This process is fairly well documented in several YouTube videos, but having done it myself a fair bit, I wanted to add or clarify a few details that the videos glossed over.
Spinning methods.There are three main methods of spinning twine, and like the gears on a bicycle, they're a continuum of the tradeoff: easy vs fast. Here are some videos that are good examples of each
- Bushcraft On Fire (one of the best. Hand over Hand, uses yucca)
- Silver Fox (countertwist, using nettle)
- Karamat (very good example of thigh rolling, uses willow bark)
Counterspinning is somewhat harder, and somewhat faster. It requires both hands to twist the twine in opposite directions, but there are no exchanges between the hands, so you're always making twine. Also, the twine itself hangs freely in the air between your hands, so it may not be as tight a spin as you would get with hand over hand.
Thigh rolling is definitely the hardest. It doesn't always involve your thigh - it needs a smooth, flat mildly frictional surface. A human thigh (sans hair) is an excellent choice and almost everyone has a couple within easy reach of their own hands. Thus the name.
Which one you use depends a lot on how much twine you make in your lifetime. If you just want an inch or two of twine to show your friends, hand-over-hand is your friend. If you're doing a single project and need a yard or so of twine or even doubled twine, counterspinning may be the way to go. If you think you might make twine on more than three days in your entire life, taking the time to learn how to thigh roll is definitely worth it.
Update (11-Feb-2014) The folks at Stone Age Skills report being able to thigh-roll 3 meters of 4mm rope out of yucca fiber in 15 minutes.
Working with yucca
Scraping off the green stuffThe top side of yucca leaves is a continuous, smooth sometimes shiny surface. It contains none of the fibers, but serves as a sort of gluey mat to which they bond. Scraping it off with a nearby stick or rock is not hard after your second or third try. You can do this step with your thumbnails if you need to, but that's more effort. The only real danger is pressing down fiercely and breaking some of the fibers.
|Top: A scraped section of leaf next to a pile of the scrapings
taken from it.|
Center: A more heavily scraped section of leaf.
Bottom: The scraping has gone to the point of separating the fibers.
Above, you can see progressive examples of thumbnail-scraped yucca. I try for something like the bottom example. A few broken fibers is not a problem, but every broken one probably sits adjacent to two more that are almost broken, and when they are incorporated into the twine, they will break under stress, making the twine weaker. Thus the loss is slightly worse than it appears. Going much beyond the third example will give a lot of damaged fibers, and a potentially weaker twine.
Not all the videos cover scraping, and since yucca twine (of thicker fibers and lower quality) can be made skipping this step, that explains the absence. On the other hand, with a dull straight edge, it's very little work in exchange for much finer fibers, so I think it's worth it.
Drying before spinningThis is way more important if you skipped the scraping step. After a few days in the fresh air, disconnected from the yucca plant, the leaves will shrink (across the leaf) substantially - sometimes as much as 40%. If you spin undried, unscraped yucca fibers into twine, the twine will be mostly useless within 48 hours, due to the twists unravelling. The fibers themselves are getting narrower, and need more twists to stay together. But your twine was spun before the shrinking. Now the curls just stand empty, like this:
|Spun fresh: left, dark green|
Spun dry: right, light green