the powdered sugar, then blend until thoroughly mixed. You may have to stop once or twice to scrape down any sugar that's stuck to the sides.
  3. Add the red food coloring and blend well.
  4. Add the cocoa powder and blend well. Again, scrape down the extra cocoa stuck to the sides.
  5. That's it! You've made a batch of blood!
  6. How you apply your blood will depend on what you need it for, but drizzling it from a spoon works great if you just want it to fall naturally on your skin like this:

fake blood on hand | Yellow Scope blog


What's going on?

water vs molasses | Yellow ScopeWhat makes this fluid different than just using colored water?

All liquids flow, but some flow faster than others. Viscosity is the property of a liquid that describes how fast or slow it will flow. Usually, the thicker the liquid, the more viscous it is and the slower it flows.

Water is NOT very viscous - it flows very well. Think about pouring water out of a bottle - it comes out pretty fast, doesn't it?

Molasses, on the other hand, is much more viscous than water. Molasses flows very slowly - you might even have to use a spoon to get it out of the jar. 

Blood has a viscosity in between water and molasses; it's not as viscous as molasses, but it's about four times more viscous than water. In addition to water, blood is made up of cells and proteins, which make it thicker and more viscous.

For our fake blood recipe, we started with water. To make it thicker, we added powdered sugar and cocoa to imitate the viscosity of real blood. Did you notice that the mixture got thicker when you added the sugar? The cocoa powder also helped to thicken the mixture. In addition, the cocoa powder added a brownish color to make it look more like real blood - which is quite a bit darker than just bright red food coloring!


Let us know what you did. Share your photos and results with us on Facebook, Twitter, Instagram, or send us an email to We love getting your messages!

For more exciting experiments, check out our Yellow Scope Science Kits on the Shop tab of our website!

Chelsea Schuyler
Chelsea Schuyler