I was going to put this up last Thursday but somehow it's already Monday. Not quite sure how that happened! The nice part is it's now perfectly timed so that you can cast on a fun thrummed project — I just released Cadeautje, the third pattern in the Knitworthy collection.
Use a non-superwash wool that feels nice and soft to you. It's important not to use a superwash fibre because over time you want the thrums to felt together on the inside into an even blanket. Superwash fibres won't felt together and could fall out. Merino, BFL and Shetland are all ideal and easy to find. It's easier to make the thrums from combed top but carded batts or roving will give a lovely fluffy effect once you manage to separate somewhat even pieces!
Hold the end of the fibre in one hand and grip further down the length with the other, hands about shoulder width apart. Gently pull to separate a length around 8" long.
Pinch off a wee bit of fibre from this length — about a 1/4" wide. Pull the ends gently to tease it and fluff up the fibres a bit.
Fold the ends into the middle so they overlap just a bit.
Keep repeating this process until you have a nice big pile. They go fast once you start incorporating them into a project and stopping to make them one by one is no fun.