Here, you can see a comparison of a teflon bone folder I’ve been using for seven years at the time the picture was taken, and an identical new one. Of all the types of bone folders I have tried, teflon remains my favorite material since it’s the only one soft enough to not leave any marks even on delicate papers. The softness also comes with disadvantages, however. Teflon bone folders wear away visibly. The wear is not uniform: usually, narrow furrows are created in some places, and then they tend to become deeper and deeper since during folding, paper aligns with them and wears those places even further. For very thick papers, such as 200+ gsm cardboard I sometimes use for making big models used during workshops, this wear is so extreme I prefer using bone folders made from stronger materials (bone, wood, plastic). Furrows created on the bone folder can be cleaned away by polishing. When they are small, it is enough to use a slightly rough surface, such as the glazed side of a ceramic tile. For deeper damage, I use sand paper of various grits. Thus, the visible shortening of the used bone folder is an indirect result of it being used to crease paper, but not all material is removed by the paper itself. Still, it is interesting to see how over several years, very small changes resulting from creasing and polishing can accumulate into a change that’s clearly visible.