interesting that sandpaper was mentioned. I have a black badger knotted brush. Black is cut on the tips to shape the knot. It’s very scratchy when new. I spent 15-20 minutes whirling the tips around on 400 grit silicon carbide paper. This made the brush much softer at the tips. I haven’t looked at the magnified tips but I like to imagine that the spiky ends are now slightly rounded.
Of course, this method would ruin a high quality knot where the art is to have natural tips presented in a smooth fan or bulb knot.
Of course, this method would ruin a high quality knot where the art is to have natural tips presented in a smooth fan or bulb knot.