Wednesday, August 13, 2008

Threads of silk and gold

String theory, part 2

In my previous post, I focused mostly on plain silk, which seems to have been the thread of choice for medieval rosaries, and discussed some of the reasons it breaks. Here I'm going to discuss other types of silk thread, including silk with gold.

Since the biggest problem with silk thread is weakening by abrasion from the beads sliding along it, you'd think that people would choose threads that wouldn't be harmed by abrasion. Not so, apparently. I have seen a number of references to beads threaded on, for instance, "crimson silk and gold." And -- if I had any doubt that the gold was actually part of the stringing and not just decorative -- King Rene d'Anjou had a rosary "strung on a cord of silk and gold thread."

Before the days of plastic coatings it wasn't easy to make gold thread, or even imitation gold thread. Gold is a soft metal, and while it's possible to make a very thin gold wire that can be woven like thread, it is rather fragile and breaks when repeatedly bent back and forth. In embroidery it was mostly laid on the surface of the cloth and held down with stitches, rather than being threaded into a needle and passed in and out of the fabric.

Gold wire is also very heavy and expensive, so ways to make a thread that was lighter and more affordable were invented early. In the Middle Ages and Renaissance, most gold thread was made by beating gold very thin, cutting it into strips, and wrapping the strip in a spiral around a "core" thread, usually yellow silk. The silk core made the thread much more flexible and less breakable.

On the other hand, the actual gold coating on the thread was quite thin. This meant that while the thread would bend readily and you could, with care, actually pass the thread through fabric, its tolerance for abrasion was still very limited. In embroidery this thread was still mostly laid on the surface of the cloth and stitched down (called "couching"). I have difficulty imagining why anyone would thread beads on something this easy to damage -- yet clearly it was done.

A fragile thread might be made somewhat sturdier if it is not simply twisted, but actually braided or woven. I started out using ordinary silk twist to string paternoster beads with, and I think that is one reason I've experienced so much thread breakage -- especially because I haven't plied my own from reeled silk, but used commercial twist from machine-spun silk. (The Japanese Embroidery Center has been recommended to me as a source of reeled or "flat" untwisted silk.)

As with any fiber, the first step is to make a single thread out of collected fibers. Silk twist is the next step in processing, where two threads -- each composed of many fibers -- are twisted around each other. I suspect that this results in relatively long stretches of fibers being exposed to wear between the places where the threads twist around each other. The twist also does not exert a great deal of pressure on the individual fibers or prevent them from moving. My guess is that this means that when a few fibers are abraded and break, the breakage has a good deal of freedom to spread to other nearby fibers as they take up the load released by the broken fibers.


A compound thread that is braided or woven, on the other hand, has much shorter exposures of fiber, and the intersections where groups of fibers go over or under each other are generally tighter and exert some pressure to keep the fibers from moving. So we might expect slighly better survival of threaded paternoster beads strung on braided or woven thread. I'd be very cautious about generalizing from the very few examples that exist, but indeed I'm aware of at least two surviving strings where fragments remain of a braided or woven cord. (Of course there are also surviving bits of twisted cord, so I wouldn't call the question settled.)

One is this set of 15th- or 16th-century jasper beads from Salzburg, which -- if I remember correctly -- were found on a length of pink silk cord that had been tablet-woven.


Tablet weaving, or card weaving, is a technique usually used to make narrow flat strips by a technique that combines twisting and weaving threads together. It's an ancient technique and quite common in the European Middle Ages and Renaissance. A slight modification of the technique produces a round woven cord with a hollow center.

Simple braiding is of course another very common techique for producing cord. I was particularly charmed to discover "whipcord braiding," which uses two people and four hanging bobbins to produce a round four-strand plait very quickly and easily. (There's a YouTube video here.) I think we tend to under-estimate how many period techniques were done with two or more people cooperating, since as modern people we are more likely to produce our crafts alone.

A third technique, which was common in the Middle Ages and Renaissance but largely forgotten in modern times (until its recent revival), is called "fingerloop braiding," and uses (as you'd probably guess) loops of thread carried on the fingers rather than straight cords with loose ends. It can be very fast, and produces fascinating, intricate patterns. It's pretty much limited to making short lengths of cord -- a yard or two at most -- but for the length you need for a paternoster, that's no problem.


Just last weekend a friend for whom I've made a paternoster commented that hers needed re-doing and she was planning to make a fingerloop braid for them. I've also made a copy of my "Magdalen" beads for another friend (seen above), also with a fingerlooped cord. I'll be interested to see whether these wear better and last longer, but I suspect they will.

Posts in this series:

String or Nothing
The thread thread
String Theory
Threads of silk and gold
Of flexwire and time machines


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