Water-Colours for Science

Leonardo. Vol. 15. No. 4. pp. 298-301. 1982 Printed in Great Britain 0024-094X/82/040298-04$03.00/0 Pergamon Press Ltd. WATER-COLOURS FOR SCIENCE Anthony R. Michaelis* Water-colours are amongst the simplest and best tools yet invented by man to give expression to his creative urge. Water, paper and a small box containing a variety of colours are all the essential ingredients to be taken into the desert, to the polar regions, up into a balloon, or down into a cave. Naturally, the result of the finished work will differ, if conceived either as a work of art or as a scientific record; but, after a passage of time. what was intended as one may easily have become the other. 1. The Medium The great characteristic of water-colours is their transparency , best employed when a wash is laid on wet paper, leaving the white of the paper untouched to give the highlights. Thus water-colours can communicate natural events which are passing rapidly, perhaps the shapesof clouds for meteorological studies. Like all man-made colours, the water-colour medium uses the three primaries, yellow, red and blue. First prepared from animal, mineral and vegetable sources, now more stable chemicals are the raw materials. To render any other colour, the user has a variety of ways open. He can either purchase a large number of intermediate hues, in ready-made cakes or tubes, he can place one wash upon another (lasur in German) or alternatively mix two watery solutions of different colours-a technique not highly recommended. Finally he can mix one or more colours on the wet paper itself, letting them run into each other and thus achieve the most delicate and transparent results. Cynics have commented that the size of the paint-box is often inversely proportional to the ability of its user. If the small cubes, the so-called cakes, consisted of nothing but powdered pigment or organic dye, their aqueous solutions, achieved by means of the brush, would never adhere to the paper; when the transfer water evaporated, the pigment would simply be dust and fly away. A binding agent, formerly gum arabic, nowadays a more refined water-soluble adhesive, is therefore mixed with the pigment. When water-colours are used in dry desert countries, it is often advisable to add a small quantity of glycerine to the washwater to avoid all too rapid evaporation; a small drop of glycerine can also be applied directly to the cakes, if they have become dessicated. Exactly the opposite procedure is required when using watercolours in humid tropical regions. Then it becomes advisable to store water-colours in a refrigerator, where the dry air will remove excess moisture from the colours. Even more refined is the use of silica gel to remove water from inside the paint-box. In practice, most users may want to delineate their subjects with either a pencil outline or with ink, preferably Indian ink, so that a subsequent wash will not let the ink run. But of course there is no need to do this, and outlines can be equally effective drawn with brush-strokes. It is well to remember that lines do not exist in nature, only boundaries of different colours. Lines *Science writer and Editor of Interdisciplinary Science Reviews. Spectrum House. Hillview Gardens, London NW4 ZJQ, England. (Received 4 Sept. 1978.) are created by the mental process of abstraction, a very common activity of the scientist. 2. Early History To use water as the vehicle, or the solvent, for pigments and dyes must have been the first idea of the first man who ever thought of recording a coloured image. We therefore find that the paintings inside prehistoric caves were made in this manner and that the same technique was still used when walls were painted to decorate Egyptian tombs. When papyri were coloured, one can almost speak of the first ’water-colours’ and those papyri on which mathematical notations were recorded in colour are no doubt the first use of this medium for scientific purposes. Water-colours also found early use in China, Japan and Korea for colouring fans, umbrellas and lantern shields, whenever they were...