A Simple and Inexpensive Invisible Ink System Based on Red Cabbage Extracts

Red onion, Allium cepa, juice can dye a cloth sample green upon the addition of alum, aluminum potassium sulfate, and this sample can turn red when subjected to an acidic solution. When the red-colored sample is washed with a neutral or alkaline aqueous solution, its color turns green again. These experiments illustrate color changes that can be used in activities to aid understanding of metal coordination and acid−base chemistry. The addition of alum (aluminum ions) to red onion juice leads to the formation of a coordination complex causing the green color and generating a pH-responsive dye. This paper introduces a series of experiments, such as the use of a simple and low-cost method to dye a cloth sample green using red onion skin and alum, color variation of the cloth sample between green and red by adding readily available acids or bases, and use of commercially available chemical reagents to separately dye samples yellow, blue, and green. By conducting these experiments, first-year undergraduate students in the engineering faculty could reinforce their knowledge they had learned in the classroom through practical experience.

Section: Introductionmentioning

confidence: 99%

Dyeing Cloth Green Using Red Onion Skin: A pH-Responsive Dye and Aluminum-Ion Complex

Kajiya

2024

“…This phenomenon, which Heines called “vegetable chameleon”, is essentially the ability of vegetable extracts to alter their color. Anthocyanins, a class of natural pigments exhibiting colors ranging from blue to purple to red, exist in many common fruits, vegetables, and flowers, such as red cabbage, black and red grapes, blueberries, blackberries, eggplants, butterfly pea flowers, roses, Hibiscus sabdariffa , and black soybeans. − Among these, red cabbage has attracted the most attention in the literature. , In recent decades, the literature has focused on how to create and utilize natural indicators, ,− with only a few referencing juices that are readily available in local markets as potential indicators. Curcumin, a pigment found in turmeric, has been identified as one such indicator. ,− These pH-sensitive pigments can be used to perform both simple and complex experiments.…”

Section: Introductionmentioning

confidence: 99%

“…These include determining the pH of unknown solutions, indicating the end point of acid–base titrations, examining chemical equilibria, investigating complex solutions, studying organic molecules, and analyzing homemade sports drinks . Beyond these applications, these pigments can be used in art-related activities, such as creating messages in invisible ink , and painting color-responsive pictures. , When immobilized in a biopolymer matrix, these edible natural indicators make activities even more captivating for students …”

Section: Introductionmentioning

confidence: 99%

“…8−12 Among these, red cabbage has attracted the most attention in the literature. 13,14 In recent decades, the literature has focused on how to create and utilize natural indicators, 10,15−17 with only a few referencing juices that are readily available in local markets as potential indicators. Curcumin, a pigment found in turmeric, has been identified as one such indicator.…”

Section: ■ Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Development of Acid–Base Indicators from Natural Pigments in Agar Gel

Im,

Iwayama,

Osa

2023

Teaching chemistry necessitates hands-on activities to help students deeply understand chemistry concepts and relate scientific principles to daily life. However, constraints in accessing laboratory equipment and materials pose significant challenges for educators in conducting experiments. This paper proposes the development of a pH indicator gel derived from natural plants and juices to enhance the teaching of acid−base topics. The aim is to foster interest and inquiry in students through the predict− observe−explain (POE) strategy. The pH indicator gel was formulated by combining agar gel with various natural indicators and immersing it in different buffer solutions with pH values ranging from 2 to 12. The resultant color changes in the pH indicator gels were compared to the colors of reference solutions spanning the same pH range. Experimental results demonstrated that the gel modified its color in a manner akin to the color change exhibited by the corresponding extract indicator in the buffer solutions across the entire pH range. Moreover, the agar gel was able to be reused multiple times while continuing to display alternating color changes in response to the pH of the solution. The pH indicator gel was utilized in teaching acid−base topics to a group of 24 student teachers in Cambodia. This hands-on activity stimulated interest and curiosity in the student teachers, leading to more engaged observations during the experiment. Feedback from these student teachers highlighted that the pH indicator gel was an effective teaching aid for conveying acid−base concepts and helped boost their engagement in laboratory experiments.

Exploring Waste Management with Art Media in the Laboratory: Pigments, Inks, and Paints from Dye Waste

Silverman

2024

As chemical and material wastes have harmful effects on both human and environmental health, waste management is an essential component of climate action. To educate students about core green chemistry principles, it is necessary to teach and practice waste management strategies in the laboratory. Following a previously described laboratory exercise where students use natural feedstocks to tie-dye fabric, this follow-up exercise focuses on students upcycling waste dye and mordant baths into pigment, inks, and paints and evaluating their chemical and material properties and applications. The exercise has students generate, handle, store, use, and properly dispose of waste feedstocks and products while creating biobased art media. It expands on the first exercise exploring the use of reagents from renewable resources to create waste-derived versions of historical iron gall ink formulations. These waste-based art media are then analyzed, distinguishing optical, textural, and drying properties using the Munsell Color System and a texture wheel. Students iteratively formulate media to target applications including writing, printing, and painting. The exercise connects the practice of waste management and the explores the relationships between material composition, function, and application. The exercise both educates students on waste management strategies and reduces the amount of waste generated during laboratory classes. By circularizing materials in the teaching laboratory, students and educators foster an increasingly sustainable and circular economy.