Without paper, there would be no postage stamps. A stamp design combines crucial postal information with artistic creativity in an appealing package, but it is the paper that displays the design, carries it far and wide for the world to enjoy and even preserves it for posterity.

Since its invention in about 200 B.C., the raw materials, manufacturing methods and additives of paper have diversified to give it desired properties for myriad uses. Yet the philatelist hardly ever has to worry about the details of the paper. Although many different types of paper have been used to print stamps, any given issue is usually printed on the same type of paper, so there are no varieties to examine or document, for instance in the way of shade varieties.

Figure 1. The Malaya Universal Coconut Duty Plate shown with the bust of King George V (Straits Settlements Stanley Gibbons 270).

Figure 2. The four main paper varieties of the coconut definitives: From left, striated (Japanese occupation of Malaya SG J148b), rough (Malaya British Military Administration SG 11), chalky (Straits Settlements SG 269) and substitute (Malaya British Military Administration SG 16) paper.

But if a stamp is issued through a time of economic and political upheaval, paper varieties may arise. One interesting case study is the Universal Coconut Duty Plate of Malaya¹ (Figure 1, henceforth referred to as coconut definitives). This iconic design by De La Rue debuted in 1936 with the bust of King George V and continued through King George VI to Queen Elizabeth II, spanning the almost three decades before, during and after World War II. It also carried the heads of nine different sultans who ruled the individual Malay states. The endless permutations of design variations, papers, shades, overprints and even errors and forgeries make the coconut definitives highly collectible. For paper, the subject of this article, at least four distinct varieties are known to have been used (Figure 2), with differences in thickness, coating substances and texture. Their characteristics overlap and have caused confusion and misidentification.

On the level of the cellulose fibers, these paper varieties are very similar. At the time of the coconut definitives, British colonial stamp papers were 80 percent rag (linen or cotton), which made the paper strong, with the rest of the pulp made up of softwood.² Many other plant species have been used throughout postal history, including bamboo and silk (an animal protein).

Figure 3. Flax fiber under the polarizing microscope (left); water-conducting vessel from a softwood, probably Norway spruce (right).

In the coconut definitives, the rag component is mainly flax (Figure 3) which is distinguished by the irregular nodes and scaly texture of the fiber. Flax also has different optical properties in different directions, which generate interference colors when studied under a polarizing microscope as shown; these colors can be measured quantitatively to identify the fibers. For such work the fibers have to be extracted in a destructive process; John Barwis’ 2013 treatise “Paper characteristics of U.S. 3¢ stamps, 1870–1881” and the author’s article “Microscopic structure of stamp paper surfaces and fibers” go into more detail about this process.

The softwood component of the paper is most likely Norway spruce, which can be identified by its water-conducting vessels with distinctive ring-shaped structures (Figure 3). Softwood fibers are generally longer and more flexible than hardwood and make the paper denser.³ The softwood pulp was treated with sulphite to remove lignin in the plant cells, which was acidic and would turn the paper yellow with time.

In the coconut definitives, fiber composition is where the similarities end. Various differences in manufacturing processes produced papers with different appearances and/or print characteristics.

One identifying feature that you may note on the stamps in your collection is a raised or depressed pattern on the paper surface. The most familiar examples are laid paper and watermarks, where the patterns were made by wires when the freshly formed sheet was being dried. Laid paper was traditionally made by draining water from the pulp through a wire sieve, which impressed the pattern⁴, while watermarks were often pressed onto the sheet with a dandy roll carrying the desired wire pattern. But sometimes, there are patterns not made by wires.

Figure 4. Striated paper (1941, Straits Settlements SG 294) with distinctive crinkling made more visible by the ink.

In the coconut definitives, a wartime paper known as striated paper⁵ has fine horizontal crinkles that are too irregular to have been made by wires (Figure 4). This paper is particularly thin, with an average thickness of about 85 micrometers as measured with a micrometer screw gauge, compared with the 100 μm or greater thickness of the other papers.

It was previously thought that the paper might have crinkled along the grain of the fibers when it was wetted during coating or gumming (Norris 2019).⁶ This would have happened as the paper expanded across the grain rather than along it. Grain is produced during papermaking when the majority of the fibers get aligned in the direction of machine movement. However, the author, in collaboration with Robert Hisey, determined in 2020 that the crinkling was perpendicular to the grain, so this theory became untenable.

From the author’s research with Hisey, the current explanation is that the process of crinkle formation began as cockling, or wrinkling, of the thin paper as it was being dried. This cockling was non-directional because it was caused by random variations in fiber distribution and moisture content.

Subsequent application of coating or gum might have amplified the cockling, as the slurry or gum would each have been applied on one side of the paper. By wetting only one side a moisture gradient is generated, which encourages cockling.⁷ At this stage the cockling was still non-directional.

It was only when the paper was calendered, or passed between rollers to flatten it, that the cockles were squashed into the elongated crinkles seen on the final product.

