1. Why the Sandbox Inventor Was Not the Father of Kindergarten
In the corner of a schoolyard, you can crouch down and scoop sand to build mountains and tunnels. It is tempting to think that the person who started kindergartens must have invented this sandbox. Friedrich Fröbel, a German educator considered a pioneer of kindergarten education, spoke about the significance of playing with clay and sand. Yet, according to a paper by Hiroyuki Kasama of Hokkaido University of Education, Fröbel did not come up with the idea of a "sandbox" as a play facility filled with sand in a designated area [1]. Playing with sand and creating a specific place for it are two different concepts. So, where was the sandbox actually born?
2. The First Sand Play Place: A Sand Mountain in a Berlin Park in 1850
The online encyclopedia Encyclopedia.com cites a sand mountain in Berlin in 1850 as the first example of providing sand for children's play in a public place. In the park, a pile of sand called "Sandberg" (sand mountain) was constructed [3]. This sand mountain crossed the ocean. It is said that Dr. Marie Zakrzewska saw children playing on the sand mountain in a Berlin park and brought the idea to the United States. Eventually, sand was piled in the garden of a church in Boston, starting the "sand garden," where children dug with small shovels and made sand pies [3][4]. Museums and encyclopedias state that this began in 1885. However, some materials say Dr. Zakrzewska visited Berlin in 1884, so we can say it started in the "mid-1880s" [4]. The starting point of the sandbox was not a kindergarten classroom, but a city park. When did Japanese children start playing in sandboxes?
3. Why Early Japanese Kindergartens Used Indoor Play Materials Instead of Sand
The first national kindergarten in Japan, the Tokyo Women's Normal School Affiliated Kindergarten, was established in 1876. According to Mr. Kasama's paper, the school's floor plan did not include a sandbox [1]. Childcare in the Meiji era centered on structured play using indoor educational play materials (Enbutsu), such as building blocks. Outdoor play equipment was rare [2]. An early example is said to be a kindergarten in Okayama. The school's commemorative history notes that sandboxes and swings were set up in the 1880s (Meiji 20s). However, since this is the school's own account, we cannot definitively say it was the first sandbox in Japan. Sandboxes generally began to appear in kindergartens in the 1900s (Meiji 40s) [1]. In 1912 (Taisho 1), educator Sozo Kurahashi introduced the sandbox at Edo-bori Kindergarten in Osaka and individual sandboxes in the magazine "Women and Children." He wrote that "the educational value of the sandbox goes without saying" [2]. By this time, the benefits of sandboxes were already taken for granted. Why was the sandbox chosen as a play area outside the classroom?
4. Why Sandboxes Allow Many Kinds of Play
A slide is for sliding, and a swing is for swinging. Their uses are almost fixed. A sandbox simply has sand piled in it. Hiroyuki Kasama observed that this "open space" and the simple material of sand, which is easy to change shape, allow for diverse play by the children themselves [1]. This is a researcher's perspective, not a scientifically proven fact. The Strong National Museum of Play in the United States offers a similar view. The museum connects sand's texture with learning through the senses, an idea associated with Fröbel, Montessori, and Piaget. The museum notes that sand play leads to math and science experiences, such as testing volume and quantity by filling containers, as well as cooperation and free play [4]. The encyclopedia notes that psychologist G. Stanley Hall emphasized the value of symbolic and social learning [3]. The property of sand being easy to shape changes greatly with one trick: water.
5. Why Sand Crumbles When It Has Too Little or Too Much Water
Dry sand flows freely. But when you mix in a little water, it hardens, allowing you to build mountains and tunnels. A 2019 study on sand crab burrows on Japanese coasts reported that water bridges form between sand grains, acting like cement to bind them together [5]. It is important to note that more water is not always better. If there is too little water, there are not enough bridges. If there is too much water, it can submerge the sand and make it collapse. Experiments have confirmed that structures like tunnels are maintained within a specific range of moisture content [5]. The amount of water also matters when building tunnels in sandbox sand. How can you find that range with your own hands?
6. Experiment: How Does the Amount of Water Change Sand Mountains and Tunnels?
With an adult, try changing the amount of water in a place where you can use sand and water. Prepare several cups of sand, mix each with 0, 1, 2... teaspoons of water, and build mountains separately. Look for the amount of water that makes the highest mountain. You can verify with your own eyes if there is a range where it collapses if there is too little or too much water. Results differ if conditions change, which is also interesting. Wash your hands after playing in the sandbox. The Ministry of Education, Culture, Sports, Science and Technology's notice, "School Environment Sanitation Standards," sets cleanliness standards for schools, stating that "playgrounds, sandboxes, etc., must be clean and free of garbage and animal waste" [6]. This standard does not specify how often sand should be replaced. If you want to learn more, Mr. Kasama's papers are available in Japanese [1][2]. You can also look up how Kurahashi wrote the Japanese word sunaba (sandbox) in Kurahashi's article.