Wool will shrink with washing and pull away from the denim.
I’ve wet and dry felted for 40 years.
I may have to stitch around the edges of a cellulose/poly patch by hand, but I’ve been needle felting cellulose for a few months, now and it is responsive.
I did a needled wool patch I wet felted and then needled on to acrylic felt that has held up after hand stitching to denim, but it is showing wear after several wash/dry cycles.
I have also been working with silk on wool on acrylic needle felt for several months (acrylic won’t distort with working, the wool provides a substrate, the silk is translucent and reflective and it also tends to form long straight strands). Very strong, too. I don’t wet felt these as it flattens the effect of light I am after. The cellulose handles like silk and is also quite strong. I know the polyfil will really compact if I use a multi-needle tool.
All non-wool fibers do dull the needles quickly, though.
—”All non-wool fibers do dull the needles quickly, though.”
I attempted repairing a comfortable Herman Miller chair by needle felting over the wear spots on the front of the seat cushion.
The seat and back are one-piece with a welt at the side/top edge. No easy way to open it up and sew on a seat cover.
It quickly abraided away.
Next, a nice bit of felted wool coat covering the top of the seat, lasted a few months and became loose on the edges.
Finally, I hand sewed the cover down, in places the factory adhesive holding the fabric to the foam was extra thick and I bent the curved needle stitching the cover down, using a needle holder.
That was two years ago and still holding.