Monday, 28 April 2008

On silk yarn - what every weaver should know!

I was going to write about this very useful book a couple of months ago, I took the photo but didn't get much further than that. At the time, there had been a discussion on the Weavetech discussion list about identifying what type of fibre was used in a yarn by carrying out a burn test. This book includes burn test information.

It is:
Handbook of Textile Fibres, by J Gordon Cook B.Sc.,Ph.D.,
published by Merrow Publishing Co. Ltd, first published 1959, 2nd ed. 1960.

I found my copy at a secondhand book fair, and bought it because it looked useful, although I had not heard of it. My copy has parts 1 (natural fibres) and 2 (man made fibres) in a single volume, I just looked on the Abebooks web site and found that some of the copies offered are just part 1, or part 2, and that it seems to have gone on to a 5th edition (1984). Prices start low, at around £4.

This book is a superb reference book. It's a great book to dip into, or to look something up, but there's so much information in it that it's not the kind of book that it's easy to just sit down and read. Because of that, I'd had it a while before I really got to understanding and appreciating it's value. In fact, I do recall at one time wondering why I'd bought it! But I did buy it a few years back, some time before I started spinning and weaving. Now, I find it is invaluable.

Why? Well, for example, there are 35 pages about wool . There's a brief history of the wool trade in England then all you might want to know about wool production and processing, physical properties and behaviours, chemical structure and rather more besides.

For example, did you know that "Wool... can be curled by coiling it round a rod. If it is placed in boiling water and cooled it will remain in the form of a spring. It is acquired a permanent set."? This happens because water attacks wool keratin and can cause changes in the chemical structure. Did you know that as wool absorbs moisture it generates heat? And that it releases the water it has absorbed very slowly and gently, which means that you don't get sudden cooling?

There's also extensive information about insects that attack wool, about shrinkage and felting (what happens and why) about washing. Here's some information on washing wool - the ideal temperature is about 100 degrees fahrenheit / 38 degrees C, and the best technique for washing is a process of soaking and squeezing - avoid agitation, tumbling and stirring. And another notable fact - handknitted yarns benefit from a residual tendency to felt, helping the knitted garment to hold its shape.

There is similar information in the book about other fibres, so it's good to compare and contrast and for understanding the relative properties and uses of different fibres.

By now you will be wondering why on earth the title of this post is silk yarns!

Answer, it's because this is what I was looking up last week. I needed to find out about: the different types of silk yarn, how they are made, what their different properties are, what might make a good warp yarn.

I also referred to:
A Silk Worker's Notebook, by Cheryl Kolander, pub. Interweave Press 1979, revised edition 1985

Silk, Luther Hooper, Pitman's Common Commodities and Industries Series (1930's? no date given)

From Fibres to Fabrics, Elizabeth Gale, Mills & Boon Ltd., London, 1978 edition.

These are all good and useful books. Cheryl Kolander's book strikes me as rather a slim volume for everything she wants to include, and sometimes I wish she had taken more space and written more. It is a lovely guide book to have covering basic information of history and use, handspinning, caring for silk, and has appendices with notes on weaving and knitting.

Luther Hooper's book is about silk production, from the moth(s) that produce silk to factory processes, going through to weaving. It is a lovely and useful book, although I am writing more about the others today.

Elizabeth Gale's book is a text book, written by a textile designer, for use in schools and colleges, "to assist those who wish to know about textiles without going into the technology of the subject in great detail". It was this book sitting on my shelf that inspired my blog name!

From Cheryl Kolander, I learnt that there are two types of silk yarn, reeled and spun. The reeled yarns are "thrown". She says "throwing is the process of twisting the unspun filaments of reeled silk." Thrown silk produces fabrics "stronger and more durable than comparable fabrics of spun silk". She says the two most important types are organzine, a tightly twisted and plied yarn, and tram, which has only enough twist to hold it together and is used for weft.

She says that spun silk is comparatively modern, a means of making use of the waste from thrown silk, which had in former times been used as wadding to provide insulation. The machinery for spinning wool and cotton made possible the spinning of silk waste into yarn:

"Spun silk yarns go by many names, some refer to the fiber-length, some to the fiber's character, and some to the yarn's spin."

