Malaya stamp printing paper - Lin Yangchen
©Lin Yangchen


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In the early 20th century, the Crown Agents specified that paper for letterpressed stamps should be mainly rag (Faux 1986), which was highly durable and absorbed ink well. After World War II, the Crown Agents and the printers agreed on a composition of 80% rag, which would give a strong paper (Faux 1986, Glazer 2004). Rags and textile production waste made up much of the fibre supply in the 1940s and 1950s (Tullis Russell 1950). The remaining 20% of the paper comprised sulphite-treated softwood pulp, esparto grass and a plethora of chemical additives (Glazer 2004). The sulphite process removes lignin, which would otherwise make the paper prone to acid hydrolysis. Almost pure cellulose is obtained. Glazer (2004) provides a detailed account of how the paper for the British colonial stamps was reportedly made.

During the coconut definitive era, De La Rue used machine-made wove paper from Wiggins, Teape & Co., made at Stowford Paper Mill near the southwestern tip of England (Glazer 2004, Yendall 2008). At least during the George V period, the paper was thought to have been plate-glazed between rollers to smoothen the surface before it was delivered to De La Rue (Fernbank 2013).

A bast (phloem) fibre extracted from a coconut definitive, under a 100× violet-corrected plan-apochromatic oil-immersion objective with Nomarski interference contrast. The fibre has longitudinal defects and characteristic lateral nodes at irregular intervals. Bast fibres come from annual crops grown widely in the tropical to temperate regions (Ansell & Mwaikambo 2009, Jones et al. 2017). The fibres contain more cellulose than wood fibres, and the cellulose tends to be more crystalline (Jones et al. 2017). Crystalline cellulose has highly oriented microfibrils and is birefringent (Donaldson 2009), meaning that its refractive index varies with direction. This causes optical interference which produces the Newtonian interference colours in the Nomarski image. Common types of bast fibres are hemp from the old ropes and sails of ships, and flax from linen rags (Dagnall 2009). The fibres in the stamp paper are more likely flax than hemp, as the latter is brown and cannot be bleached (Dagnall 2009). The predominance of linen fibres seems to contradict the report (Glazer 2004) that cotton rag was the main constituent of colonial stamp papers. It is not inconceivable that the source of rags varied between linen and cotton depending on availability. I tested only five stamps (Lin in press).

A softwood ray tracheid (water-conducting vessel) with bordered pits for fluid transfer between neighbouring cells. This is probably from Norway spruce. The plant has strong and flexible fibres that are particularly suitable for printing and writing (Tullis Russell 1950).

A probable softwood fibre extracted from a coconut definitive. It appears flat with some twisting as it has collapsed from its original cylindrical shape. Softwood pulp made the paper more dense (Glazer 2004).

Hardwood xylem vessel element from Scandinavian birch (Betula sp.), with characteristic fine oblique pitting (see Parham & Gray 1982, Safdari et al. 2011). Eucalyptus xylem has a similar pattern (see Foelkel 2007) but was not used at the time. This birch vessel was probably a contaminant; only a single instance was observed among fibres extracted from several coconut definitives and hardwoods were not in widespread use then (Robert Hisey pers. comm.). Nomarski interference contrast under 100× violet-corrected plan-apochromatic oil-immersion objective.

The coconut definitives started out on a so-called chalky paper. Glazer (1997) documents in detail the manufacture and application of the chalk coating, which was outsourced to Samuel Jones & Co. of London. Calcium carbonate was doped with varying proportions of substances like kaolin, aluminium oxide, calcium chloride and calcium sulphate to get the desired consistency. Salts of the natural milk protein casein were added to chemically encapsulate the chalk mixture. Solvent was then added to make a slurry that was applied to the paper. Finally the paper was heated to evaporate the solvent and finished by passing it between rollers.

The right side of this composite image shows the blue fluorescence of chalky paper under 365 nm longwave ultraviolet radiation.

