It refers to any process that removes small (usually microscopic) particulate material, or removes very low concentrations of dissolved material from a fluid.
In example:
- Water polishing can be accomplished by removing "micro particles" in a normal filtration process.
- In chemical filtration fluid polishing can be achieved when eliminating magnetic resins from solutions.
- In spirits making the use of activated carbon will take out the rough edge usually associated with typical moonshine, and leave vodka's clean, tasteless & odorless, ready for flavoring.
- Polishing in beer brewing can also be considered fine filtration usually done before final filtration or in small breweries this can be considered the final filtration process.
- Fuel Polishing is defined as the removal of water, sediment, non-combustible particulate matter and microbial contamination below levels stated in ASTM D975 (Standard Specification for Diesel Fuel Oils) while resuspending combustible particulate matter to maintain ASTM standards for BTU value, lubricity, and cetane.