“Clarity is the most important thing. I can compare clarity to pruning in gardening. You know, you need to be clear. If you are not clear, nothing is going to happen.”
—Diane von Furstenberg
Fining is the addition of an adsorptive or reactive substance to reduce or remove one or more components in a wine. Fining agents improve clarity, color, flavor, and stability in a finished wine.
Fining kits is different from grapes and/or commercial wines: Kits are designed to go from pitching yeast to bottling in less than eight weeks. Grape wines often get more than a year in processing and élevage (maturing) before they are bottled. This compression of the winemaking schedule demands a rigorous fining regime. Without effective fining the wine won’t clear in time for bottling.
Interestingly, the simplest way to achieve more rigorous fining (using lots of very strong fining agents) isn’t the method kit manufacturers choose. There are fining agents available that can strip all suspended material out of wine in only a few hours. The trouble is, the efficiency of a fining agent is directly related to how much good stuff it will strip out of the wine along with the cloudy material, and how many traces of itself it leaves in the wine.
I recall a demonstration that a supplier did for me once using a cyanoacrylate-based agent normally used on unfermented juice. Stirred into suspension it immediately coagulated out in the wine in large flakes. By the time the stirring paddle was out of the carboy it looked like a snow globe. Forty seconds later the wine was crystal clear — so clear in fact that it looked as though it had been fine filtered. Unfortunately, it had lightened the Syrah wine into a medium-rosé color and left it with a smell much like a tire fire in a plastics shop. While the clarity and speed of fining were ideal, the result certainly wasn’t!
The compressed production schedule isn’t the only factor that governs how fining gets done. In grape winemaking fining has a small amount of trial-and-error. In commercial winemaking they do bench trials, testing batches of wine with various fining agents to determine the best aesthetic result, typically looking for the fining that clears the wine while minimizing any flavor and aroma impacts. Grape winemakers will also use tools and technology with their fining regimes, adding finings with pumps that whirlpool the wine, turning on chilling jackets and crashing the must to nearly freezing, etc.
Making wine at home with grapes can be similarly ad hoc. Home grape users may or may not do bench trials, but the standard is to use a familiar, reliable agent, such as bentonite and perhaps gelatin or egg white, and then wait to judge the results. If it does not clear, another fining is used, or the temperature of the wine is changed (typically lowered, as in commercial wines) to increase precipitation rate.
Wine kits are billed as complete solutions for the home user. The manufacturers guarantee they’ll clear on time and be ready for bottling on the schedule outlined in the instructions, so the finings have to work the first time, and on every kit, which is a pretty bold goal. As one commercial winemaker contemplating making wine in 6-gallon (23 L) batches said, “I don’t know how any of you do it. When I make wine in less than 10,000 liters I screw it up!” That’s because the initial starting conditions for a kit influence so many of the downstream characteristics of the wine that it’s difficult to control all of the variables well enough to ensure finings work consistently. That’s why wine kits typically employ a five-stage strategy that starts even before the yeast gets pitched into the juice. Each of the stages supports the others, and they have to be done in sequence to achieve full clarity. Those stages are:
Start — The juice has the fining agent bentonite added to it, and has to be in a specific (high) temperature range before yeast pitching.
Stir — After fermentation is complete, the wine is stirred very hard to disperse gas.
Smash — Yeast are stunned by a sulfite addition.
Sweep — A combination of fining agents clears the wine.
Suppress — Potassium sorbate additions prevent any remaining yeast in the wine from reproducing.
There’s no getting around it: Adding bentonite to juice that’s not only already absolutely clear, but also hasn’t even fermented yet, seems like a pretty dumb idea. After all, what good can it do when there’s nothing for it to work on?
That answer is two-fold. First, the clarity of the juice works against it. Yeast prefer to bud off blebs (daughter cells) while attached to a surface. Clear juice affords few of these, but the very tiny particles of bentonite are ideal for it. The extra surface area decreases the time lag between yeast pitching and the start of fermentation, which is a win because the faster the wine begins fermenting, the sooner it will produce carbon dioxide gas, and the sooner it can finish making that gas — gas in suspension churns the wine, making fining ineffective.
That’s also why wine kits are typically fermented between 72–77 °F (22–25 °C). Not only do warmer fermentations start faster and finish sooner, warm liquids retain less CO2 (think of cold Champagne versus hot Champagne — fizzy and zesty versus flat and foamy) so they degas much more easily, which brings us to . . .
With active yeast fermentation usually taking less than four weeks, the wine doesn’t have the time that a commercial wine or a grape wine usually gets before the instructions tell you to degas and fine it. This means there’s a lot of CO2 still present at fining and stabilizing, and it’s why the instructions tell you to “stir vigorously” for a variety of times, and sessions, often three times for two minutes a session — if you don’t stir hard enough the finings won’t work because the bubbles coming out of solution will “churn” the finings and the particles back into suspension as they float to the top.
That much stirring is very taxing if you’re doing it with enough vigor to chase bubbles out of the wine. It’s not stirring as much as it is “beating like heck.” The best way to stir hard enough is to get one of the drill-mounted stirring whips available at your local home winemaking shop. There are several models, but the Rolls-Royce of the category is a three-prong job that’s full reversible and brilliantly overbuilt. Once the wine is degassed it is time to . . .
Once the wine is finished fermenting and free of CO2, it’s time to knock the yeast down so they get out of your way. A sulfite addition of between 20 and 50 ppm FSO2 will do the job. Once the yeast get used to a diminished life, it’s time to oppress them even further, or should I say . . .
Fining agents glom onto particles in the wine and pull them out of suspension. Gelatin and isinglass are positively charged and form a hydrogen bond to phenols (such as the tannins in red wine). Isinglass is much gentler than gelatine.
Bentonite is a naturally-occurring, negatively-charged clay that 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.
Kieselsol, kind of like liquefied sand, is another negatively-charged agent that binds well to proteins. It’s often used in conjunction with isinglass or gelatin, and is especially effective in white wines where it replaces the tannins that reds would normally have.
The finings will pull most of the yeast out of suspension, leaving the wine fairly clear, and the yeast population at a low level, incapable of continuing fermentation, leading to greater stability.
When the yeast are reduced, it’s time to . . .
Potassium sorbate has a specific function in kit winemaking. It doesn’t prevent oxidation, and it doesn’t kill any kind of yeast or bacteria. What it does is suppress yeast breeding. Without filtration, young wine, even if it’s fined and sulfited, can have billions of live yeast. Sorbate acts as a kind of birth control, so when these yeast die there are no new ones to replace them, rendering the wine much more stable.
An important note for first-time winemakers: Because sorbate doesn’t work well on all types of bacteria you have to use it in conjunction with sulfite. In particular, lactic acid bacteria not only isn’t harmed by sorbate, it treats it like a delicious foodstuff, converting part of it into a compound called hexadienol, sometimes called “geraniol” because it smells like rotting geraniums. Lactic acid bacteria is easily suppressed by even moderate sulfite levels — always sulfite your wine.
Once the five S’s are complete, the wine should be perfect: The color should be stable, it should be clear enough to read a newspaper through (if it’s a white wine!) and it should be microbiologically stable. Done right, fining accomplishes all of these things while preserving the desirable flavors and aromas. Follow your instructions and your wine will be just fine!