Pluck off a quantity of the fuzz, and put it in bleach. If it’s wool-only, or blended with silk or oil-based synthetics, the fuzz will completely disappear. If there’s some trace fibre left, it’s blended with a plant-based fibre.
I find wool-cotton blends to be rather heavy compared to pure wool or other wool blends, and they feel cooler to the touch. YMMV.
If you’re doing this at home, you can distinguish fibres using the burn and bleach tests. Note that it can still be quite difficult to identify the fibres in a blend.
Burn test:
How to tell what the fiber is advises using a 1/2″ square of fabric held in tweezers,and a bunsen burner. I’ve used 6″ lengths of yarn and a Zippo lighter, over a damp cloth.
Bleach test:
Use neat bleach in a non-reactive vessel (e.g., glass), and submerge the sample for 24hrs.
Quora linky.
thornmaiden.com 