I am looking for a good method to measure the thickness behind the edge. It is because I am planning to investigate the relationship between the blade geometry and sliceyness myself. It is not hard to measure it with a micrometer, when the edge is thick. But below 0.01", it becomes quite difficult to put the micrometer to the right place, partly due to my presbyopia. So, I tried an alternative method. I took pictures of the edge from above along with a ruler using my iPhone at the highest zoom. (I first verified the accuracy of the ruler using a certified microscope reticule slide.) The ruler was lifted to a similar height to the edge bevel. The focus and exposure were adjusted to the ruler and fixed. I used the burst mode to take 10 consecutive images. Then, on the computer, I aligned the images and sum them to intensify the signal (using ImageJ freeware). With right lighting and focusing, I could clearly see the transition points from the edge bevel to the primary grind. Then, I determined the length of a millimeter (or a few) in the image and computed the "thickness" of the edge bevel. The values I got were quite consistent with those I previously measured using a micrometer, at least for thick edge knives. With this method, I can measure very thin edges at 0.003". You just need a camera, a holder to keep the camera above a blade, a ruler, and a platform to lift it. I think it works for now. But I have seen microscopic measurements of edge thickness using some kind of molding. That looked great and must be more accurate. Anyway, if you know a better way to measure the thickness behind the edge, please let me know.