A Science Show Smash Hit! Find the Perfect Formula for Elephant Toothpaste!

Hi, I’m Ken Kuwako, your Science Trainer. Every day is an experiment!

【This article is also available on my radio show!】

Have you ever heard of the experiment called Elephant’s Toothpaste? Once the reaction starts, a massive, fluffy fountain of foam bursts out, looking just like a giant tube of toothpaste being squeezed! It’s a high-impact experiment that’s a huge hit in science classrooms and live shows. Recently, I teamed up with my students to give it a try. Check out the video below to see the explosive results!

To pull off a successful science show, I spent some time figuring out the perfect “recipe”—one that produces maximum foam while staying safe. Hydrogen peroxide is constantly breaking down into oxygen and water, which is why we keep it in the fridge. However, without a little help, this reaction is incredibly slow. By adding potassium iodide to the hydrogen peroxide, we trigger a rapid release of oxygen, creating a mountain of bubbles in an instant. The potassium iodide acts as a catalyst, kickstarting the decomposition process all at once.

Here is the chemical equation for the reaction:

Source: Wikipedia

The size and intensity of the foam depend on the concentration and amount of hydrogen peroxide used. Higher concentrations lead to faster, more dramatic reactions. However, if the reaction is too violent, it can be hard to control—finding that perfect balance is the tricky part! We always conduct these tests with safety as our top priority. It’s also worth noting that this is an exothermic reaction; if you touch the flask or the foam afterward, you’ll feel a distinct warmth. Beyond the visual spectacle, it’s a fantastic way to learn about reaction heat and catalysts.

Experimental Methods

I tested three different variations to see how the results changed.

1. 50mL Hydrogen Peroxide + 3 tbsp Potassium Iodide (dissolved in 50mL warm water)

First, I poured 50mL of hydrogen peroxide into a 500mL Erlenmeyer flask, adding a dash of dish soap and some food coloring for effect. I placed the flask inside a plastic bin and then added the potassium iodide solution (3 tablespoons dissolved in water).

The moment the potassium iodide hits the liquid, oxygen is released so rapidly that the dish soap captures it into a massive structure of bubbles.

With 50mL, the foam filled up the bin nicely. The final volume of foam is directly tied to how much hydrogen peroxide you start with.

Reference: Using Solid Potassium Iodide

When I added the potassium iodide as a solid powder instead of a solution, the reaction looked more like “snake fireworks.” It was much slower, allowing us to observe a long, steady crawl of foam.

A word of caution: if you do this without dish soap, the reaction is violent and the solution can splash everywhere. I also tried a mini-version using just 5mL of hydrogen peroxide in a graduated cylinder. After the reaction, I lowered a glowing wooden splint into the cylinder, and it burst back into flames—proving that the gas being produced was indeed pure oxygen!

2. 200mL Hydrogen Peroxide + 6 tbsp Potassium Iodide (dissolved in 50mL warm water)

Next, I scaled things up. 200mL of hydrogen peroxide paired with a solution of 6 tablespoons of potassium iodide. Here is what happened:

200mL Hydrogen Peroxide

The foam overflowed and covered the entire desk!

This felt like the “Golden Ratio” for a great visual, though I think I used slightly too much water to dissolve the potassium iodide.

3. 200mL Hydrogen Peroxide + 6 tbsp Potassium Iodide (dissolved in 30mL warm water)

Finally, I tried the same 200mL of hydrogen peroxide but concentrated the catalyst by using only 30mL of warm water for the potassium iodide.

Another desk-engulfing success!

For those curious, the dish soap I used was “Kyukyutto” (a popular Japanese brand).

A very important safety note: while weak hydrogen peroxide is sold as a common antiseptic (Oxydol), high-concentration hydrogen peroxide is dangerous. It is corrosive and can cause chemical burns. Even the foam looks tempting to touch, but please don’t! It will turn your skin white and cause a painful stinging sensation that lasts all day. Always wear gloves, a lab coat, and safety goggles. Cleanup should always be handled by the instructor. I actually accidentally touched some during the cleanup, and my skin turned white immediately. Stay safe and keep your distance from the foam!

This is what happens when you touch it—my own skin after an accidental “human experiment.” The stinging lasted for quite a while. Click here for the explanatory slides created by our Science Club! It’s a great resource.

Contact & More

Let’s make the wonders of science a part of your daily life! I’ve put together plenty of fun experiments and tips you can try at home. Feel free to explore!
・My book “Science Notebook” is now available. Details here.
・Learn more about me, Ken Kuwako, here.
・For inquiries (writing, speaking, workshops, TV supervision, etc.), click here.
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Check out my experiment videos on the Science Material Channel!

３月のイチオシ実験！

• 押し花を作ろう！：梅や桜の花の押し花を作ってみましょう。特別なケースに入れると、長く保存できて、しおりにもなります。

テレビ番組・科学監修等のお知らせ

• 「月曜から夜更かし」（日本テレビ）にて科学監修・出演しました。
• 2月27日放送予定「チコちゃんに叱られる」（NHK）の科学監修しました。

書籍のお知らせ

• 1/27 『見えない力と遊ぼう！電気・磁石・熱の実験』（工学社）を執筆しました。
• サクセス15 ２月号にて「浸透圧」に関する科学記事を執筆しました。
• 『大人のための高校物理復習帳』（講談社）…一般向けに日常の物理について公式を元に紐解きました。特設サイトでは実験を多数紹介しています。※増刷がかかり６刷となりました（2026/02/01）
• 『きめる!共通テスト 物理基礎 改訂版』（学研）…　高校物理の参考書です。イラストを多くしてイメージが持てるように描きました。授業についていけない、物理が苦手、そんな生徒におすすめです。特設サイトはこちら。

講師・ショー・その他お知らせ

• 3/20（金）　日本理科教育学会オンライン全国大会2026「慣性の法則の概念形成を目指した探究的な学びの実践」について発表します。B会場 第３セッション： 学習指導・教材（中学校）③　11:20-12:20
• 7/18（土）　教員向け実験講習会「ナリカカサイエンスアカデミー」の講師をします。お会いしましょう。
• 10/10（土）　秘密兵器「帯電ガン」が炸裂！ビリビリ！ドキドキ！静電気サイエンスショー＠千葉市科学フェスタ（午後予定）
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• 楽しい実験…お子さんと一緒に夢中になれるイチオシの科学実験を多数紹介しています。また、高校物理の理解を深めるための動画教材も用意しました。
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