3M 0.3 Micron Microfinishing Lapping Film Sharpen Sheet

Woodworkers have embraced the use of microfinishing sheets for "scary sharp" blade sharpening.

This 3M Imperial Microfinishing Film is designed for industrial applications and is not readily available for retail. These films use a high strength polyester film as a backing material. The abrasives are carefully graded and electrostatically oriented for greater cutting efficiently. Even grading is very important for even cutting. You get fewer scratches, and more particles of abrasive at the same grit mean that more of the sheet cuts at the same time - faster and more evenly. Unlike more common Wet-or-Dry papers, these papers are designed for cutting metal and have the grit anchored in a layer of resin. The resin holds the grit to the paper in a very strong bond. They last much longer than regular grade papers.  The abrasive is actually embedded in the resin, so while the film feels sort of smooth to the touch, as the resin wears away more, sharp, abrasive is exposed to the steel. All the films are 3mils thick (.003") and are not prone to tearing.

One of the most important things to bear in mind with "scary sharp" is that the paper must be fastened flat to a surface. Taping the edges down doesn't work - the paper bunches up in front of the cutting edge, making the paper prone to grabbing and ripping, and also potentially rounding the cutting edge - so this film has pressure sensitive adhesive (PSA) backed on the substrate. 

The very fine 0.3 micron aluminum oxide sheet is the equivalent of a 12000 grit waterstone.