What do the Sizes of Linen Thread Actually Mean? It’s Complicated.

Some common sizes of linen thread for bookbinding, ranging from 18/6 to 80/3.

Bookbinders likely know that linen thread is classified by a two number system, such as 35/3. And most know that the second number represents the number of threads plied together, and the first number how thick or thin the thread is.  But what does the first number actually refer to?

It turns out that two different systems, an English system and a Metric system that use a similar two part description of size separated by a forward slash. However, these two systems are not the same. Most thread sold by bookbinding supply companies uses the English System.

The English system (aka. Number English, Lea, NeL, Linen Count) is based on how many skeins (of 300 yards) make up one pound in weight. I *think* this means that twelve  12/1 skeins would weigh one pound, or thirty-five 35/1 skeins would weigh one pound. I’m still not sure how adding the plied threads results in the classification. Would a 35/3 thread weigh 3 pounds?

The Metric system (Nm, aka. the Japanese Gunze Count) is based on how many meters of thread weigh one gram.  So I think for a 60/1 thread, 60 meters weighs one gram. It is the same as the English system in that overall, thicker and stronger threads have lower numbers.

Other thread systems include:

Tex — How many grams 1,000 meters of a thread weighs. In this case, the larger the number, the thicker the thread.

Denier — How many grams 9,000 meters of a various thread weights. Again, the larger the number, the thicker the thread. This is useful for very thin threads and microfibers.

Grist — Yards per pound.  For example, a 20/1 linen is 3,000 yards long per pound. Different fibers have different weights.

I’m still not sure what system the Londonderry Linen Lacing Thread in the image above uses. It is labeled only a mysterious “#4”. I love sewing with this thread, though, since it is thick, soft, easy to untwist, tangle free without waxing, and remarkably compressible. It is possible to sew a book naturally packed with it. It consists of five plies, and is roughly equivalent to a 20/5.

If you are wondering what size thread you should use to sew a book, check out my Guide to Swell.

Finally, Colophon Book Arts is a reasonably priced, one stop shop to purchase a wide variety of sewing threads.

Wait, there are more systems  … AARGH!      https://en.wikipedia.org/wiki/Units_of_textile_measurement



Cor Knops, of Knops Boekrestauratie in the Netherlands,  kindly sent me these images of some antique thread he owns.


Great name!

These packages contain hanks of thread, and all weight about a pound.  I think the package on the left is 25/3, and on the right 12/3. So if my calculations are correct, the 12/3 should contain 1200 yards of thread, assuming a 12/1 would contain 12 – 300 yard skeins = 3600 yards.  Enough thread for a lot of books in any case!

Vesalius, Sixteenth Century German Bookbinding Thread and Dissection Tools

Vesalius, De humani corporis fabrica libri septem, 1543, 235. Source: https://www.nlm.nih.gov/exhibition/historicalanatomies/Images/1200_pixels/Vesalius_Pg_235.jpg

While looking at the surgical tools in De Humani Corporis, I ran across an interesting bit of information from a Cambridge University Online Exhibition. The image is huge, and can be examined in detail. In the text, Vesalius mentions that either silk threads or bookbinder’s threads could be used to prepare a cadaver. In his opinion, German bookbinding thread is the best quality, since it is stronger, thinner, and more well-twisted than thread from other countries. I haven’t noticed this about German 16th C. sewing thread (in large part due to the inflexible spines, see the post below) but it is certainly true for their typically tightly cabled sewing supports. One takeaway is that the thread bookbinders used was the best quality available. Vesalius also describes heating a needle  in order to bend it into a “C” or parenthesis shape, a practice bookbinders still perform today. I’m assuming these bent needles, labeled “N” are stuck in bookbinding thread wrapped up in a bun shape.  This is likely the earliest image of bookbinding thread.

Anthropodermic bibliopegy, or the binding of books in human skin, has a lurid and enduring fascination. Here; however, we have the cadaver fabricated using a bookbinding material and borrowed or shared tools: Bibliodermic anthropegy???


More tools appear on the title page of this book, where a man is stropping or sharpening his razor under the dissection table. The portrait of Vesalius also contains a partially hidden razor lying on the table as he holds body parts of a cadaver. In this case, the razor represents his practical knowledge and experience. His intellectual and theoretical prowess is symbolized by the inkwell and manuscript page on the table behind arm.

The Cambridge exhibition considers that these are ordinary tools, altered by Vesalius, a testament to his manual dexterity. He didn’t need “fancy” instruments, but could use commonly available ones. I wonder about this interpretation, though. Given how many tools even today are shared — and altered — by many crafts, I wonder how many specialist instruments were made only for surgeons. There is no mention of this kind of specialization in J.B. Himsworth’s 1953 The Story of Cutlery, Although it is an excellent resource, it is far from comprehensive.


Detail: Title page, Vesalius, De humani corporis fabrica libri septem, 1543. Source:https://www.nlm.nih.gov/exhibition/historicalanatomies/Images/1200_pixels/Vesalius_TitlePg.jpg


Vesalius, De humani corporis fabrica libri septem, 1543, xii. Source:https://www.nlm.nih.gov/exhibition/historicalanatomies/Images/1200_pixels/Vesalius_Portrait.jpg