The Wool Journey Part 13: the bulking of wools

Sue Blacker's picture
28 February, 2019 - 21:04 | Sue Blacker

This photo illustrates the different fabrics obtained by knitting with Cotswold (on the left) and Shetland (on the right) - both as Double Knitting yarn.  So both yarns will have close yardage for the same weight and both will work up to the same tension swatch size for stitches and rows.  In this case both are also woollen spun - remember that worsted spun yarns work the same number of stitches but around 10% less rows in a tension swatch so you get less fabric, if more drape, for your yardage.

Now even if you look at the balls of wool you will see a considerable difference in appearance too.

Both these sheep are hill sheep although the Cotswold has a balmier climate than the Shetland in its heritage.

This effect is due to a series of factors already described in earlier Wool Journey episodes, and these include fibre length, nature of crimp, degree of lustre, and more!  However, a recent article in the Atelier Wools of Europe magazine No 27 has caught my eye - about the different bulking factors of the fleeces from different breeds.  Interestingly a completely separate piece of research done to create business plan I mentored, for making wool felt numnahs (the pad which goes under the saddle of a  horse) found that Suffolk was considerably better than other breeds, no doubt for the same reason.

So the way the bulking factor is measured is by means of a Bulkometer, a device invented in New Zealand.  Clean wool is put inside and then compressed ad release by a piston repeatedly for 30 seconds and the resulting volume is then measured.  Being New Zealand the results related more to the local breeds.  However the more familiar breeds are as follows:

  • Down 30-34
  • Cheviot 29-34
  • Poll Dorset 27-34
  • Merino 25-32
  • Texel 24-28
  • Corriedale 23-28
  • Romney 21-25
  • Border Leicester 17-21
  • Lincoln 17-21

The numbers relate to the cubic centimetres per gram obtained from the compression exercise.  For New Zealand, specialised in wools for carpets (as for the majority of the UK), the ability to recover bulk is obviously important as it will improve comfort.  This also works of course for pillows, duvets and stuffed toys, and then will also contribute to the recovery of knitted garments in wear - and of course to numnahs.  It does not necessarily imply hard wear or indeed any other qualities other than the ability to recover bulk.

So this is another interesting factor to consider when marketing yarns, but also when spinning and finishing them and of course in blending fibres to create a yarn with specific properties.



Submitted by Theresa Rogerson on
Any chance you could group all of the Wool Journey posts into a category on the right column? I would love to read them all from the beginning, but don't really want to scroll through the entire blog to find them. Thanks!

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