©Lin Yangchen

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The coconut definitive observes a tradition as old as the postage stamp itself: that of issuing the unit denomination in black. Black, by definition, emits no electromagnetic radiation at any wavelength; it somehow feels reasonable for the first denomination to have no colour. The real reason was probably more pragmatic: black ink was common and easy to keep consistent.

Many other definitive issues have followed the example of the Penny Black of 1840 (left), such as the 1934 Hindenburg definitive issued by the Third Reich under Adolf Hitler, on swastika-watermarked paper (right). The Penny Black itself was changed to red soon after it was released, so that more robust black postmarks could be used. Yet the tradition of black stamps persisted.

Black shades tend to be consistent, but variations have been catalogued for the BMA blacks. The main constituent of black ink is commonly carbon, but subtle differences in the composition of other chemical elements present may give rise to equally subtle shade differences (see Lyons 2017).

The black look is given a mutagenic transformation by printing it on green paper in the enthralling 50 cents. It reminds the author of the radioactive γ-emitting radium-226 used on luminescent clock faces in the past. Perhaps this gave the stamp an expensive look without having to use different colours for the key and duty plates. But this made it prone to forgery.

Grey ink was probably made by mixing black and white pigments, both of which were probably readily available. In modern times, grey ink is used in printers to modulate greyscale and coloured tones, and (digitally) as grey text on websites to reduce eye strain.

Many denominations fluctuated in shade over the long production run of the coconut definitive (see Stanway 2009). The Crown Agents put in almost 200 orders for coconut definitives in the post-war period. Pale shades (e.g. above right) are thought to be the consequence of cost-cutting ink dilution.

Brown has been found to be people's least favourite colour, but it naturally exudes a down-to-earth charm not felt in other colours. Brown was a relatively consistent colour in the coconut definitive throughout its tenure, with only slight fluctuations. This suggests that the ink was very simple in composition, perhaps containing only a single pigment. Yet De La Rue (c. 1950) stated that brown was one of the most difficult colours to make, without elaborating.

The energy-dispersive X-ray spectrum of a Selangor 4-cent brown indicates the use of iron (III) oxide (Fe2O3) pigment on a calcium carbonate coating seasoned with a pinch of aluminium silicate (kaolin).

These stamps, originally of a similar shade, illustrate the well-known tendency of mauveine to wash out and permeate through the paper. The left half of the composite image of the stamp at upper right shows the hallmark “volcanic lava” fluorescence of aniline-based inks under 365 nm longwave ultraviolet radiation. See BMA $5 for more purple and mauve shades.

De La Rue formulated some of their own inks from natural dyes. They also used synthetic dyes imported from the German chemical industry (Fernbank 2013). War made the latter difficult.

An article in the De La Rue Journal (c. 1950) gives a fascinating glimpse, with photographs, of the ink-making department at their Leeds plant. They nicknamed the department “Rainbow Corner” or “Rainbow Room”. Of the men who worked there, “their overalls are gaily daubed with streaks of bright red, yellow and blue, and their working day is occupied with the problems of colour, tone and texture.” Of course, Bunhill Row too had an ink-mixing section. Samples of raw materials were tested at Bunhill Row before being sent to Leeds. The article seems to pertain to ink for banknotes, but the protocol for stamps should not have been too different if perhaps less stringent.

A separate ink testing and formulation department first worked out the pigments and proportions needed for a desired colour. The experimental ink was spread out on a lithographic stone and transferred to paper for examination, and the trial and error was repeated until the right shade was obtained. This could take up to two days. They also tested the ink’s drying speed. According to De La Rue, a good ink took about 24 hours to dry completely—no more, no less.

Once the recipe was approved, the ink-making department took over. Pigments were weighed out in a big pail on a weighing scale big enough for a man to stand on, but the measured weights had to be accurate to 0.25 oz (about 7 grammes). A high-speed agitation machine then mixed the pigments with linseed oil varnish which acted as a liquid binding medium. The mixture was passed several times through a mill to break down and disperse the pigment particles until the suspension became “thick, and smooth as velvet”. Samples were taken to check against the original specimen from the formulation department. The ink was then dispensed into drums about a metre tall and 40 cm in diameter (gauged visually by me from a photograph in the article) to send over to the printing department.

After use, the drums were scraped and washed before being refilled. They were stacked in a cage and lowered into a tank of hot caustic soda (sodium hydroxide).


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