Bentonite is a common addition to winemaking used to clarify wines and is generally used only for white wines. It removes any protein haze and can also be utilized to fine any ‘off’ aromas.
What is Bentonite & How Does It Help Wine?
The use of bentonite is usually needed for white wines first, before the fermentation has been started. You will need to make a ‘slurry’ of bentonite to add it to wine, much like you make a slurry out of flour and water before you add it to any sauce in cooking to thicken it.
However, in this case, we are not trying to thicken the wine. The bentonite is impure clay created by weathered volcanic ash. The material is very absorbent and it binds and bonds onto any floating particulates which cause haziness or cloudiness in wine. Once it binds to these particles, it will eventually fall out of the wine helping improve its overall clarity.
Two Types of Bentonite
There are two types of bentonite used for fining wine; sodium and calcium. They both contain different minerals, which will probably be listed on the package. However, none of these minerals will actually be ‘added’ to the wine. The purpose of adding any fining agent is to have it bind on these clouding proteins and eventually precipitate out of the wine to the base of your fermentation container. They are easily removed by racking the wine and syphoning the wine from the surface ever so carefully so as to leave the solids behind.
If you utilize sodium bentonite, you will mix it with water and gradually add it to the wine, but once it is mixed into a solution, the sodium in the form of salts are left behind. As for calcium bentonite, it leaves behind calcium. This is preferred to salt, however, you have to be careful how much you add as you could later be dealing with tartrate instabilities (other solids which precipitate out of wine as salts), but most are harmless.
4 Steps to Using Bentonite Properly
You must utilize the bentonite properly or it will not clarify your wine at all. Here is what you do:
1. You want to rehydrate the bentonite powder by mixing vigorously every 2 teaspoons per ½ cup of water around 140°F(6°C). If the water is not warm enough, it will clump and fall to the bottom of the container. Mix it well for a long time until you can dip your hand in it and it just appears and feels smooth with everything dissolved. For small batches, you can just use a common kitchen whisk. For larger operations, they actually use a long wand attached to a drill bit with a propeller and place it in the container with the drill running to mix it well. Some people will tell you to let it sit for 24 hours before use so that it is fully hydrated, but that is not necessary.
2. Add your slurry to the wine at a ratio of one to two tablespoons per gallon. One being for mild haze and two for thicker.
3. Stir the mixture slowly into the wine, but try not to do so by mixing in too much oxygen. A line with a gas line while you do this can help.
4. From here, you can let your juice or wine rest for about 4 days more or less until the wine/juice is clear. From this point on, you can rack your juice/wine from the solids and go on with the next step in your process.