I hear that some are now teaching that for woolen prep, the fiber should be fed into the drum carder -- cross ways!!
Feeding fibers cross ways into the carder will result in (some) fibers that are parallel to the direction of drafting after the rolag is formed and this will result in a semi-woolen yarn. Semi-woolen yarns are stronger for less twist than true woolen yarns, but have less loft. The lower twist requirements are a real advantage when working with a spindle or slow wheel – or for weft. They are not bad yarns, they are just different.
There is certainty nothing inherently wrong with semi-woolen yarn. In deed it has great virtues, such requiring significantly less twist to form a competent yarn. However, it is not woolen and will never have the loft of a true woolen preparation yarn. If I were a teacher facing a class with rather slow wheels, I might will very well teach feeding fiber into the carder crosswise because it would let the students produce more yarn faster and that will make them very happy. the teacher is betting is that nobody will look at the yarn they spin and announce "This is only only semi-woolen, not woolen.". A textile judge would simply rank it as "less lofty".
Thus, in using the drum carder to make rolags for woolen spinning, I think the fiber should be fed in parallel with the rotation of the drum. The batts that I make rolags from are fragile and easy to split lengthwise if I take them off the swift, but as the rolag is rolled, all the fibers are at approximately right angles to the direction of drafting. and yes the rolags are fragile. See
( http://ssa.nls.uk/film/1129 ) at minute 5:58. The rolag is very easy to pull apart if elongated without twist. As the rolag is elongated in drafting under twist the fibers spiral into the yarn producing the loftiest yarn, but requiring a lot of twist to make the yarn competent. For very light and lofty woolen yarns, I use the cotton cards on fine fiber to make long white clouds of nothing. These draft and spin into a very lofty yarn. Somehow, hand cards seem to be able to produce lower density rolags than I can make on the drum carder. Spinning fine woolen yarns requires a 30% more twist then the same grist of semi-worsted.
Feeding the fiber in parallel with the rotation of the drum, and then dizing off to form roving will produce a semi-worsted yarn, which has lower twist requirements, but has less loft. On the other hand it is a much more economical use of fiber than true worsted, particularly in applications like knitting and weft.
True worsted requires combing. Combing removes all the short fibers. Worsted spinning produces the strongest, most durable, smoothest, and for long wool, the most lustrous yarns. Worsted spinning requires the least amount of twist for the grist, but low grist worsted yarns are harsh and unpleasant. Thus true worsted needs to be spun high grist . If a thick yarn is wanted, ply a lot of fine singles together. Thus, worsted has a very high total twist in the finished yarn. Such yarns are a large effort on a slow wheel. Combing also result in large losses of fiber prior to spinning. Thus, true worsted yarn is very expensive. Worsted is best worked on long wool, so the waste is not ideal for either felting or woolen spun yarns.
The bottom line is that true woolen and true worsted spinning want a lot more twist than the “semis”. As a spinning teacher, facing a class of students with slow wheels, teaching semi-woolen and semi-worsted is the option of least resistance, and there is a tendency to fudge the terminology. It is hard to tell a class of new spinners that they need to discard the shorts out of their rather expensive top in order to make true worsted. It is easier to just have them spin semi-worsted. My point is that if one looks at sweaters in “Needless Markup” on Union Square in SF or 3 Bags Full in Santa Monica, a nice sweater from semi-worsted yarn is $800, while one with the gleam of true, finely spun, worsted yarn is $5,000. For an artisan spinner the difference is 30% extra fiber waste and 40 more tpi (more and finer plies) in the finished yarn.
I am not saying that one should attempt to hand spin worsted yarn for the fashion houses of Paris and Rome, I am saying that the gleam of fine worsted spun yarns has an artistic and aesthetic appeal that sometimes makes the effort and expense to spin true worsted worthwhile even if its other properties (warmth, durability, resistance to felting, . . .) are not required.
In my case, spinning the yarn for a 5-ply sport weight sweater worsted, rather than semi- worsted takes an additional pound of fiber. Spinning 4-ply jumper weight as true woolen takes an extra 12 or 16 hours of spinning. On the other hand, if I have a good supply of long wool and "Viking" combs (rather than cards) it is faster and easier to spin the yarn as worsted. I think that on those harshly cold islands they sometimes did things the easy way.
Today, we think of Fair Isle as always knit from woolen or semi-woolen yarn. However, there is no reason why a modern artist cannot incorporate the luster and gleam of worsted spun yarns into Fair Isle style knitting patterns.