Clear bubbles are a lot of fun, but you can make colored soap bubbles, too. Here’s a recipe for pink or blue colored bubbles, based on disappearing ink (a type of acid-base indicator), so the bubbles won’t stain surfaces when they land.
Colored Bubble Materials
- Liquid Dishwashing Detergent (or other detergent)
- Water
- or Commercial Bubble Solution
- Sodium Hydroxide
- Phenolphthalein
- Thymolphthalein
Phenolphthalein and thymolphthalein are two pH indicators. They color the bubbles. Sodium hydroxide is a strong base. It adjusts the pH of the bubble solution so the pH indicators appear colored rather than colorless.
Colored Bubble Instructions
- If you don’t have bubble solution, make your own by mixing 1/2 cup (500 mL) liquid dishwater detergent, 4-1/2 cups (4.5 L) water, and 4 tablespoons glycerin (60 mL).
- Add the sodium hydroxide and indicator to the bubble solution. For 1 liter (~4 cups) of pink bubble solution, mix about 10 grams (1-1/2 to 2 teaspoons) phenolphthalein and 2-2.5 grams sodium hydroxide (about a half teaspoon) into a liter of bubble solution. For blue bubble solution, you want 10 grams of thymolphthalein and ~2 grams sodium hydroxide. You may find it necessary to dissolve the indicator in a small amount of alcohol before mixing it with the bubble solution.
- Alternatively, if you have it, use pre-made indicator solution, adding the sodium hydroxide to the indicator rather than diluting with water. Just mix the indicator and sodium hydroxide with bubble solution.
- You’ve essentially made disappearing ink bubbles. When the bubble lands, you make the color vanish by blowing on it or rubbing the spot (reacting the liquid with air). To make the spot disappear even more quickly, spritz a little club soda onto the area. Carbon dioxide in air or carbonic acid in club soda raise the pH of the solution, making the indicator colorless.
- Another option for making colored soap bubbles is mixing disappearing ink (from a toy store or magic shop) directly with bubble solution. This product contains the same dye solution (phenolphthalein for pink/red or thymolphthalein for blue).
Colored Bubble Safety Information
- Please don’t drink the bubble solution! Store unused bubble solution in a sealed container or dispose of it by pouring it down the drain.
- These are bubbles intended for ‘blowing bubbles’, not for bathing.
- Sodium hydroxide is a strong base. Avoid direct contact with this ingredient. If you do get some on your hands, rinse them immediately with water.
- Making color-change bubbles is just as easy as making disappearing ink bubbles. Phenolphthalein and thymolphthalein change from red or blue, respectively, to colorless when the pH drops to around 10. Control pH using common household acids and bases, such as club soda or vinegar (acids) and dishwashing liquid or baking soda (bases).
References
- Haney, Mike (2009). “Exclusive: Colored Bubbles Have Landed (and Popped and Vanished) | Popular Science”. Popsci.com.
- MacRakis, Kristie; Bell, Elizabeth K.; Perry, Dale L.; Sweeder, Ryan D. (2012). “Invisible Ink Revealed: Concept, Context, and Chemical Principles of “Cold War” Writing”. Journal of Chemical Education. 89 (4): 529–532. doi:10.1021/ed2003252