But Is It Really Flax?


The archaeological study of the fibers and textiles used by a culture, and especially the processing and treatment of those fibers and textiles, has become an important consideration within the larger cultural contexts: the agriculture of the region, the trading routes of the merchants, their partners and destinations, and their technologies. It also provides clues about the gender roles within the society, reflecting the social and socio-economic relations of the population and the power networks within the social order.

Flax Stem diagram, with labeled sections
Figure 1: Flax Stem, with labeled sections

Textiles are a core part of life, and the knotting and intertwining of fibers to produce textiles is one of the oldest activities in human history. Bast fibers — the plant fibers woven into linen and found in the stems of certain plants — were the first fibers used, with the earliest sources being the inner bark of trees. (Rast-Eicher, 2016). 

Bast fibers are found between the outer layer of the stem (the skin) and the core of the plants. They were first harvested in wide strips from tree trunks and larger branches in the Neolithic Age, when the strips were used for weaving clothing and head coverings. Working with tree bast for so long let humans perfect their skills at processing bast fibers, so with the beginning of settlements, when agriculture brought about the domestication of flax and other bast plants (e.g. hemp, nettle, jute, ramie), those skills were easily transferred to the new source plants (Leuzinger & Rast-Eicher, 2011, 535).

With the establishment of settlements and the introduction of farming around 7000 BCE (Bar-Yosef, 2020), flax was first cultivated for the oil inside its seeds, which was initially used for cooking. Later the plant stems were also used for their fiber (Allaby, et al., 2005). While sheep may have been domesticated by the 4th millennium BCE (Rast-Eicher, 2005), they did not have a woolly coat at that point. Instead, their coat had two kinds of hairs: an outer coat of long, coarse hairs, and an undercoat of finer hairs. Both coats were shed each spring. Their domestication, along with a genetic mutation for continuous growth of the fleece, brought plucking or combing of this coat to gather these fibers, ultimately stimulating more undercoat production and finer hair. Animal fibers finally dominated plant fibers once these traits were established by the 2nd millennium BCE (Breniquet, 2010) (Shamir, 2015).


Because of the challenges of preservation, textile finds have always been much less common than other archaeological material. As such, even with the evidence of pollen from flax or hemp plants, the textile finds were often examined only through a standard light microscope, without any further testing to identify them more specifically – everything was automatically assigned as “flax”, since it was the fiber most well known by archaeologists not specializing in fiber and textiles.

The research history of brocaded tablet weaving reflects this, as well. There are many beautiful tabletwoven brocade patterns preserved solely through the metallic threads laying folded in situ in the shape of the brocade pattern. The metallic brocade weft threads have survived, while the warp threads underneath them – of less importance in the original bands, as they merely served as support threads for the ornate, metal threads of the brocade pattern – disintegrated over the centuries, unable to survive in the burial conditions of the various graves where they were unearthed because they were “flax” threads (i.e. bast threads). Without actual surviving samples of these threads now, there is no way to identify them as either flax, nettle or hemp. They were arbitrarily assigned to “flax” when they were first examined.

In 2010, Bergfjord, et al., issued a comment in Science on this identification, arguing that the features pointed out in the supporting online material were not conclusive for flax, but instead could be found in several different types of bast fibers. Beyond this, other techniques would be required to identify the specific fibers that were found. 

In their response to this critique, Kvavadza, et al., (2010) disagreed with these conclusions as presented, and described (in detail) their experimental procedures for identifying the fibers as flax. Their procedures, they argued, follow the best practices of current bast fiber research, examining both the external and internal structures of the fibers with light microscopes, which “has revealed time and again the essential characteristic traits of fiber morphology and allowed plant identification.” (Kvavadza, et al., 2010, final paragraph).

The stream of articles this original discussion created shifted the research trajectory for bast fibers within the field of archaeological textiles into a whole new direction. No longer could researchers look at a fiber, recognize it as a bast fiber, and immediately say, “Oh, that must be flax!” There is still controversy on the identity of the 30,000-year-old bast fibers that began this discussion (they might even have been tree-bast fibers, from a linden, willow, or oak tree in the region), and on many of the fibers that have yet to be examined by the procedures that researchers use now.

Identifying Fibers

Being able to distinguish between different fibers in textiles is an important point of concern in textile archaeology (Bergfjord & Holst, 2010) (Haugan & Holst, 2014). Animal fibers (e.g., wool, angora, mohair), silk and cotton fibers are all easily identified, especially when examined under a microscope.

Bast fibers, however, have always been difficult. Bergfjord & Holst (2010) reviewed the many previous methods used to try to sort out the bast fibers from each other, and showed why each procedure was inconclusive: the surface features (nodes and striations along stems) between flax, nettle, and hemp are very similar (see Figures 2-4), the cross-section size and shape of fibers are insufficient for any positive identification due to wide size variation within each species (see Figures 5-7), and the differing stem shapes only separate the fiber types into two different clusters: flax or nettle/ramie, as opposed to hemp or jute.

