Winemaking in Action: Tanks and Fermentation!

We’re back with part 2 of our Winemaking in Action Series! Hopefully, after last week you are all experts on sorting, crushing and pressing. If you missed part 1, read here! This week we are diving deeper --- let's chat tanks and fermentation!

Basic Terms to Know

Winemaking: Winemaking is the production of wine, starting with the selection of the fruit, its fermentation into alcohol, and the bottling of the finished liquid.

Tanks:  Vessel where fermentation takes place.

Fermentation: The process by which grape transforms into wine. During fermentation, yeast converts grape sugars into alcohol.

Cap: The mass of solid matter that rises to the surface during fermentation. 

Pump Over: Process by which  fermenting juice is circulated, or pumped, over the cap.

Punch Down:  Process by which  a device pushes the cap down, breaks it up and submerges it again.

Must: Crushed fruit and skin.

Lees: The dead leftover yeast cells from the fermentation process.

Glycol Jacket: Temperature regulation technology that archives cooling from the exterior.


At this point in the winemaking process, winemakers have several options to choose from to decide which type of tank they would like to ferment their wine in. The tank is an important step in the winemaking process, it is where fermentation takes place. 

Stainless steel tanks are an option many winemakers choose to use. They are among the most common of tanks, and offer many benefits including temperature regulation and easy cleaning! Tanks can be placed indoors or outside depending on the climate and region of the winery. In most tanks there is a layer of insulated foam to help protect against heat. Underneath the foam or outer layer is an additional double wall of insulation that is refrigerated, which helps regulate the temperature of the wine inside the tank. For tanks placed outdoors, oftentimes they will have a glycol jacket, which is a temperature regulation technology that archives cooling from the exterior. 

While stainless steel tanks are among the most popular tanks, wood tanks, concrete tanks, and amphorae are other types that may be used by the winemaker. 


Fermentation is the next step  in the winemaking process in which grape must (crushed grapes and skin) transforms into wine. During this process, yeast converts grape sugars into alcohol. The fermentation process for whites and reds vary.

White Wine Fermentation

  • White wine fermentation usually happens directly after pressing. 
  • The juice from the pressing process goes into the tank to settle, its’ chilled, and the solids start to settle in the bottom.
  • Fermentation begins by adding yeast and is controlled through refrigeration - this process can take about 2-4 weeks.
  • Once “done” it's’ time to stir the lees, which are little dead yeast bits that are at the bottom of the tank. The lees float up in the wine and add flavor and texture to the wine.

Red Wine Fermentation

  • Red wine fermentation happens with grape skins and juice combined usually prior to pressing. 
  • The grape skin contact in red wine production gives the color, flavor and texture that is integrated into the juice.
  • Fermentation begins by adding yeast and is controlled through refrigeration - this process can take about 1-2 weeks.
  • After the yeast is added, the cap starts to form atop the tank, these need to be blended back into the tank which happens by way of pumping over or punching down. 
  • A pump over circulates the fermenting juice over the layer at the top of the tank. A punch down is when a device pushes the top layer down, breaks it up and submerges it again.
  • After fermentation the converted liquid is transferred into a wine press, to separate the skins and seeds from the wine.

As mentioned, the fermentation process varies for reds and whites. This process can also be different dependent on the winemaker and their specific preferences. The wonderful thing about winemaking -- no two winemakers or wineries are the same, which is why we get some many delicious and unique varieties of wine!

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