The burr is often a troublesome factor for those new and sometimes advanced sharpening enthusiast. A burr is a plastic deformation of metal at the apex of the cutting edge, think of it like a mud slide down a hill but the metal that does not get ground off forms itself to the edge extending slightly past the apex. The burr is often referred to in sharpening is two different ways, the first being a coarse sharpening burr that helps you to judge when a worn or damaged bevel has been realigned. The second and often problematic one is the one that comes in the final stages of sharpening and unless you know what your looking for can often be missed. Sometimes "chasing" the burr can lead to more problems than solutions, when using a coarse stone to change the angle or fix damage to the edge pressure and the want for speed usually are our biggest enemy. More often then not we use more pressure than needed on a coarse stone because when we do it cuts into the edge faster making time spent working on the knife shorter. In reality though you end up making more work for yourself in the end, using too much pressure causes a higher degree of plastic deformation and often difficulty's in holding a precise angle. When light pressure and good angle control are kept you can let the stone work the edge and not the edge working the stone. Instead of trying to form the burr form the edge, as you sharpen work on holding the proper angle throughout the process and making them meet in the center. When done like this your angles per side are usually more even because your not grinding one side until it folds over the other angle on the opposite bevel and repeating. Picture example 1, ZDP-189 sharpened on a DMT XX-coarse benchstone. As you can see even at 120 microns you can achieve a almost burr free edge and what burr is their is in line with the edge and not the cause of increased angle. This next picture is a example of a burr caused by excessive angle to one side. Picture example 2, 420HC using a DMT fine 600 mesh benchstone, excessive angle applied to back side. 100x As you can see for example 2 the burr has now overtaken the edge and when felt will feel like the edge has rolled over and is very tough. When this has happened the angle to the side with the burr must be met to the angle of the side that has created the burr. The side with the burr will take only minimal passes to reform the burr back to the side with the steeper angle but now when you go back to the other side and try to push the burr back your angle exceeds the center line of the knife even more and continues to change angles per side of blade. Watching for angle change and amount and type of burr formation is a must if you desire a even and properly formed bevel. Now on to the finer side. When sharpening with fine grit abrasives your still creating this burr but instead of being able to feel it you must find it. One of the best ways if you don't have any magnification equipment is to look under bright warm lighting. Another way to tell is if you blade will only pass the shave test on one side but sometimes a burr can be too fine to even be noticed that way. Once you equal or surpass a 8000 grit finish the burr if any and if the edge has been formed properly is usually a mute point because the first time you cut something your probably creating more damage to the actual edge than the burr is resisting. Though if not formed properly edge retention and cutting performance can be pretty bad. Picture example 3, S30V sharpened on a lapped spyderco UF ceramic. Its not the best picture but you can still see the very small burr. pic at 400x enhanced picture from above I wish I could show more but until someone sends me a SEM this is as much as I can show ya. Hopefully this has been of some help and please share your comments.