The list she gives includes tussah (wild silks), meche (soft, long staple, regular twist), shantung (slighty slubby), cord (twisted and plied), flourette (long staple, spun from combed fibres) bourette (short staple, spun from carded fibres of 1-2" length).

Elizabeth Gale says of spun yarn that "Long raw fibres are cut to a maximum length of about 30 cm and are spun as for worsted, and short lengths are spun like cotton."

I remembered Peg wrote recently about the behaviour of two different skeins of yarn she had dyed, one was oraganzine - so a high quality thrown yarn - and the other bombyx - possibly a spun yarn? This might explain very different behaviour, the two yarns are probably very different in construction and from very different fibre lengths.

I'd look after that organzine carefully, Peg. Cheryl's book tells me that "thrown silk yarns are rarely available to handweavers. This is partly due to their expense... partly due to the fact that thrown silk yarns are usually very fine, much finer than most of us are comfortable with."

Indeed, I have here my catalogue and price list from H.T.Gaddum & Co. Ltd, a specialist silk importer in Macclesfield, England, (tel: 01625 427666) generally regarded as the best source of silk yarns for handweavers in the U.K., and they offer only spun silks - which range from £40 to £64 (per kilo, excluding V.A.T. ) and textured silks.

(Another good source of interesting spun silk yarns is Texere Yarns, of Bradford, England.)

So, what about my little Handbook of Textile Fibres on the subject of silk? There's 20 pages, so it is not as easy to summarise as Cheryl Kolander's book. It even includes a short section on "spider silk"!

Looking at the types of silk yarn, however, thrown silk (the name coming from the Anglo Saxon word "thrawan" meaning to whirl or spin) is made from "multi-filament strands.. twisted together to form heavier threads", although sometimes weaving is done from the filaments as they are, without twisting them. I was interested to learn that the "natural gum, serecin, is normally left on the silk during reeling, throwing and weaving" because "it acts as a size which protects the fibres from mechanical injury". The weight of the woven fabric may reduce by a third when the serecin is washed out! The cloth before the serecin is washed out, which is dull in appearance, is known as "hard silk" and when dugummed as "soft silk".

The extra information about thrown silks in this book tells me that tram is made from two or three strands of silk, and could be low twist with 2-3 twists to the inch, or high twist with 12-20. It is of moderate strength. Oraganzine is very strong, 2-3 strands are twisted together and then the compound thread is twisted 9-30 times to the inch in the other direction. Very high twist yarns, 30-70 twists to the inch are known as crepe.

There's an interesting section on the spun silks:
"....the throwster is fortunate if he can make use of half of the available silk in filament form. The rest of the silk is unsuitable for reeling, and is know as 'waste silk".

"This waste silk is much too valuable to throw away, and it is used for making the yarns we know as "spun silk"......"
".....After dugumming... The silk is opened and loosened in a machine that delivers it in the form of a gauze-like blanket or lap. The fibres are then combed and sorted into length-groups, and then draw into rovings and spun by twisting so that the short fibres hold tightly together."

The section on silk ends, as with other fibres described in the book, by giving details of effects of sunlight, age, moisture, heat, chemical properties, electrical properties, effects of acids, alkalis and solvents.

Did you know...

- Silk can take up 1/3rd its weight in water without feeling wet to the touch,

- and wet strength is 75-85 per cent of the dry strength?

- It has less elastic recovery than wool, but better than that of cotton or rayon.

- Once stretched by 2% of original length, it will be permanently stretched.

- It will stand higher temperatures than wool, but decomposes quickly at 175 degrees C.

- It is a poor conductor of electricity, and gets a static charge in dry atmosphere.

- Silk is so costly that fabrics are often "weighted" with metallic salts to create artificial density, a moderately weighted silk could contain 25-50 per cent salt, heavily weighted 60 per cent. Weighted silks are not as strong and can deteriorate rapidly - e.g. perspiration will cause rot. But I don't think handweavers will be using this technique!!


neki desu said...

thank you for the Gaddum link. Now i know where to direct myself when i finish my silk stash.
Will that ever happen ? :)

neki desu

Leigh said...

I love your book reviews. Always so informative. Very interesting tidbits and recommendations.