Figure 2: Z and S twist in fiber
Figure 2: Z and S twist in fiber

There are other laboratory methods that could identify the fibers, but those methods require specialized equipment and larger samples of the archaeological fibers (always in short supply, and destroyed by most testing) that make it prohibitive in all but a few situations. DNA analysis could also identify each species, but living cells with nuclei are required, something archaeological specimens lack.

The procedure Bergfjord, et al. (2010, p. 1193) presented for identifying different bast fibers used a combination of examining the fibers with polarizing filters on a light microscope to measure the twist direction (Z or S) of individual fibers in stem cells, and to detect the possible shape of a particular crystal type (calcium oxalate) found in the stem of bast plants. Using these identifying features, the authors are able to sort the fibers into four different groups: flax, nettle/ramie, hemp, or jute.

Figure 3: Calcium Oxalate crystals in normal and polarized light

This test for identifying fiber, called the modified Herzog test (or red plate test) (Herzog, 1955, cited in Haugan & Holst, 2013), became the accepted procedure, and gained a reputation for never producing false results, but also for occasionally not being able to produce any results or conclusions at all. In their 2013 publication, Espen Haugan and Bodil Holst supplied a justification for this result by showing that the test relied on the thickness of the three secondary cell walls within the fibers. 

Figure 4: Diagram of a typical textile bast fiber cell, showing the fibrillar orientations the sublayers. Cell sublayer S2 is shown with the Z-twist.
Figure 4: Diagram of a typical textile bast fiber cell, showing the fibrillar orientations the sublayers. Cell sublayer S2 is shown with the Z-twist.

Each sublayer of the wall of the fiber cell could act as a polarizer of the light being shined through the cell (changing of the color of the light passing through the fiber as the fiber is turned on the microscope stage) once as the light entered the cell, and again on the other side of the cell as the light exited the cell. Whichever wall was the thickest would become the dominant polarizer, and the other two sublayers could be ignored. The second part of the analysis sorts out, through color changes from turning the fiber on the microscope stage, which angle of the light is caused by the front wall, and which by the back wall – this decides if the fibers are Z-twist (as in Figure 5) and which are S-twist. 

If none of the three secondary walls of the fiber cell layers is significantly thicker than the other two, the expected color change of the fiber (caused by the polarization of the light passing through the fiber walls) doesn’t occur.which angle of the light is caused by the front wall, and which by the back wall – this decides if the fibers are Z-twist (as in Figure 5) and which are S-twist. 

Haugan and Holst (2014) continued the assessment of the Herzog test’s viability to identify the fibers of archaeological textiles using features that had been considered definitive to earlier researchers   diameters of the fiber cross-section and the lumen (the central empty space of the fiber), the dislocations (nodes) and cross markings along the length of the fibers, and the shapes of the fiber lumen and cross-section –- to see if those features actually do identify the fiber types reliably. They photographed modern flax, nettle and hemp fibers with a wide variety of microscopes — standard, transmission, white light, compound and polarizing: equipment commonly found in laboratories

Figure 5: Note how the front and back of the cell wall have their fibers tilted at the same angle, but at opposite orientations.
Figure 5: Note how the front and back of the cell wall have their fibers tilted at the same angle, but at opposite orientations.

dealing with fiber identification. The results of their review of the traits (2014, 954-959) found examples of each fiber (flax, nettle and hemp) that had traits noted as being a unique characteristic for another fiber type. They concluded that the traits “cannot be taken as unique identification criteria.” (p.957). This bolstered the argument for using more than just a standard or polarized light microscopic examination when identifying archaeological fibers and textiles. (As the title of their article indicates, there are, indeed, pitfalls to ancient plant fibre identification.)

The nodes (at the arrows) and striations (lines along the surface of the cell) of flax, nettle and hemp

Figure 6: Flax surface features
Figure 6: Flax surface features
Figure 7: Nettle surface features
Figure 7: Nettle surface features
Figure 8: Hemp surface features
Figure 8: Hemp surface features
Figure 9: Flax cross section
Figure 9: Flax cross section
Figure 10: Nettle cross section
Figure 10: Nettle cross section
Figure 11: Hemp cross section
Figure 11: Hemp cross section

The cross sections of flax (polygonal, small lumen), nettle (oval) and hemp (polygonal, flat lumen)

Lukešová & Holst (2021) followed up on this research by examining the cross-section and lumen shapes of retted and unretted fibres in the stem of modern flax, nettle, and hemp plants. They found that these two criteria are still inconclusive for identification, as non-characteristic shapes could be found in each of the species. Their conclusions also emphasized that, while their study used modern material in a quantity likely to give a statistically-sound sample, when the process is shifted to archaeological material — where nothing can be known about the growth conditions of the fibers, and the samples available for study are not likely to be statistically significant — “Proper identification is only possible by the combination of several methods, … and even then, secure identification cannot always be ensured. Precise knowledge of material use in cultural heritage collections is important for understanding resource management in the past. Hence, it is important to keep searching for new ways to identify plant fibre species in historical objects” (Lukešová & Holst, 2021, p.224).

