Clarification is a step in the winemaking process that proceeds bottling. We clarify the wines to remove any suspended material created via naturally occurring chemical reactions during the winemaking process. They are insoluble and float around in the wine, creating a cloudy, dull appearance. On some occasions, the particles can change the flavour and aroma of the wine which we by no means want. Our wines should be crisp and clear when we bottle them. We use different methods to clarify our wines.
For the whites we usually just cool them down to let solid matter materialise and sink/precipitate to the bottom of the tank. They are then racked into a new tank and finally filtered very gently before bottling.
As most of our reds have spent some time in barrel, where they clarify naturally, little manipulation is needed besides a very soft filtration to ensure all left over yeast cells and also bacteria from the malolactic fermentation are taken out. However, we sometimes also use bentonite.
Bentonite is a 100% natural "impure clay" formed by the weathering of volcanic ash. It is an absorbent material that is able to bond with the floating particles that cause cloudiness in wine.
So how does it actually work?
This will get a little nerdy but it’s worth understanding. When hydrated in water the minerals in bentonite become negatively charged (i.e. ions).
The negative ions in the clay bond with positively charged particles floating around in the wine causing haziness. Generally wines are cloudy because the floating particles are all similarly charged (all positive or all negative).
Similarly charged particles don’t settle out because they resist each other like magnets of the same polarity. They need something with an opposite charge to bond with them so they’ll be neutral.
Because bentonite is negatively charged and dense when it does bond with a positively charged particle they both sink to the bottom of the tank. Once on the bottom we very simply rack our clear wine off of the sediment.