Japanese ink: Ancient inspiration to understand colloids

Hands-on learning is often a desirable option when teaching pupils. In the case of organic chemistry, however, hands-on learning can be tricky for a number of safety reasons. Using the example of Japanese ink, Mr Junpei Hayakawa, a science teacher for Nara Prefecture, was able to develop teaching materials that allowed students to understand the basics around colloids and their properties, as well as the use of several characterisation methods. He developed engaging protocols that used the ‘easy’ recipe for Japanese ink (soot as carbon source, glue as protective agent, and water), exploring different sources for carbon and different protective agents, to showcase colloids with different properties.

Communicating complex scientific concepts in ways that are relatable and understandable by pupils or those without a specific science background can be tricky. The scientific concept must be translated into a form that is easily comprehensible, and it can be highly beneficial for the learning process to be hands-on. Hands-on experience and testing of concepts can reinforce learning and relate the theory with an actual application, so it is highly encouraged, especially in science education. Teaching chemistry, however, can be difficult, especially when aiming for this hands-on learning approach.

Educators need to come up with clever yet safe and fully controllable ways to illustrate concepts around inorganic and organic chemistry, and engage pupils using activities that support learning outcomes. On many occasions, teachers rely on real-life, everyday examples to demonstrate various concepts, not only around chemistry, but also touching on physics, engineering and other disciplines. Such examples can include the demonstration of a pump using the concept of a heart as an example, use of enzymes naturally present in fruits such as pineapple to demonstrate the ability to digest gelatine, or the production of carbon dioxide via the bubbling reaction between baking soda and lemon juice, among others.

Introduction to organic chemistry and colloids

Organic chemistry is a branch of chemistry that revolves around the study of carbon and compounds containing carbon in combination with other elements, with examples ranging from fuels to food, and even our body. There are several sub-areas of organic chemistry, depending on the type of substance, the nature of the substance, or other categorisations. Some examples of sub-areas based on type of substance include hydrocarbons (fuels), or enzymes (biological catalysts). Some examples of sub-areas based on the phase of substance include solids (like carbon itself, in the form of coal or diamond), liquids (solvents like acetone or hexane), or gases (such as natural gas). Sub-areas can also emerge when combining substances of different phases, which is the case with colloids, where solid particles are stably dispersed in a liquid phase.

“Japanese ink was used as an inspiration for hands-on-learning relating to the chemistry and properties of protective colloids in schools.”

To further explain this, imagine dropping a pebble in a bucketful of water. The pebble will quickly sink to the bottom due to gravity. However, if you place a handful of sand into a bucketful of water, the time for sand particles to sink will be much longer compared to that for the pebble, and there might even be some tiny particles that will not sink. This is due to the levitation concept, which can partially counteract gravity. Now imagine dropping droplets of olive oil in a glass of water. The olive oil will stay on top of the water body, due to density difference and due to the tendency of oil not to dissolve in water (hydrophobicity). If, however, we introduce mixing, then tiny oil droplets will be incorporated into the water body. This is due to the mechanical disruption of the two phases.

There are cases where we can have a stable mixture of particles in liquid, or two seemingly unmergeable phases, in such a way that a consistent new phase emerges, that being a colloid. The stability of this ‘unnatural’ phase depends on the ability to overcome the natural separation of unmergeable phases, which is governed by physical and chemical principles such as gravity or surface tension. This can be achieved by ensuring that gravity is not overpowering levitation, or through use of other substances that act as a protective layer around a substance that should not be able to merge within the bulk substance. There are numerous examples of c in our everyday life, such as mayonnaise (suspension of oil in water with the help of egg), jelly (suspension of fruit in water with the help of pectin), butter (suspension of water droplets in oil) and even whipped cream (suspension of air bubbles in milk).

Japanese ink as colloid representative for hands-on learning

Examples of colloids are not limited only to food; they can extend to many other areas. Other examples of colloids include coloured glass (suspension of metal particles in melted clear glass), fog (suspension of liquid droplets in air), and even materials developed hundreds of years ago and still used today in some cultures, such as Japanese ink. Japanese ink is a colloid suspension of soot in water with the help of glue. Soot, carbon particles produced from the incomplete burning of organics (think as an example of the black powder collected in fireplaces), does not mix with water, due to the hydrophobic nature of soot. However, when we include a ‘helper’ into the mixture, things change.

In the case of Japanese ink, the helper is glue. The role of glue is to ‘balance’ the hydrophobic nature of soot and facilitate its dispersion in water in a stable manner, creating a protective environment around the soot. The way this is done is through the structure of glue, which is based on proteinaceous substances with a hydrophobic and a hydrophilic end. To visualise the structure of Japanese ink we could say that every glue particle has a hydrophobic and a hydrophilic end, and that a soot particle is surrounded by glue particles with their hydrophobic ends towards the soot and the hydrophilic ends towards the bulk of water, creating a protective layer which connects the two phases. In this way, glue helps overcome the chemical barrier of opposite charges between soot and water, creating a stable dispersion which belongs in the category of protective colloids.

