Ask Wine Wizard

Understanding Bentonite


Richard Parry — Ignacio, Colorado asks,

In your great book The WineMaker’s Answer Book you say, “Small scale winemakers are probably safe adding 3 grams per gallon (4 L) of bentonite to their wines.” Are you referring to sodium bentonite or to calcium bentonite? Would you please explain the differences in the two bentonite options relating to dosages and effectiveness?

Wine, as I’ve often written, is a complex chimerical soup. Wine naturally contains lots of different amino acids and some of those amino acids are in long-chain form and actually are proteins. Because proteins are pretty big molecules (as molecules go), they sometimes are so big they can’t be dissolved in the wine as a liquid anymore and are actually visible to the naked eye. If your wine has enough of these proteins your wine might be so cloudy as to have a visible “protein haze.” Now, amino acids and proteins in wine aren’t dangerous or bad for you, but they might keep your wine from being the sparklingly clear liquid you’d like it to be. This is where fining (or treating) with bentonite comes in. Bentonite is a naturally-occurring clay that has been used in winemaking for centuries. It comes in powdered form and is rehydrated in water or wine before being added as a slurry to wine. The clay particles swell up in the liquid and adsorb the positively-charged protein molecules. Then the big protein-bentonite agglomeration gets so
Response by Alison Crowe.