Goldenrod Paper Message
Use this special pH paper for some spooky Halloween science
The term goldenrod is typically used to describe a color of paper – golden yellow. However, our goldenrod paper contains a special dye that turns bright red when exposed to solutions that are basic, like ammonia water or washing soda. We'll show you how to use this special color-changing paper to develop a hidden message and make dripping, bleeding paper… complete with your own handprint marked in “blood.” It's a great acid/base lesson for the Halloween season.
- Goldenrod Paper
- Cotton balls
- Ammonia-water solution (household ammonia from the grocery store)
- Candle or clear wax crayon
- Place a piece of Goldenrod Paper on the table. Make sure that the table is clean and the work surface is dry.
- Place a drop of water on one of the corners of the paper. Does anything happen?
- Fill a jar with a small amount of ammonia water. Dip a cotton ball in the ammonia water and wipe it across the top portion of the Goldenrod Paper. Save the bottom half of the paper for step 5. Does anything happen?
- As you continue to wipe designs on the Goldenrod Paper, notice that the paper does not stay red forever. What is causing the paper to change back to yellow?
- Use the old piece of wax candle to write a secret message (such as “Hi!” or “WOW”) across the bottom half of the paper.
- Wipe the cotton ball with ammonia water across the secret message to see what develops.
- Place a piece of Goldenrod Paper on a clean, dry surface.
- Away from the paper, spray your hand with “magic water” (the ammonia-water solution).
- Tell your audience that when you touch the paper you can make it bleed.
- Gently slap your hand down on the Goldenrod Paper… oh no! It's a bleeding handprint!
Your audience won't believe their eyes when you hold up the Goldenrod Paper, dripping with your “bloody” handprint. It's the perfect Halloween experiment.
How Does It Work?
The ammonia on the cotton ball is a base and causes the dye in the special Goldenrod Paper to change color. You probably noticed that the red color fades over time and the paper eventually changes back to its original yellow color. Why? The carbon dioxide gas that is in the air we breathe is slightly on the acidic side of the pH scale. The carbon dioxide reacts with the ammonia on the paper to produce ammonium carbonate, which changes the pH of the paper to neutral (roughly a pH of 7) and the dye changes back to yellow. If you use a stronger base like washing soda, the red message will not disappear with just the carbon dioxide in the air. You will need to use a stronger acid like lemon juice or vinegar to change it from red to yellow. You can also use Goldenrod Paper as inexpensive pH paper to classify safe household products as being either acidic or basic.