Q: I read in a wine book that the sulfite residue from sulfite sterilizing solution used to clean bottles provides adequate sulfite. Some members of my home winemaking club, Cellarmasters, add no sulfite. Others add a precise measurement based on pH. What do you suggest?
— Don Harris • Thousand Oaks, Calif.

A: To sulfite or not to sulfite: That is the question. It’s one that fires hot debates in the cellars of wineries worldwide. Sometimes seen as a personal choice, the use of sulfites in winemaking requires a delicate sense of balance and a light (though judicious) hand. Otherwise, your wine can be irreparably ruined.

Sulfites serve several purposes in winemaking. They provide antimicrobial, antibrowning, and antioxidant activities in musts, juices, and wines. Naturally, since winemaking is not a sterile process (and there are always the droves of spoilage organisms waiting for a chance to get in on the action), it’s important to keep this in mind when making decisions about how much sulfite to add and when.

Sulfites added at bottling are intended to further protect the wine once you have no more control over it. A high enough sulfite level — most winemakers will say about 40 parts per million (milligrams per liter) — will retard the growth of most microorganisms in the bottle that could cause off odors, unsightly precipitates, or even secondary fermentation. However, be aware that each batch of wine is different and that winemakers must rely on their experience in addition to hard numbers. 40 ppm may not get the job done, especially if you don’t practice stringent sanitation or use especially moldy or damaged fruit.

It is usually a good idea to use a tool such as the commercially available Sulfikit to measure the sulfur dioxide in your wine and then to calculate how much more you need to add at bottling to stay within a reasonable level. Much sulfur dioxide gets bound up in the wine during the fermentation and racking processes and thus becomes unavailable to the solution as an antimicrobial agent when it comes time to bottle. So it makes sense that 40 ppm added at the crusher will not result in 40 ppm before bottling — and you’d have to swirl your bottles with a pretty potent sulfur dioxide solution to get the desired amount into the finished product.

My recommendation: Measure the amount of sulfite you have, then do the math and meter a sulfur dioxide solution of the appropriate concentration into your bottles before filling them with wine. Even many commercial winemakers have to play this one by ear and aren’t any better equipped to do it than you are.

The Wine Wizard is an expert on home winemaking whose identity, like the identity of all superheroes, must be carefully guarded. Send in your question to the wizard at wiz@winemakermag.com.