Figure 5. Close-ups of striated paper (left, Straits Settlements SG294) and rough paper (right, Straits Settlements SG 295).

Further insights can be gained from a similar paper that appeared in the coconut definitives at around the same time as striated paper but was not crinkled. This so-called rough paper (Figure 5) is thicker and has no appreciable coating, while striated paper has a very thin coating. The thickness of rough paper made it less prone to cockling, and the lack of a coating meant the paper did not experience an additional wetting step that would introduce or amplify cockling.

Figure 6. Note the patterns left by papermaking mesh of different weaves (as shown by red guide lines): at left, a plain weave with symmetric diamond hatch pattern; center, a plain weave with more equal spacing of horizontal and vertical threads; at right, a twill weave with diagonals that are asymmetric in both angle and spacing.

There is yet another cause of raised patterns on stamp paper that is not generally recognized: the fine woven mesh used for making wove paper, which is considerably finer than the wires used for making laid paper. The pattern is quite faint if present at all, and can be seen only on the back of the stamp where there is no coating and the gum has been removed (Figure 6). It is best to use oblique lighting of moderate brightness and move both the light and the eye around to find the optimal contrast.

There are different ways of weaving the papermaking mesh, such as the plain and twill weaves from the textile industry, and different mesh sizes. At least three varieties of weave pattern occur in the coconut definitives as seen in Figure 6. These were first reported by Rein Bakhuizen van den Brink on the Stampboards online forum in 2020 and subsequently studied in more detail in collaboration with the author.

All that has been discussed so far, however, is just half the story. The other half is the paper’s coating, which is often thick enough to completely cover the fibers below and helps improve characteristics like print quality and paper brightness.

The two main coating substances found on the coconut definitives are chalk (calcium carbonate) and kaolin (aluminum silicate), as revealed by energy-dispersive X-ray spectroscopy and reported in the author’s 2020 article. 

The chalk is predominant on the well-known chalky paper, while kaolin is predominant on what philatelists and catalogs variously call ordinary, or substitute, paper. Substitute paper appeared right after the war and was reportedly⁸ used only for a few issues for Ceylon, Hong Kong and Malaya. For British colonial stamp papers more generally, a few other calcium and aluminum compounds were also added to the coating slurry in varying proportions to get the desired consistency.⁹

Two methods have commonly been used to distinguish chalky paper from substitute paper and other varieties, one method being the silver test¹⁰, which relies on the abrasiveness of chalk. This has turned out to be unreliable for two reasons. Firstly, whether the silver leaves a gray mark partly depends on the proportion of silver in the testing implement. Silver solder containing a relatively high proportion of 55 percent silver may leave a mark where a silver coin does not. Secondly, striated paper has calcium carbonate in its coating and gives a positive silver test. It will be misidentified as chalky paper based solely on the silver test.

Figure 7. Close-ups of chalky paper (left, Straits Settlements SG 266), substitute paper (center, Malaya British Military Administration SG 18) and a densely pitted form of substitute paper (right, Malaya British Military Administration SG 14).

The other common method for distinguishing chalky paper is to look for small pits in the coating (Figure 7, left) using a jeweler’s loupe. But it is unreliable as there are many cases of substitute paper with pitted kaolin coatings (Figure 7, right) and chalky paper with little or no pitting. The pits were probably left by bubbles formed during heating or mechanical mixing of the coating slurry and are not unique to chalky coatings. Measurements from photomicrographs indicate that substitute paper tends to have slightly smaller pits on average, but this is far from a reliable differentiator.

A more reliable means of identification is the appearance of the print, which is influenced by the texture of the coating.

Chalky paper was coated with coarse natural rock chalk rather than fine precipitated chalk, which gives it a microscopic porosity that lets the ink soak evenly into the surface (Figure 7, left).

In contrast, the clay-like kaolin coating on substitute paper is much smoother microscopically, causing the ink to puddle on the surface and creating patchy color intensity (Figure 7, center and right). In both cases the coatings prevented ink from spreading through the underlying fiber network,¹¹ yielding crisper prints than on the virtually uncoated rough paper. A 10× loupe is sufficient for seeing these differences, or even the naked eye if one has good eyesight and knows what to look for.

Another interesting aspect of chalky paper is its supposed security purpose of making the stamps less prone to reuse.¹²

When chalky paper is soaked in water, casein salts that were used to encapsulate¹³ the chalk grains are supposed to dissolve, thereby releasing the chalk and ruining the stamp. In a 2004 article, Myles Glazer, however, quoted the Crown Agents' former Chief Inspector of Colonial Stamps, Marcus Fauz, as saying that the coatings were meant to enable the use of certain inks and had nothing to do with security. In addition, Peter Fernbank in 2013 mentioned that the coating was made “waterproof” with formaldehyde. Glazer also found that the chalk was often unencapsulated, making it waterproof and resistant to all but a few dangerously corrosive reagents such as concentrated nitric acid.

