Chill filtered and un-chill filtered
Chill filtration is the process of removing and esters from whisky immediately after distilling. This is done for aesthetic reasons, as whiskies that haven’t been chill filtered can get cloudy when the whisky is chilled after bottling. This happens only in whiskies that are less that 46% ABV. Historically most major distilleries used chill filtration, but the process has grown out of favor over time as whisky connoisseurs prefer the taste of whiskies that haven’t gone through the process.
Technically this works by
cooling whiskies down to between C−10 and 4 °C (14 and 39 °F), often roughly 0 °C (32 °F). At these low temperatures, the solids freeze, and are easy to extract. Following removal, distilleries barrel the whisky.