Bissye — Sea Silk and Byssus Fibre | bissye.com
The two fibres share a word: one comes from a pen-shell beard at 10 to 50 microns, the other from the flax plant and was what Egypt wrapped mummies with.
Start with the source. Genuine sea silk fibre was historically spun and woven into cloth from the beards of pen shells; linen comes from the flax plant. Beard against stem settles the question before any measurement is taken.
Then read the diameter. Byssus spans 10 to 50 microns, a wide animal-fibre range. Linen is a plant fibre and does not share that origin, so a sample whose provenance is a pen-shell beard is by definition not flax.
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The Egyptian case is the clearest illustration. In ancient Egyptian burial customs byssus was used to wrap mummies, but that was linen and not sea silk — the same word, a different material, and the reason the two are confused today.
The comparators help as well: silk at 11 to 15 microns, merino wool at 18 to 25 and mohair at 20 to 40 are all animal or insect fibres measured on the same scale as byssus, which is how the table above reads.
Practical test: ask where the fibre came from. A pen-shell beard gives byssus; a flax field gives linen, whatever the label says. The sea silk industry has almost disappeared, so byssus is difficult to come by and misnaming is easy to encounter.
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