First of all, what is a thrum?! For knit and crochet, a thrum is a short length of unspun roving that is worked into stitches along with your main yarn, leaving the ends of the roving loose. Usually these are placed evenly with the loose ends to the fabric back (WS), so they form a lining for extra warmth.
How to Make Thrums
Separate the roving into sections the approximate width of your finger. Pull off a section of roving approximately 6 inches long (does not need to be exact) and split it in half lengthwise. You will end up with a thin section of roving about 6 inches long.
Note: Do not cut the roving as it will not work well.
Fold each end of the roving toward the center.
Twist the roving tightly so the ends mix in with the middle section to create your thrum. Thrums should be about 3 inches long (does not need to be exact).
Pro Tip: Prepare a bunch of thrums ahead of time to make your project go quickly.
How to Add Thrums to Crochet
Insert hook into st into which the thrum needs to be added.
Fold thrum in half and place on hook.
Pull thrum through stitch
YO and pull main yarn through thrum and loop on hook. Tug gently to on thrum to secure it on the back of the work.
A finished series of thrums will look like this:
Thrummed Fabric Front (RS)
Thrummed Fabric Back (WS)
If you are interested in trying crochet with thrums, consider the Crochet Thrummed Mittens free pattern!