Plant Cuttings

This image, of cranes made by origami of washi paper by Laitche, is in the public domain.

Whenever I hear the word ‘paper’, I usually think of the modern-day writing material that’s made from compressed pulp from trees. If I think for a little longer I recall Ancient papyri (Stephen Harris, Joshua Mark) made from the papyrus plant (Cyperus papyrus (Ian Popay)). But, that’s about it for me and plant-based papers (unless we count newspapers that used to be printed on paper manufactured from the fibres in repurposed cloth items made from plants such as cotton and linen (Sandy Ryan). Commonly known as rags, those materials may – or may not – give us the slang word ‘rag’ that is sometimes used to refer to newspapers)*. What I didn’t think of was ‘washi’.

Washi is a Japanese word that translates into English as Japanese paper (David McElhinney & Lucy Dayman). Because that is what it is, a type of handmade – that distinguishes it from Western machine-made paper – paper from Japan. Although developed in Japan over 1400 years ago (David McElhinney & Lucy Dayman), the paper-making process ultimately comes from a technique that originated in China. Washi manufacture has been recognised by UNESCO as part of the ‘intangible cultural heritage of humanity’, and was added to that list in 2014.

Washi is a broad term for a range of papers made from one or a mix of the fibres of several plants (David McElhinney & Lucy Dayman). Three of the most notable** are kozo (paper mulberry, Broussonetia papyrifera), mitsumata (oriental paperbush, Edgeworthia chrysantha), and gampi (Wikstroemia sikokiana). With many desirable qualities – e.g. strength, warmth, soft translucency, flexibility, absorbency, and lightness – washi seems to be the perfect paper product. But, apparently, not perfect enough.

So, Lovisa Rova et al. (2024) have made a new version of washi***. Incorporating polybutylene succinate (PBS) into traditional washi sheets has created a material that “was 60% stronger than the original washi and was also more biodegradable” (Mihail Andrei). PBS is a thermoplastic, semi-crystalline polymer with mechanical properties and processability comparable to other commonly-used plastics such as polypropylene and polyethylene, and one of its most notable properties is its good biodegradability in composting conditions (Rova et al., 2024).

The enhanced biodegradability of the ‘techno-washi’ is one of the characteristics that is seen as an important point in favour of the 21^st century version of washi. When biodegraded it can be used as a mulch film that enriches the soil after its decomposition, and in disposable furniture as a more sustainable alternative in an industry which has hitherto been reliant on materials that are not often recyclable (Mihail Andrei). However, as PBS is currently derived from fossil fuels, there are concerns regarding its ‘environmental credentials’ (Mihai Andrei). Maybe a sustainable source for PBS can be found in future****.

Interestingly, the new paper’s “increased strength was attributed to PBS working as a glue, filling the empty structure between the cellulose fibers of the washi” (Rova et al., 2024), which sounds like the role traditionally played by ‘fermented hibiscus root’. It was not clear to me from the scientific paper whether the washi ‘adulterated’ with PBS had been hibiscus-root-treated. If not, it would be insightful to compare the strength – and biodegradability – of ‘hibiscified’ washi to the PBS version. That would at least tell us how the 21^st century solution compared to the traditional, centuries-old innovation. If the hibiscus version was better, there is still the problem of sourcing sufficient fermented hibiscus root to compete with PBS. But at least it should be 100% sustainable as compared to present-day sources of PBS.

However, strength isn’t the only important characteristic of washi, there are many others which make it suitable for many different purposes. It would be good to know how PBS-washi fares for such uses as printing and writing, bookbinding, origami (Nick Robinson) and interior design (David McElhinney & Lucy Dayman). How well will the PBS version of washi wash with washi users? For now, one suspects that traditionalists may well shun this newfangled version, and prefer to patronise the artisans who still make washi ‘in the old way’. [And, Mr P Cuttings does wonder if washi made in this new hi-tech way may undermine the ‘intangible cultural heritage status’ of traditional washi. indeed, can it be called washi?]. On a more positive note, it might well be that traditional washi is still the material of choice for all of the traditional uses of washi, and the PBS version is a composite reserved for other purposes.

* Having done a bit of research for this item, I now know that paper is “an aqueous deposit of any vegetable fibre in sheet form”, which can be made from many plant sources – not just trees or those used to make washi, e.g. cotton, flax, esparto, straw, hemp, and jute, and bamboo, cork, and mulberry.

** Other plants may also be used, including bamboo [which is also used to make the screen used in the paper-production process], hemp, and rice, and abaca. And, for good measure, the fibres are bound together using mucilage derived from ‘fermented hibiscus root’. Compared to paper made in the West from wood pulp, multi-botanical washi is generally tougher.

*** For a most insightful scicomm article on this work, see Mihai Andrei.

**** Impetus to achieve this is likely to come from several sources, not least those with commercial interests in exploiting its biodegradable-plastic property (e.g. Laura Aliotta et al., 2022; Taylor Nelson et al., 2022; KS Savitha et al., 2022).

REFERENCES

[In an attempt to improve narrative flow, fuller citations for scientific articles have been removed from the text above to this new section [thank you, Chris!] – do let me know if this move helps readability.]

Laura Aliotta et al., Polymers 2022, 14(4), 844; https://doi.org/10.3390/polym14040844

Taylor Nelson et al., Nat Commun 13, 5691 (2022); https://doi.org/10.1038/s41467-022-33064-8

Lovisa Rova et al., Composites Part A: Applied Science and Manufacturing 184, September 2024, 108261; https://doi.org/10.1016/j.compositesa.2024.10826

KS Savitha et al., Polym. Chem. 13: 3562-3612, 2022; https://doi.org/10.1039/D2PY00204C