Q: I need my socks to keep my feet warm (but not too warm) and keep moisture from building up. What are the best fabrics, yarn types, and fabric structures for this?
A: It turns out that fabric structure is the most important factor in thermal and moisture performance of socks. Terry fabrics seem to have the best performance on a number of variables.
Five researchers published an article in the Textile Research Journal in 2015 examining a vast number of fabrics, yarn types, and fabric structures of socks.
They tested the following fiber types:
- Fine wool
- Mid-micron wool
They tested the following yarn types:
And they tested the following fabric structures:
- Single jersey
They tested ALL these types of fabric in many different combinations. For instance:
- Acrylic, single-twist yarn, terry
- Mid-wool, high-twist yarn, half-terry
They wanted to see each fabric variable’s effect on the following things:
- Thermal resistance (how well the fabric resisted getting hot)
- This also measures thermal conductance (how well the fabric transmitted heat away from the heat source)
- Water vapor resistance (how well the fiber resisted absorbing moisture from evaporating water)
- Water vapor permeability (how well the fiber lost moisture from being “aired out”)
- Liquid absorption capacity (how much liquid the fiber absorbed from a source)
- Regain (how much moisture the fabric absorbs under normal temperature and humidity)
Basically, this is about which fabrics handled heat better, and which handled moisture better, in ways you’d want in a good sock.
The experimenters used a fabric-knitting machine to produce 27 types of fabric with many different variables.
Fabrics were pre-treated to ensure stability. This means they were all washed in the same machine.
Then, each factor was experimentally tested in its own way:
- Regain (the amount of moisture the cloth absorbs in normal conditions) was tested by placing the fabric in a scientific oven at 105 degree Celsius until a constant mass was reached. Then, fabrics were placed in a more normal room temperature at a constant relative humidity and weighed again. The difference in weight is the amount of moisture absorbed from the air.
- Thermal Resistance (and conductance) was tested on a scientific hotplate by heating the fabrics up and measuring the degree to which heat was transferred from the hotplate through the fabric and to a cool plate on the other side.
- Liquid Absorption Capacity was measured by dunking each piece of fabric into distilled water for 60 seconds, followed by a 120 second draining period. Then, the fabric was weighed to determine amount of liquid absorbed.
- Water Vapor Resistance was measured by placing the fabric over a special porous plate above re-distilled, deionized water. As the water evaporated they measured how much was absorbed by the fabric.
- Water Vapor Permeability was measured by allowing the fabric to soak up evaporated water in a special test dish, and then spinning it on a turntable for one hour, weighed, and then six hours and then fabric was re-weighed. The difference is the amount of water vapor that was absorbed and then evaporated out of the spinning fabric (this simulates airing out the fabric).
Since they tested so many variables, the results were obviously quite complex.
The nutshell result is that the most important factor of all the ones tested (fiber, yarn type, structure) is Fabric Structure. Specifically, full terry cloth was the best performer of all types.
- Fiber and Fabric structure made the most difference here.
- Acrylic had the lowest regain of fiber types.
- Terry had the highest regain of fiber types.
- Thermal resistance:
- Fiber, Yarn, and Fabric structure all made a difference.
- Single jersey had the lowest thermal resistance of all fabric structures.
- Acrylic had the lowest thermal resistance of all fibers.
- High-twist had the lowest thermal resistance of yarn types.
- Water vapor resistance:
- Fabric structure made the most difference on this.
- Single-jersey had the lowest water vapor resistance of all fabric structures.
- Liquid absorption capacity:
- Fiber, yarn, and fabric structure all made a difference.
- Single jersey had the lowest liquid absorption of all structures (terry had the highest).
- Acrylic had the lowest liquid absorption of all fibers (mid wool had the highest).
- Single twist had the lowest liquid absorption of all yarn types (low-twist had the highest).
- Water vapor permeability:
- Fabric structure made the most difference.
- Single jersey had the highest water vapor permeability of all fabric structures.
- Thermal conductance:
- Fabric structure made the most difference, but fiber had an effect too.
- Single jersey had the lowest thermal conductance of all fabric structures (terry had the highest).
- Fine wool had the highest thermal conductance of all fiber types.
Terry cloths (no matter what fiber it was) were the most thermal and water vapor resistant, least permeable to water vapor, absorbed the most water, and conducted the most heat away from the heat source. These are all characteristics of a good sock.
However, the terry cloths were also the thickest and had the highest mass of all cloths.
Single jersey fabrics were thinnest, lightest, and had the least resistance to heat and moisture. They were also least absorbent and least conductive.
One of the interesting things is that the structure of the fabrics seemed to have a generally stronger effect on its properties than the fiber. Fine wool, mid wool, and acrylic didn’t differ as much as how those fibers were arranged (single jersey, half terry, and terry).
- For the most part, the fabric samples that had the best properties you’d want out of a sock were made from terry cloth.
- Fiber made less of a difference than structure.
Van Amber, R. R., Wilson, C. A., Laing, R. M., Lowe, B. J., & Niven, B. E. (2015). Thermal and moisture transfer properties of sock fabrics differing in fiber type, yarn, and fabric structure. Textile Research Journal, 85(12), 1269-1280. Link: https://trj.sagepub.com/content/early/2014/12/04/0040517514561926.refs