We were looking at wool pants in Needless Markup the other day, and saw some things that dramatically contradict some points in JM's IS. It is time to list my issues with that book.
p28: Dyed wool has been scoured. If you see a blue fisherman's sweater, it was knit from scoured wool. The seamen/fishermen on the great Norfolk fishing fleets of the 14th century wore blue sweaters. The oiled wool was a result of oil being added after knitting.
Making textiles from wool in the grease is a matter of ignorance either of the textile worker or the end user. Prior to 1780, the countryside was full of textile workers that knew spinning was faster, and a better yarn was produced when working with clean wool. This is not to say that today some end users do not want wool spun in the grease. Every fashion house sells expensive garments made of impractical fabrics. Wool spun in the grease belongs to that class of expensive, impractical, fashion objects.
p55 All dry, naturale textile fabrics release heat as they are dampened. Both cotton and linen will release more heat than wool. However, damp cotton and lined will wick moisture to your skin, where heat from your body will evaporate it causing the linen or cotton to feel cold. Damp wool does not wick water, and the wool reflects heat from the body back to the body making the wool feel warm.
p64: No mention of differential rotation speed.
p64: Worsted yarn and woolen yarn are both as heavy as their grist dictates. Worsted yarn is denser. If I spin a pound of woolen yarn and a pound of worsted yarn at 5,600 ypp they will both be the same weight, but the woolen yarn will take up more volume. Both yarns will be the same length, and thus about the same amount of yarn will be used for a knitting or weaving pattern.
The fibers in the worsted yarn will be closer together than in the woolen yarn.
There is "thermal inertia", which more a factor of your body than of the textiles around it. And there is thermal insulation, which reduces heat loss or heat gain. Air does not provided "thermal mass". That is an error in JM's physics that was not caught by the editors/reviewers at Interweave. Thermal insulation is what textiles provide. Heat loss can be by heat advection in air, conduction, radiation, or heat advection by water vapor. To insulate against heat advection in air, one needs to stop air moving from the skin outwards. This is almost always the big source of heat loss, and it is prevented by tighter fabrics.Worsted yarns are tighter constructed and threrefor allow less air to move through them. Air molecules are tiny compared to wool fibers, so the wool fibers need to be very close together. If you want to trap air in the fabric, then the wool fibers and wool threads need to be on the order of 40 microns apart. Yes, trapping air does work, but wool fibers must be very close together to make that work well. Wool fiber that are 40 microns apart will work well to insulate against conduction. To insulate against heat radiation, you need to make sure that there are no gaps in the fabric. A test is to face a bright window and hold the fabric up 1" in front of your eye. If you cannot see an outline of the window than the fabric will insulate against heat loss by radiation. Such a fabric will also insulate against heat loss by advection in air. Wool does not wick water to the skin, thereby reducing heat loss as water vapor. In wet weather, this can be a huge effect.
If you want a nice warm wool cloth, try a wool flannel with worsted warp and woolen spun weft. No, my dear, warmth is related to how close together the fibers are rather than how they are fabricated.
p82:In weaving, the weave will lock the yarn in place - 2-ply is not required. Many of the great textiles of old were made from single ply yarns. Today, 2-ply is used because we do not need the fill for warmth and we do not full the cloth. And, single plies are harder to handle - and she does not want to open that can of worms.
p28: Dyed wool has been scoured. If you see a blue fisherman's sweater, it was knit from scoured wool. The seamen/fishermen on the great Norfolk fishing fleets of the 14th century wore blue sweaters. The oiled wool was a result of oil being added after knitting.
Making textiles from wool in the grease is a matter of ignorance either of the textile worker or the end user. Prior to 1780, the countryside was full of textile workers that knew spinning was faster, and a better yarn was produced when working with clean wool. This is not to say that today some end users do not want wool spun in the grease. Every fashion house sells expensive garments made of impractical fabrics. Wool spun in the grease belongs to that class of expensive, impractical, fashion objects.
p55 All dry, naturale textile fabrics release heat as they are dampened. Both cotton and linen will release more heat than wool. However, damp cotton and lined will wick moisture to your skin, where heat from your body will evaporate it causing the linen or cotton to feel cold. Damp wool does not wick water, and the wool reflects heat from the body back to the body making the wool feel warm.
p64: No mention of differential rotation speed.
p64: Worsted yarn and woolen yarn are both as heavy as their grist dictates. Worsted yarn is denser. If I spin a pound of woolen yarn and a pound of worsted yarn at 5,600 ypp they will both be the same weight, but the woolen yarn will take up more volume. Both yarns will be the same length, and thus about the same amount of yarn will be used for a knitting or weaving pattern.
The fibers in the worsted yarn will be closer together than in the woolen yarn.
There is "thermal inertia", which more a factor of your body than of the textiles around it. And there is thermal insulation, which reduces heat loss or heat gain. Air does not provided "thermal mass". That is an error in JM's physics that was not caught by the editors/reviewers at Interweave. Thermal insulation is what textiles provide. Heat loss can be by heat advection in air, conduction, radiation, or heat advection by water vapor. To insulate against heat advection in air, one needs to stop air moving from the skin outwards. This is almost always the big source of heat loss, and it is prevented by tighter fabrics.Worsted yarns are tighter constructed and threrefor allow less air to move through them. Air molecules are tiny compared to wool fibers, so the wool fibers need to be very close together. If you want to trap air in the fabric, then the wool fibers and wool threads need to be on the order of 40 microns apart. Yes, trapping air does work, but wool fibers must be very close together to make that work well. Wool fiber that are 40 microns apart will work well to insulate against conduction. To insulate against heat radiation, you need to make sure that there are no gaps in the fabric. A test is to face a bright window and hold the fabric up 1" in front of your eye. If you cannot see an outline of the window than the fabric will insulate against heat loss by radiation. Such a fabric will also insulate against heat loss by advection in air. Wool does not wick water to the skin, thereby reducing heat loss as water vapor. In wet weather, this can be a huge effect.
If you want a nice warm wool cloth, try a wool flannel with worsted warp and woolen spun weft. No, my dear, warmth is related to how close together the fibers are rather than how they are fabricated.
p82:In weaving, the weave will lock the yarn in place - 2-ply is not required. Many of the great textiles of old were made from single ply yarns. Today, 2-ply is used because we do not need the fill for warmth and we do not full the cloth. And, single plies are harder to handle - and she does not want to open that can of worms.
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