Related to this: one thing I’ve noticed is that a lot of so-called donegal fabrics achieve the speckled effect by using nylon threading. “True” donegal, sourced in County Donegal, Ireland, would be pure wool but it’s common to find donegal-woven fabrics to use some degree of synthetics as part of the composition.
Interesting read. I personally avoid acrylic 100% of the time. Polyester and nylon are great for workout and tech gear/clothing. The addition of Elastane in pants has been mostly a good thing, I think.