^ My shiny (or actually pretty crude) new slate ulu. This style of knife was in common use among the Inuit people, and some other tribes of ancient peoples developed the same thing independently. Please note that the edge is already chipped from overly aggressive grinding.
^ This piece of slate broke so that one side was extremely thin and the other side rather fat. I'm not sure if this was ever capitalized on historically, but it works out pretty nicely I think. The finer edge tapers down between 1/32 and 1/16 inch and should have excellent slicing potential, while the fat side is more obtuse and far stronger to resist chipping.
^ Today's victims. A ripe tomato, some horsewed, and a milkweed stalk. This represents a nice cross section between soft, stringy, and firm natural materials.
^ Tomato: complete success using thin end of blade. The ulu did not push-cut easily, but a draw cut sliced aggressively. I expect that if you looked at the edge under a microscope, you would find it absolutely covered with tiny serrations.
^ Horsweed: poor. Using the heavy side to rock through these tough, stringy stems was getting the job done, but more by focused mashing than by cutting. The thin edge of the blade cut, but only with some sawing.
^ Milkweed: good. The thin edge of the blade was used to slice off the leaves and then the heavy side was used to do a rocking cut through the stem. This time the firmer and less stringy material yielded cleanly.
^ A sharpening stone to maintain the edge. This naturally formed flake had a very smooth convex surface and the stone is composed of some kind of hard conglomerate. The makeup of the stone is really ony appreciated when wet.
^ Running the sharpening stone against the edge, lightly, from side to side. This grinding is done wet to prevent dust formation.s