{"id":67570,"date":"2026-09-18T04:44:37","date_gmt":"2026-09-17T19:44:37","guid":{"rendered":"https:\/\/phys-edu.net\/wp\/?p=67570"},"modified":"2026-09-18T04:44:37","modified_gmt":"2026-09-17T19:44:37","slug":"moldy-blue-mandarin-turns-deliciously-yellow-the-secret-behind-the-magic-paper-that-amazed-a-kindergarten","status":"publish","type":"post","link":"https:\/\/phys-edu.net\/wp\/?p=67570&lang=en","title":{"rendered":"Moldy Blue Mandarin Turns Deliciously Yellow!? The Secret Behind the “Magic Paper” That Amazed a Kindergarten"},"content":{"rendered":"

I’m Ken Kuwako, a science trainer. Every day is an experiment.<\/strong><\/span><\/p>\n

\u201cTeacher, is this magic paper!?\u201d<\/p>\n

Those amazed voices filled the kindergarten classroom. This year, we launched a Science Show Development Seminar<\/b> at our school, bringing together 20 students who absolutely love science. This time, I visited Sonohara Kindergarten with these students, where we put on a science show for two classes of senior kindergarteners. Today, I’d like to share the star experiment that stole the show.<\/p>\n

The secret is \u201ccolor-changing paper\u201d! Simple to prepare, but full of science<\/h3>\n

To reveal the secret, this magic paper is simply Japanese calligraphy paper soaked in BTB solution<\/b>, an indicator that tells us whether a substance is acidic or alkaline. We added a little baking soda to the BTB solution to make it alkaline, soaked the calligraphy paper in it, and let it dry. The result was bright blue paper. For this event, we prepared about 30 sheets of this \u201cmagic paper.\u201d<\/p>\n

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We also prepared two liquids: water containing citric acid, and water containing baking soda and sodium carbonate. These two liquids were the real secret behind the paper’s magical color changes.<\/p>\n

Showtime! The Doctor and the Great Adventure of the Orange<\/h3>\n

The show began with a little skit. A \u201cdoctor\u201d from the junior high school appeared and spoke to the children.<\/p>\n

Doctor: \u201cI have something I want to show you today! I finally finished it yesterday! It’s magic paper\u2014the \u2018Magic Paper\u2019!\u201d<\/b><\/p>\n

First, we asked the children to draw an orange on the paper with crayons. But because the paper was blue, their finished oranges looked almost like moldy oranges<\/b>. The children looked worried and said things like, \u201cHmm… it kind of looks moldy.\u201d<\/p>\n

That was when the first liquid appeared: citric acid solution. According to the teacher playing the doctor, \u201cIt contains the same ingredient that you find in lemons!\u201d We dipped a brush into the liquid and painted it onto the blue orange.<\/p>\n

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And then\u2014amazing! The paper gradually changed to a vivid yellow<\/b>. The moment the blue, moldy-looking orange suddenly transformed into a juicy, fresh-looking orange, cheers erupted throughout the room. The children\u2019s eyes lit up as they eagerly enjoyed painting their pictures.<\/p>\n