Bentonite clay

An astute winemaker contacted me with a very pertinent question.
Tim,
I did the Master Vintner Pinot Noir yesterday and was kind of surprised that there was no Bentonite. I thought that you had thought this was a good thing in kit winemaking. If not needed, please let me know.
Robb H
Robb,
Excellent catch, sir. Yes, the kits I worked with previously had an addition of the fining agent, Bentonite, on day one. It's a common technique, done for a few reasons. But before we explore those, let's look at what Bentonite is.

It's particularly good at binding to unstable colloidal material and proteins, pulling them out of suspension. A colloid is a mixture in which one substance of microscopically dispersed insoluble particles is suspended throughout another substance. To understand this, picture your wine as a solution of all kinds of goo from the inside of a grape. There's sugars, tannins, flavor and aroma compounds and a lot of gums, pectins, proteins and colloids. These float around with a weakly positive electrical charge on them, kind of like what happens when you walk across a carpet in sock feet and get a static shock when your touch the light switch.

Since the juices used in some kits are not completely protein stable they need to be hit with a strong fining agent like Bentonite to keep them from being cloudy after fermentation. The easiest way to get it in was to put it in on day one and leaving it in until primary fermentation is over. There's also a small benefit to yeast health, as the particles of Bentonite act as anchor points for yeast cells to bud from, helping ensure a quick start to fermentation.

So there you have it: Robb, you successfully demonstrated Vandergrift's First Precept of Home Winemaking (Read The Instructions!) and seem willing to follow the second (Follow the Directions, Omitting No Detail However Small, Making No Change, However Slight)--good job! If you're as much of a Pinot Noir fan as I am, you're going to love your wine.