Recently, Japanese ink was used as an inspiration for hands-on-learning of the chemistry and properties of protective colloids in schools. The use of Japanese ink for educational purposes was showcased by Mr Junpei Hayakawa, a science teacher for Nara Prefecture. Until 2013, Mr Hayakawa worked as a Research Fellow for the Japan Society for the Promotion of Science (DC1), before starting his career as a science teacher at Nara Prefectural Sakurai Senior High School, Sakurai, Japan. In 2016 he moved to Sango, Japan, as a Science Teacher at Nara Prefectural Seiwaseiryo Senior High School. His recent publication on the interface of material characterisation and chemistry education explored the use of various carbon materials to produce Japanese inks and the use of these inks as teaching materials around protective colloids and their characterisation.

Not just soot for Japanese ink

Mr Hayakawa used several other carbon sources besides soot for Japanese ink production, such as carbon nanotubes, fullerene, graphite, and graphene, with inks produced from each source examined for different properties of protective colloids. The synthesis method of the inks is quite straightforward and easily replicated in a classroom, posing low hazards for students, hence making the incorporation of this teaching activity in schools very attractive.

With only three raw materials (water, carbon source, and a helper substance) and easy to follow mixing steps, students are able to create their own Japanese inks. The first point of learning was introduced with the presence or absence of the helper (glue), resulting in completely different outcomes, an unmixed solution with two phases, or a consistent solution, the colloid. The combination of carbon source and the helper substance (glue, gelatine, agar) can lead to different end results, allowing students to explore a wider range of protective colloids, their properties, and characterisation methods.

“Mr Hayakawa helped students improve their understanding not only of protective colloids, but also of characterisation methods.”

Hands-on-learning using protective colloids

Colloid chemistry includes some complex phenomena, such as the Tyndall phenomenon and Brownian motion. The first is related to visibility of a light ray due to the presence of particles that can scatter the light. The second represents the random, uncontrolled movement of particles present in a solution, when colliding with each other.

Using the Japanese ink colloid example, Mr Hayakawa was able to design teaching aids that would help students understand these phenomena, by, for example, shining laser pointers through a colloid sample, or by observing the colloid under a microscope in suitable dilution so that particles and their movement could be observed.

Mr Hayakawa did not stop there though. By cleverly designing teaching aids putting Japanese ink at the centre of attention, he was able to help students improve their understanding not only around protective colloids and their complex properties, but also around characterisation methods, such as use of microscopes or spectrophotometry. The use of traditional, household items for educational purposes can be highly engaging. It is an easy way to achieve hands-on learning, as it connects theory with application and does not require specialised raw materials or equipment.

References

• Ishido K, Hayakawa J, (2021) Preparation and Characterization of Japanese Ink-Inspired Aqueous Dispersions of Carbon Materials with the Help of Glue as Colloid Chemistry Teaching Aid. J Chem Educ, 98, 1381–1388.

Research Objectives

Mr Junpei Hayakawa uses Japanese ink as an ancient inspiration to teach children about the fundamental properties of colloid chemistry.

Funding

Mr Hayakawa would like to thank the following for their research grants:

• Shimonaka Memorial Foundation
• Takeda Science Foundation
• Nakatani Foundation
• Japan Society for the Promotion of Science (Project No. 17H00293)
• National Research and Development Agency (a programme for promoting science and research activities of junior and senior high school students).

Collaborators

Mr Hayakawa would like to thank:

• Mr Kaito Ishido, Mr Kazuki Nakamura, Mr Koki Taniyamma, Mr Kento Fujita, Mr Kazuya Nakatani, Ms Rui Ito, Ms Airi Uzawa, Mr Masato Takada, Ms Fuwa Yoshioka and Ms Yuri Nakagawa, who are the co-researchers of Science Team, Seiwaseiryo.
• The Technical Team, Technology Development Department, Nitta Gelatin Co Ltd, who provided instructions on gelatine.
• Prof Dr Tomoyuki Yatsuhasi and Prof Dr Satoshi Shinoda of the Graduate School of Science, Osaka City University, who supported the research.
• Prof Masashi Ando of the Department of Fisheries, Faculty of Agriculture, Kinki University, who measured the composition of glue amino acids.
• Mr Tatsuro Hayashi of the Nara Prefectural Industrial Promotion Center, who helped with resistivity measurements.
• Mr Tsuyoshi Yamamoto and Mr Kenichi Murakami of the Nara Prefectural Board of Education and Prof Yutaka Wada of Nara University of Education, who provided support during busy hours.
• Ms Victoria Eichbauer for English proofreading.

Bio

After gaining his Bachelors in 2009, and his MSc in chemistry in 2011, both at Osaka University, Junpei worked as a research fellow at the Japan Society for the Promotion of Science (DC1) between 2011 and 2013. Since then he has been working as a science teacher, and currently teaches for Nara Prefecture.

Contact
4 Chome-7-1 Shigigaoka, Sango, Ikoma District, Nara 636-0813, Japan

E: [email protected]
W: www.e-net.nara.jp/hs/seiwaseiryo

Japanese ink: Ancient inspiration to understand colloids