Applying the New Procedures

In 2012, Christian Bergfjord, et al., used the new plant fiber identification method described in their 2010 article to test the Lusehøj textile, a 2800-year-old textile from one of the richest Bronze Age graves discovered in Denmark. Using blind testing, including modern textiles of known origin, they were able to identify the fiber as being nettle, due to the S-twist of its fibers and the identification of the calcium oxalate crystals within the fibers. (At the same time, they also tested the strontium isotope characteristics and discovered that the nettle was not locally grown – a surprise to them, since nettles are not grown agriculturally. The nettles had been harvested in Central Europe, and the fiber imported to Denmark.)

In her 2017 paper, Hana Lukešová discussed how well the combination of two techniques — microscopy and the modified Herzog test — worked when used to investigate Merovingian period and Viking Age plant fiber textiles from western Norway. She found the Herzog test gave reliable answers when the Slayer of the secondary cell wall was examined. (See Figure 4 for the primary and secondary cell wall layers.) She also pointed out that having the fibers in exact focus was important, and that degraded archaeological material didn’t respond reliably to the test. Ultimately, it was still necessary to further separate the fibers into S-twist and Z-twist groups for final identification.  When combined, Lukešová felt the tests were reliable for identifying different fibers in archaeological textiles.

G. Skoglund, Margareta Nockert and Bodil Holst, in their 2013 paper, examined 10 different Scandinavian plant fiber textiles from the Viking Age and early Middle Ages, previously thought to be locally produced and made of flax. Both flax and hemp seeds and pollen had been found in Scandinavian settlements during archaeological digs, with hemp finds often having been quite plentiful and earlier than those of flax. There was also extensive evidence found of processing fibers of each type in various Scandinavian settlements of the period. Generally, even though hemp fibers might be almost as fine as flax fibers, it was believed that hemp was used for coarse textiles, such as ropes and sailcloth, while flax was used for clothing and household textiles. As Skoglund et al. pointed out, this was “reflected in the fact that throughout the literature, including but not restricted to the literature on Scandinavian Viking and Early Middle Ages, most fine plant fibre textile remains are referred to as flax without any mentioning of analytical tests.” (2013, p. 1-2)

The textiles being examined by Skoglund, Nockert and Holst (2013) were all made from plant fibers combined with wool, and were carbon-dated between 7801420 AD. These were church textiles thought to have been locally produced, based on the patterns and textile techniques used. The modified Herzog test was used on fibers extracted from the textiles, and the results showed, surprisingly, that 4 of the 10 textiles contained hemp fibers, while 3 others had mixtures of hemp and flax. They also noted that other textiles might have had mixed fibers which were not located due to the selections for thread extraction made by the curators of the museums housing the various textiles, and that different fibers might have been used for the warp and weft of the weavings. Another variable not tested was whether the fibers were locally grown, rather than imported. Given results found elsewhere, this could be an important question — a strontium isotope analysis could provide an answer in the future.

Skoglund, et al., advocate for a future detailed analysis of the distribution of hemp and flax usage in Scandinavia. As they point out, “The big question, from a cultural history and historical research management point of view is: Why use one material instead of another? When hemp and when flax?” Their conclusion was that it may be based simply on local growing conditions (2013, p. 2).


Significant evidence from recent research has demonstrated the value of using multiple testing methods for identifying the fiber content of any textile using bast fibers, and several other procedures (not discussed here) have been added to the potential choicesof tests for fiber identification. For now, this research has been restricted, for the most part, to Scandinavian-based textiles, possibly because of the strong research network that has developed in that region. This research needs to be continued: a review of all major finds of “flax” fiber would help revise the history of flax and hemp introduction in Scandinavia, the two major bast fiber crops grown by farming, in the area. Since nettle is only harvested from “wild” plants – it can’t be grown “agriculturally” – this review should seriously revise the history of bast plants throughout Europe, impacting the socio-economic profile of the region. And, eventually, maybe we will finally know if the 30,000-year-old fibers that started this discussion actually are flax, or if they are a tree bast fiber that was found in that region during that period.

If we (within our Society) want to bring our skills for experimental archaeology into the academic community and add to this exploration of bast fibers and their use, we should start experimenting with a greater variety of bast fibers for spinning, weaving, and in our recreations of period fabrics. With our hands-on skills, we may be able to demonstrate which bast fibers are easier to process and to weave into fine (and coarse) cloth – an area of research that has yet to be seriously explored within academia.


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