The chalk coating yielded a crisp print and vivid colours, as it prevented ink from spreading through the fibre network (Melville 1916, Glazer 1997). It also supposedly made the stamps less prone to reuse (Easton 1949, Watterson 2004). When soaked in water, the casein salts were supposed to dissolve, thereby releasing the chalk and ruining the stamp. Glazer (2004), however, quoted the Crown Agents' former Chief Inspector of Colonial Stamps, Marcus Fauz, as saying that the paper coatings were meant to enable the use of certain inks and had nothing to do with fraud prevention. In addition, Fernbank (2013) mentioned that the coating was made “waterproof” using formaldehyde. Glazer (2004) also found that the chalk coating was often unencapsulated, making it waterproof and resistant to all but a very few dangerously corrosive reagents such as concentrated nitric acid.

The coating is distinctively pitted, perhaps due to heating, agitation or gas-producing chemical reactions. Blue pigment was mixed into the coating of this example, with contamination by green and even yellow pigment from the production of other coloured papers.

The surface and pitting of this chalky coating appear worn down. It is not clear whether it was made like this or was eroded over time.

One could mistake this for a satellite pass over the fractured karst landscape of the Yucatán Peninsula, with its ancient and mysterious sinkholes concealed in lush forest. The main image is one of 23 optical sections of a confocal laser scan of the chalky surface of the upper-left fascia pattern of a coconut definitive. The 3.60 μm-thick section was visualized by combining the fluorescence signals from simultaneous laser excitation wavelengths of 404.8 nm (1.7 mW), 486.2 nm (0.9 mW), 561.5 nm (0.9 mW) and 638.8 nm (1.6 mW). Laser power was measured at the tip of the optical fibre and totalled 5.1 mW before passing through the objective on its way to the stamp. The dwell time was 3.03 μs and there was no visible damage to the stamp. The fluorescence signals were amplified through gallium-arsenide-phosphide photomultiplier vacuum tubes. The chalky surface is both pitted and cracked. The deep orange spots in the image are particles of unknown composition fluorescing at approximately 595 nm. These are not discernible under normal illumination. The bars at the bottom and right side of the figure show the full z-profiles of the fluorescence along the x and y crosshairs. The profiles reveal that the letterpress printing has compressed the paper in the inked areas. The resolution on the x-y plane is 0.78 μm, while the z-resolution is 10.26 μm.

Separated fibres of chalky paper under Nomarski interference contrast microscopy (Lin in press). Dark purple ink particles are visible. See how the fibres were extracted.

In 1941, as war raged in Europe and De La Rue was bombed, striated paper (Barker 1996) appeared. It is thin, about 85 μm compared with the 105 to 150 μm of chalky paper (author's measurements using a micrometer screw gauge). It has streaks running across the stamp, which may have been produced through a manufacturing process similar to that of laid paper. The coating is thin and appears to contain very little or no chalk. Although chalk was plentiful in the British Isles, it required casein salts as a binder (Glazer 1997). Milk however was strictly rationed during the war. Because of this the main constituents of paper coatings at the time were kaolin and aluminium oxide (Glazer 1997). Chalk would make a comeback in 1948 (Glazer 2004).


At high magnification under reflected light, striated paper presents a texture reminiscent of asbestos.


Fibres of striated paper under transmitted light.

Constructing a high-resolution digital elevation model of the surface of striated paper using a Keyence industrial microscope. The instrument looks more like an electron microscope than a light microscope.


Separated fibres of striated paper under Nomarski interference contrast microscopy.

"Rough paper" appeared around the same time as striated paper. It had a texture similar to the latter, but was thicker, lacked the striations and had no appreciable coating. It may have been made from the same pulp.


Separated fibres of rough paper under Nomarski interference contrast microscopy.

After the war a "substitute paper" (Barker 1996) emerged. Its coating is thinner than that of chalky paper (Lowe 1951) and does not look like the latter. I suspect the coating is mostly kaolin (Al2O3·2SiO2·2H2O), given that many colonial stamps printed during and shortly after the war were found with kaolin coatings (see Glazer 2004). Kaolin, like chalk, is plentiful in Britain. It makes the paper more opaque and absorb ink more evenly (Glazer 2004). The only thing that will dissolve kaolin is concentrated hydrofluoric acid, an extremely dangerous chemical (Glazer 2004). These stamps were built for the most extreme conditions.

