A simple and inexpensive invisible ink system based on red cabbage extracts
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The use of red cabbage (Brassica oleracea var. capitata F. rubra) extract as a pH indicator is a versatile and popular demonstration that is employed by educators in many schools and universities. Previous variations of this demonstration have used red cabbage extracts to prepare paper that changes color when solutions of acid or base are applied as “inks”. In this report, we highlight the ability of red cabbage extracts to function as invisible inks. Colorless solutions are prepared by bleaching anthocyanin extracts with aqueous sodium metabisulfite, and the resulting mixture can then be used to write hidden messages on paper. The invisible messages can be revealed by the addition of citric acid solution, or by using potassium aluminum sulfate (alum) as developers. The demonstration does not require specialist equipment or chemicals, and options to use additional plant sources to prepare the ink are described.
Keiller , L , Patterson , I L J , Stewart , D & Smellie , I 2023 , ' A simple and inexpensive invisible ink system based on red cabbage extracts ' , Journal of Chemical Education , vol. Articles ASAP . https://doi.org/10.1021/acs.jchemed.2c01032
Journal of Chemical Education
Copyright © 2023 The Authors. Published by American Chemical Society and Division of Chemical Education, Inc. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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