3M Microfinishing Film

3M PSA adhesive backed Microfinishing Film is essentially a heavier duty version of imperial lapping film with a slightly thicker film backing and a harder compound of bonding resin. Microfinishing film is made with two types of mineral abrasive: Aluminium Oxide or Silicon Carbide.

Silicon carbide particles are longer, thinner, harder and more brittle than aluminium oxide, so they remove material very aggressively at first and then the finish becomes finer as the abrasive 'beds in'. Aluminium oxide is more like rocks than shards and delivers consistent sustained performance over time. My personal preference is AO for sharpening blades and SiC for precision lapping wood.

The high-strength polyester film backing is coated with premium, micron-graded mineral particles that are electrostatically oriented for greater cutting efficiency. The particles are bonded into a layer of resin that wears away slowly for increased durability.

PSA is the acronym for Pressure Sensitive Adhesive and is a heavy duty version of the adhesive on the back of a Post-It note, it is incredibly sticky stuff but relatively easy to remove with a few drops of orange oil.