Bleeding Goldenrod Paper – Halloween Science Project

Goldenrod paper is a special paper that drips blood! Really, it’s not blood, just a safe red liquid that resembles it. The paper contains a pH indicator that turns red in the presence of a base. You can use it to demonstrate pH indicators or for a spooky Halloween science project. If you like, write a bloody secret message or create a bloody hand print. 

Bleeding Paper Materials

This project uses a special paper, called color-changing goldenrod paper. As you might guess, it gets its name from its color, which is the golden yellow color of the goldenrod flower. The paper is available at Amazon and some education and craft stores. It’s also easy to make goldenrod paper yourself. Be sure to use either commercial or homemade color change goldenrod paper and not just any yellowish paper. The color change results from alkaline conditions, which you obtain using ammonia, baking soda, laundry detergent, washing soda, or soapy water. Ammonia mixed with water works extremely well, but younger researchers may wish to use baking soda in water, since it is very safe.

• Color-changing goldenrod paper
• Household ammonia or baking soda
• Cotton swabs or cotton balls
• Wax crayon or white candle

Bloody Hand Print

1. Dip your hand in a mixture of household ammonia and water or baking soda and water.
2. Slap your hand onto a sheet of goldenrod paper. See the bloody hand print? If your hand was wet enough, the paper will appear to bleed, too.

Bloody Hidden Message

1. Use a wax crayon or piece of white candle to write a message on the goldenrod paper. The message appears invisible on the paper.
2. Reveal the message (in ‘blood’) by wiping the paper with a cotton ball dipped in ammonia.

How Goldenrod Paper Works

When you buy goldenrod paper, it typically contains an azo dye, such as Direct Yellow #4 or Brilliant Yellow (C₂₆H₂₀N₄O₈S₂). Depending on the specific composition, the paper sometimes darkens at extremely low pH, becoming black or purple. The color change is reversible when pH changes.

Alizarin Yellow R is another azo dye that changes between yellow (below pH 10.1) and red (above pH 12.0).

When you write or draw on the pH indicator paper using ammonia as the base, notice the red color fades after a while. This is because carbon dioxide in the air makes the liquid more acidic. You can play with other bases, such as washing soda, which does not change color in air. For a stronger base, counteract the pH using a common household acid, such as lemon juice or vinegar.

How to Make Goldenrod Paper

The paper is rather expensive, but making it yourself is affordable and easy.

• 4 tablespoons turmeric
• 2 cups boiling water
• White paper
• Cookie sheet or baking pan

1. Mix together the turmeric and boiling water until the mixture is smooth.
2. Place paper into a baking sheet and completely saturate it with the mixture.
3. Remove the paper and set it aside to dry.

Once the paper is dry, use it just like the commercial paper. It is golden yellow under acidic and neutral conditions, but starts turning brown around pH 7.4 and red above pH 9.2.

You have other options besides turmeric. Here is a comprehensive guide for making your own color-changing pH paper, including the classic goldenrod paper, plus other colors!

References

• Lide, David R. (2007). CRC Handbook of Chemistry and Physics (88th ed.). CRC Press. pp. 3–10. ISBN 9780849304880.
• 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
• Ravindran, P. N., ed. (2007). The Genus Curcuma. Boca Raton, FL: Taylor & Francis. p. 244. ISBN 9781420006322.