Substitute paper (as distinct from kaolin-coated papers) is apparently not common, reportedly having been used only for certain issues for Ceylon, Hong Kong and Malaya (Lowe 1951). Printings often have a crumpled-cellophane quality, with the ink forming puddles and accumulating along the edges. Pitting may occur, as in this case, but it is usually less pronounced than on chalky paper.


Separated fibres of substitute paper under Nomarski interference contrast microscopy.

Additional paper types have been used for the coconut definitive but rarely noted as such. One of them is the uncoated buff-coloured thin card impregnated with slender brown fibres, used in postal stationery bearing direct prints of the stamp.

The coconut definitive has also been printed on the even rougher aerogramme paper. See Singapore 25 cents for more images and discussion.

Yet more kinds of paper were involved in the genesis of the coconut definitive. First there was the plate-glazed paper or "glazed card" used for die proofs. The paper, though uncoated, was given a smooth ceramic-like surface by pressing it with heated metal plates. Ink texture on a specimen examined by the author (lot 586, Spink auction in Singapore, 28 October 2017) resembles that on substitute paper, with mottling and outlined edges, but gave crisp detail nevertheless.

In early 1941, De La Rue experimented with what they called "uncoated paper", making some test prints apparently using individual cliches. They might have been testing cheaper paper for wartime use. The rough surface yielded terrible print quality. The duty plate of the 1 cent appears to carry the plate flaw of the dot between the "T" and "R" of "STRAITS". The author examined these samples in the Crown Agents, Philatelic and Security Printing Archive at the British Library.

This so-called "plate proof", "printer's trial" or "printer's waste" on unwatermarked rough paper (Parr 1972, Stanway 2009), here showing Sultan Ismail of Trengganu, is similar in texture and colour to the buff-coloured card of postal stationery. This rare transitional stage between the die proofs and the production stamps was not officially recorded and may have served to clean the plate or remove excess ink; one occasionally finds the stamp of a different country on the same sheet (McClaren 2006)! This piece has two unevenly inked blocks and faint overlapping impressions of additional blocks that suggest plate cleaning. This specimen is unusual as most plate proofs of the coconut definitives are devoid of additional plate-cleaning impressions. These trials were supposed to be destroyed but a few made it out of the 'gulag'. Veteran philatelist Len Stanway noted that nothing was supposed to get out of security printing works, not even off-cuts from sheet edges after guillotining (Lin 2018d).

Plate proofs also exist in a rarer greenish grey paper of apparently similar fibre structure, here seen carrying the plates of Johore. Formerly in the collection of Dr Abdul Majid Dato Kassim. See Lin (2018a) for further discussion of circumstances surrounding plate proofs. Mudie (2018) reported similar imperforate test prints apparently made on actual stamp paper further down the production line.

Lin (2018d) proposed a possible source of the paper used for the plate proofs: could it simply have been the wrapping paper for the actual stamp paper? It would be big enough to take an impression of the entire plate. Why else would such a large piece of scrap paper be lying around? Stanway, however, argued that the paper used for test prints had to be of a consistent thickness and surface texture so as to expose plate anomalies, and that wrapping paper would not have been up to the task (Lin 2018d). The literature offers descriptions of the paper but stops short of hypotheses for its origin. Exploration in this direction could bring fascinating insights into the day-to-day goings-on in the printing room.

Acknowledgements
I am grateful to Robert Hisey, John Barwis, Rein Bakhuizen van den Brink, David Beech, Paul Skinner, Benedict Sim, Ernest Cheah, Clement Khaw and Goh Wah Ing for discussions and technical assistance, and to the Nikon Imaging Centre at the Singapore Bioimaging Consortium for providing state-of-the-art microscopy facilities.

References


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