Great stuff you're puttin' up here. If I only had the time and the cool camera, I'd do you up some "real" waxends out of hemp, 18th c. formula wax, and genuine black bristle *sigh*. Maybe some day.
Anyhoo...
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"First, what is the difference between line yarn and tow yarn?"
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In a nutshell, flax stalk fibers are processed in a phase called "hackling" (as in getting your 'hackles up'), where it's dragged like a horse's tail, through long spiky things, like carding wool. This combs the long fibers and removes the short, broken, or bad bits. The waste that remains in the hackles--combed-out in other words--is called "tow", it's the inferior, lumpy, bumpy, weak, broken, and short bits. But, not to be wasted, it's spun into yarn as well for cheap goods. The good long fibers that are combed through the hackles are the "line" yarns--the good stuff. If these "line" yarns are then wet-spun, the flax fibers are softened with water (or spit if you're hand-spinning) and lay-up more smoothly and tighter, so the yarn has a harder hand or finish. "Line" yarn is the good stuff, "wet-spun line" yarn is the better stuff, and "tow" is the crap left behind.
As an aside, based on Jake's photos above, I took samples of perhaps 8 or 10 different single shoe thread samples to my textile "guru". Brands like Finnlayson's, York Street, and several varieties of Campbell's, and Barbour's, even old stuff going back 50 or 60 years. She un-twisted each, carefully pulled them apart down to the staple fibers, measured them and did her magic. The longest staples, and the strongest stuff she said was the Barbour's hard-finished threads in the little plastic jugs--longest staples and it's wet-spun. I've had no problem buying this product from AGS-CUDAS Shoe Repair Supply in Ashland, VA. I buy a case every 6 months or so. Try them. Their phone number ought to be on the Forum someplace.
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"Second, I've read that hemp is better for inseaming and stronger as well...Yay? Nay?"
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Here we've got that problem of what's "hemp"? In the 1700s and into the 1800s, "hemp" thread was made from the cannabis plant (whence "canvas" when woven into cloth), while "flax" thread was made from the flax plant (whence "linen" when woven into cloth, and "linseed oil".) At some point later in the 19th c./early in the 20th c.(???), these terms lost specificity, and the shoe trade started calling unbleached gray, flax thread "hemp", and calling the whiter bleached flax thread, "flax" or "linen" (rather strange since linen is a woven cloth made from flax, but never mind). Cannabis "hemp" thread would be very strong, possibly stronger than flax, and less prone to rotting, which was why it was cultivated and preferred for ships' ropes and canvas sails, etc. After shoe threads were all made from flax, the unbleached gray thread called "hemp" would be stronger (bleaching weakens the fibers), while the whiter "flax" or "linen" threads would be weaker.
So it depends what you mean by "hemp"? Cannabis hemp, or the later unbleached flax "hemp?
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" I have some 20/1 line hemp that came from a friend. I don't know where he got it, but it may be available."
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Short-term memory they say is the first to go
That 20/1 wet-spun line yarn (flax "hemp", i.e. unbleached flax, not cannabis) came from me, and was purchased from a weaving supply house in Massachusetts called Webs. I bought a bunch of it once, and have no idea if Webs is still in business. One could do a search if interested. I wouldn't use a size 20 for inseaming, just for closing uppers, which we do by-hand down here. A 3-5 cord waxend made from the 20/1 is just fine for that. For inseaming and sole stitching I go up to a 10/1, or a "#10", like the little balls are marked.
Here endeth the lesson. Good luck.
