Fake Blood made Scientific
With Halloween just around the corner, bloody scenes are just a block away. Whether it is dripping vampire teeth, a bloody nose, or a leaky bandage, fake blood is sure to bring characters to life, so to speak.
While chocolate syrup might make convincing fake blood on black-and-white photography, it is not passable for real-life encounters or color film. In this activity, science helps you engineer your latest product: good-looking (and tasty!) fake blood.
This activity is not appropriate for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.
Several physical quantities, like the viscosity (or how it slowly or quickly it runs), and color determine the look of a fluid.
Viscosity is a measure of the thickness and stickiness of a fluid. It quantifies its resistance to flow. Together with its density, the viscosity of blood determines how blood flows through blood vessels or how it runs down your leg, finger or arm after a cut. At normal body temperature (37 degrees Celsius), blood is four times more viscous than water, but only slightly denser. As a result, it flows more slowly and it is stickier than water. Corn syrup or honey, on the other hand, are far more viscous (more than thousand times) than blood. They are also denser. Diluting these with water will reduce their viscosity.
To get the color of human blood right seems easy, it is always red. The red color comes from red blood cells, which carry oxygen from the lungs to tissues and organs. They turn bright red when carrying oxygen, and turn a darker, blue hue after delivering the oxygen to cells around the body.
Clotting blood (or coagulating blood) has a different look. The chemical reactions taking place when blood clots form make it look darker. It is also thicker and more gel-like.
Now that you know a little about what blood looks like, you are better equipped to create fake blood.
Extra: To mimic dried blood, add more chocolate syrup and make it thicker, as clotting blood has a darker red color with a brown hue, and is thicker, more gel-like. You can also add a spoon of coffee grounds to mimic the scaly appearance of the crust on healing wounds.
Extra: Test other ingredients you find around the kitchen for their ability to mimic blood. See how they flow, how they can add to the color. Some ideas are ketchup, red beet juice, maple syrup and peanut butter.
Observations and Results
The main ingredients of your final recipe probably consisted of corn syrup diluted with water and thickened with flour. This particular mixture resembles the flow of blood quite well, as it has a similar viscosity, or resistance to flow. You probably noticed the red-colored corn syrup is too viscous, it flows too slowly and leaves a thick trace behind. The red water was way too runny and left almost no trace on the board. The flour helped to thicken the mixture, but did not get the viscosity quite right yet.
The recipe to obtain the most realistic color depends on the exact hue of food coloring used. Most often, a tiny bit of blue yields a more realistic look. The brown from chocolate syrup often provides a good addition in color, especially if you want to mimic blood that is low in oxygen. It also reduces the transparency of the fake blood.
Now that you have some experience, you might just find more great recipes using other food items available in your kitchen. Enjoy!
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Sabine De Brabandere, PhD, Science Buddies
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