Analysis of the paper varieties of the coconut definitives has resulted in more accurate paper identification and revealed the mechanisms underlying interesting characteristics such as the crinkling in striated paper. Some of these paper quirks are unlisted and may not be necessary for matching stamps to catalog listings, but they add another dimension to specialized collecting.

More generally, a better understanding of the physical and chemical properties of stamp papers yields fascinating insights into stamp issues and postal history, and could also help with forgery detection. Furthermore, it could make philately more multidisciplinary and attract more people to the hobby to perpetuate humanity’s heritage of miniature art.

Acknowledgments

I am grateful to Robert Hisey, the late Rein Bakhuizen van den Brink, Benedict Sim, Ernest Cheah, Clement Khaw, Li Zhen and Wulf Hofbauer for their insights and technical assistance. I also thank the Nikon Imaging Center in Singapore and the Science Center Singapore for the use of research facilities.

References

Barker, William H. “Trengganu: the printings of the postage stamps, 1921–1941,” The Malayan Philatelist 37 (1996): 25–35.
Barwis, John H.”Paper characteristics of U.S. 3¢ stamps, 1870–1881,” In Proceedings of the First International Symposium on Analytical Methods in Philately, edited by Lera, T., Barwis, J. H. & Herendeen, D. L. (Washington, D.C.: Smithsonian Institution Scholarly Press, 2013): 5-18.
Easton, John. Postage Stamps in the Making. (London: Faber & Faber, 1949).
Faux, Marcus. “Stamp production at the Crown Agents,” The London Philatelist 95 (1986):109–111.
Fernbank, Peter. King George V Key Plates of the Imperium Postage and Revenue Design (Alicante: British West Indies Study Circle, 2013).
Glazer, Myles D. “WWII paper coatings on some King George VI large Nyasa-type stamps,” GEOSIX 181 (1997): 3-10.
Glazer, Myles D. “The papers used to print the King George VI colonial stamps,” GEOSIX 213 (2004): 1-10.
Lin, Yangchen. “Microscopic structure of stamp paper surfaces and fibers,” In Proceedings of the Fourth International Symposium on Analytical Methods in Philately, edited by Lera, T. & Barwis, J. H. (2020): 37–45.
Lin, Yangchen and Robert Hisey. “A theory of striated paper formation,” The Malayan Philatelist 61 (2020): 33–35.
Lipponen, Pasi, Teemu Leppänen, Jarmo Kouko and Jari Hämäläinen. “Elasto-plastic approach for paper cockling phenomenon: on the importance of moisture gradient,” International Journal of Solids and Structures 45 (2008): 3596-3609.
Lowe, Robson. The Encyclopædia of British Empire Postage Stamps Volume III: the Empire in Asia (London: Robson Lowe, 1951).
Melville, Frederick J. Postage Stamps in the Making (London: Stanley Gibbons, 1916)..
Norris, Andrew. “Striated paper,” The Malayan Philatelist 60 (2019): 64–65.
Watterson, Neville. “De La Rue and their use of chalky surfaced and coated papers,” The Malayan Philatelist 45 (2004): 88–89.

Endnotes

1.   See https://www.linyangchen.com/Philately for more information on the coconut definitives. For reference, most catalogs do not note all of the varieties nor give extensive descriptions. The best references can be found in articles, named in the reference section.
2. See Faux’s 1986 article “Stamp production at the Crown Agents” and Myles Glazer’s 2004 “The papers used to print the King George VI colonial stamps.”
3. As found by Myles Glazer in “The papers used to print the King George VI colonial stamps,” published in 2004.
4. This was the traditional method - there are modern versions of “laid” paper made by machine to emulate the same look.
5. Striated paper can be found on British colonies stamps. A global survey of stamp papers might expose other examples of paper with similar features resulting from a similar manufacturing process (or even different processes that gave a similar result). For more information about “striated paper” see William Barker’s article “Trengganu: the printings of the postage stamps, 1921–1941.”
6. This possibility was contemplated by Andrew Norris in his 2019 article “Striated paper.”
7. As found by Pasi Lipponen (et al) in their 2008 article “Elasto-plastic approach for paper cockling phenomenon: on the importance of moisture gradient.”
8. According to Robson Lowe’s 1951 encyclopedia.
9. As found by Myles Glazer in his 2004 article “The papers used to print the King George VI colonial stamps.”
10. The silver test is done by dragging the edge of a piece of silver-containing alloy, such as a silver coin, across the surface of the stamp. This will make a gray or black mark on chalky paper as the chalk is abrasive and scrapes off some silver. The author does not recommend this test for obtaining conclusive results. Effects of silver solder versus coins and the results of the silver test on striated paper were shared with the author by Robert Hisey.
11. See Melville (1916) and Myles Glazer’s 1997 article “WWII paper coatings on some King George VI large Nyasa-type stamps.”
12. See Easton 1949 and Watterson 2004.
13. Encapsulation is a process in which molecules of a reactive substance are made inert by surrounding them with another substance. If required, the former can be reactivated by releasing it from the latter by physical or chemical means.