Join the American Chemical Society at the Illinois State Fair   —   Springfield, Illinois

THE MYSTERY OF THE BLOODY FINGERPRINT

AMAZE YOUR FRIENDS BY TAKING THEIR BLOOD WITHOUT NEEDLES OR PAIN USING THIS ILLUSION.

What you need:  Goldenrod Paper  -  a source Windex™ with Ammonia A willing participant with a finger

Step 1: Ask for a willing volunteer from your friends to give you a blood sample. Tell them that you promise it will be painless.

Step 2: Tell them you need to clean their finger with a disinfectant (Windex) before you take the sample.

Step 3: Spray their finger with Windex. Make sure to spray their finger with the spray pointing downward toward the ground and away from their face and eyes.

Step 4: Take their wet finger and press it onto the goldenrod paper. The paper will turn bloody red but their finger will remain colorless.

How does it work?

THIS IS AN ILLUSION AND YOU ARE NOT REALLY TAKING BLOOD FROM ANYONE!!! Goldenrod paper contains an indicator. Indicators are materials that change colors in the presence of an acid or base. Goldenrod paper turns red in the presence of a base. The base is the Windex which contains ammonia. The illusion happens when you spray the person’s finger with Windex. The paper turns red as the finger, wet with Windex, comes in contact with the goldenrod paper. The person thinks they have caused the paper to turn red with blood but you know this occurs because of the indicator is reacting with the ammonia in the Windex.  The red color vanishes as the ammonia evaporates in the air, so you can reuse the paper over and over again for awhile. This is a great trick for Halloween.  

WARNING: Never spray Windex toward anyone’s eyes. Never use any needles or pins for this illusion!!!

 

 

----Contributed by Fran Kravitz, Chicago Section