Goldenrod paper is a color change paper that is popular for kid’s science experiments because it’s interesting and non-toxic. Sometimes the paper is available for purchase online, but it’s easy to make goldenrod paper yourself. Once you understand the basics, you can make color change paper in any shade of the rainbow.
How Goldenrod Paper Works
Basically, goldenrod paper is pH paper, much like litmus paper. During the manufacturing process, the paper is dyed with a pH indicator that appears golden yellow (the color of the goldenrod flower) under neutral and acidic conditions. Applying a base to the paper turns it red. The pH indicator in the type of goldenrod paper you buy is a combination of curcumin and Direct Yellow 4. The dye is not soluble in water, but is soluble in ammonia and other basic solutions.
Commercial goldenrod paper displays a wider range of color changes than homemade goldenrod paper. The Direct Yellow 4 dye turns the paper black under highly acidic conditions (like with 3 M hydrochloric acid) and purple-black in an iodine solution.
How to Make Golden Rod Paper
Knowing how commercial goldenrod paper works, it’s easy to make it yourself. Instead of pure curcumin, dye paper using the spice turmeric. Turmeric gets its golden color from curcumin. The turmeric won’t stick to the paper surface if you just sprinkle it on, so soak paper in a mixture of boiling water and turmeric to open the spaces between the cellulose fibers in paper and deposit the pigment.
- Turmeric
- Paper
- Boiling water
The type of paper readily available to most of us is printer paper, which works, but you’ll get a deeper color using a coarser paper, like construction paper. The amount of turmeric and water you use is not critical.
- Mix together turmeric and boiling water in large pan or on a cookie sheet. Stir until the mixture is smooth.
- Soak the paper in the liquid so it’s saturated.
- Remove the paper from the liquid and place it on a paper towel to dry. (Use tongs or wear gloves unless you want yellow fingers.)
- Repeat the process and make as much goldenrod paper as you like.
How to Make Color Change Paper in Any Color
Turmeric is one of many pH indicators found in everyday life. Dyeing paper using other non-toxic indicators from the home or garden expanded the options for color change paper. Soak paper in juice and let it dry. You might need to blend solid produce to get its liquid. Red cabbage juice displays the most colors.
| pH Indicator | Acidic Color | Neutral Color | Basic Color |
|---|---|---|---|
| Beets | Red | Reddish-purple | Purple |
| Blueberries | Red | Purple or green | Green |
| Curry powder | Colorless | Colorless to yellow | Red |
| Grape juice | Red or purple | Red or purple | Green |
| Red apple skin | Orange | Pink to peach | Yellow-green |
| Red cabbage | Orange, red, purple | Blue | Green |
Goldenrod Paper Science Activities
Once you have goldenrod paper, what do you do with it? Here are ideas for fun science activities.
- Draw an invisible message or picture on the paper using a wax crayon. Spritz the paper with window cleaner, ammonia, or a solution of baking soda in water. The message remains yellow, while the paper turns red.
- Dip your hand in household ammonia or a solution of either baking soda or washing soda in water. Make a handprint on the paper. It looks like a bloody handprint on goldenrod paper. This is a popular Halloween science project. Over time, the red hand print fades. Why? Carbon dioxide in air dissolves in the liquid, forming carbonic acid. The pH of the “blood” changes, eventually becoming close enough to neutral that the indicator changes from red back to golden yellow.
- Use goldenrod paper to illustrate chemical changes, pH indicators, and acid-base reactions. Cut strips of goldenrod paper and use them as pH test strips. Test common household acids (yellow), neutral liquids (yellow), and bases (red). Compare these results with colors you get from test strips made using other pH indicators.
- Ask students what they expect happens if you paint the paper using chlorine bleach. Bleach decolorizes curcumin. Knowing this also makes clean-up easier!
Common Household Acids and Bases
Which common household products are good for testing goldenrod paper or other homemade color change paper? Here is a list of common acids and bases in the home.
Acids
- Vinegar
- Lemon juice
- Most fruits
- Citric acid
- Ketchup
- Salsa
- Soft drinks
Neutral
- Water
- Milk (very slightly acidic)
Bases
- Ammonia
- Baking soda in water
- Washing soda in water
- Soapy water
- Toothpaste
References
- Manolova, Y.; Deneva, V.; et al. (November 2014). “The effect of the water on the curcumin tautomerism: a quantitative approach”. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 132: 815–20. doi:10.1016/j.saa.2014.05.096
- Schorr, Donald K.; Campbell, Dean J. (2019). “Demonstration Extensions Based on Color-Changing Goldenrod Paper.” J. Chem. Ed. 96(2): 308-312. doi:10.1021/acs.jchemed.8b00341