The shirt is discussed in detail in Patterns of Fashion 4, and there are good photos of the ruffle and edging on p21. The cord at the edge of the ruffles appears to be a 4-strand plait, in brown (perhaps originally black) and white silk. There's a photograph online here.
At the chest-making workshop at Easter 2013, Llewelyn and Katherina set out to determine the structure of the cord at the edge of the ruffles, and come up with a way to reproduce it efficiently.
First, we messed around with coloured cotton and impromptu bobbins to reproduce the structure. Then, having got the structure working in a 3D pattern with four hands, we "flattened" it, to produce the same structure using two hands, and the terminology and movements of bobbin lace.
The pattern, using bobbin-lace terminology, is this:
- cross inner pair only
- cross both pairs
- twist inner pair only
- twist both pairs
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If the initial arrangement of colours is ABBA (as in the diagrams above) the pattern will be longitudinal stripes of each colour, as in the Sture shirt.
If the initial arrangement of colours is ABAB the result will be a spiral.
Because each bobbin is repeatedly turned in the same direction, the bobbins that "twist" will get a little more Z-twist, and those that "cross" will get a little more S-twist. Depending on the direction in which the threads used are spun and plied, this may result in one element of the pattern appearing fatter than the other.
I found this a very efficient way to make strong, decorative cord. With a small amount of practice, I could produce several inches in a minute.
You need to keep the cord under tension (lateral, rather than longitudinal) while you're producing it. That's easy if you only wind a small amount off your bobbins at a go. I usually work with 1-4" of free thread between the bobbins and the already-worked cord.
Once done, it still unravels somewhat easily (especially in silk). If you're using it as lacing cord (rather than sewing it onto something) you'll need to secure the ends with a knot, glue, or wax, and probably add aglets.
Update:
Here is a mid-17thC image of a woman using what seems to be a similar technique (or the same technique) to make cord with four bobbins, in a detail from Guido Reni's "Education of the Virgin", 1642. I'll have to try the crossed-stick arrangement to get a fixed point, and something to wind the finished cord onto. Thank you to Vettoria di Giovanni da Verona for sending me this link.
The detail is from the website "English Civil War (ECW) Living History Resources".