By Katrin on Thursday, 10 February 2022
Category: all the gory details

Gummy Silk - The Adventure Goes On.

Well, I definitely got your attention with the gummy silk thing yesterday!

First of all, here's a better picture of the two silks side by side:



Now to the answers to all the comments yesterday...

Jessica's comment was:


That's really interesting! And it probably explains the deep colours we see in medieval embroidery. And how they were able to do couching over padding with a relatively thin thread and still being able to force the gold threads into place and keep them there. How does this partly gummed silk compare to modern Chinese flat silk? That's my go-to silk for medieval projects as it produces embroidery with a slight wavey texture as seen in medieval embroidery.
The gummy silk is quite a bit stiffer than the de-gummed one. The flat silk that I know is much more prone to snagging on anything that looks like it might be rough, but I haven't been able to do a proper comparison with similar silks yet. The gummy sample was a bit of the Texel stocking silk, which is a four-ply silk with slightly twisted singles, the de-gummed was flat silk (my embroidery silk). I have flat gummy silk here, but it's much thinner than the embroidery silk. On my list is trying to make a thicker thread from it, similar in size to the embroidery silk, and see how that compares. That will involve some winding first, though, and fortunately-unfortunately I'm a bit too swamped with other things right now to sit down and do that.
My guess would be that the textures the gummy silk will result in will be a bit different from the degummed one, but how much? That would need some investigation...
Beatrix wrote:

I wrote an article a while ago where I came upon twisted medieval silk. This is from my article:
Lisa Monnas and Roberta Orsi Landini wrote on S-twisted silk threads: ´fourteenth-century velvets usually have Z-spun main ends…but from the late 1420s their [i.e. Italian velvets] main warp threads were generally S-twisted. In contrast Ottoman velvets of the late 15th and 16th centuries generally have Z-twisted main warp threads´ (Monnas 2012, 15); ‘the finest silk thread was used for the warp: strong shiny silk organzine, generally made up of 2 S-twisted ends’ (Orsi Landini 2017, 15-16).
Monnas, L. (2012) Renaissance velvets. London: V&A Publishing.
Orsi Landini, R. (2017) The velvets in the collection of the Costume Gallery in Florence / I velluti nella collezione della Galleria del costume di Firenze. Riggisberg and Florence: Edizioni Polistampa.
So even reeled silk seems to have been twisted - at least a bit.
There's definitely silk with twist - sorry if my post sounded like there was only the untwisted version. Organzine, which is a 2-ply from more or less twisted singles, is also still used today as fine silk for weaving. It's much less prone to snagging than untwisted single, and still has a very nice shine to it.
The silk with very little or almost no twist is an exception, usually there's at least a bit of twist in there. Some is already added (or can be added) when reeling it off the cocoons. Usually, that small amount of twist makes no difference whatsoever - unless you're doing something like the Albecunde belt, where there will be an optical difference between the two tablet turn directions. That belt only works as wonderfully well as it does. Embroideries also usually seem to use really flat silk with no appreciable twist, though a little bit of twist there will not have too much of an impact, at least according to my experiences - plus you can always twist the needle to add or remove twist if it does.

Finally, Florence asked:
How does one de-gum silk?
There's several different ways to do it; you can read more about how the process works here (where different methods used in the industry are given).

The classical method is to boil it off with soap, typically Marseille soap, which is based on olive oil. Which is also what I used for the de-gumming test I did today with a bit of the Texel silk.

[caption id="attachment_6739" align="alignnone" width="300"]

During the de-gumming process - it's starting to lose some of the colour to the soap soup.


It's hanging out to dry right now, so proper colour comparison may only come later. I'm just as curious as you are!

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