How to Make Homemade Wine Stronger

Homemade wine gets its alcohol from one place: the sugar the yeast ferments. To make it stronger you raise the sugar in the must before fermentation, choose a yeast that can keep working at the alcohol level you are aiming for, and give that yeast enough nutrient to finish the job. Measure every step with a hydrometer, so you know the strength instead of guessing it.

There is a ceiling. The strongest wine yeasts sold for home use are rated by their maker at up to 18% alcohol. Anything stronger than that is a fortified wine, which gets its extra strength from added distilled spirit rather than from fermentation.

How Strong Can Homemade Wine Be?

The yeast decides. As alcohol builds up, it becomes toxic to the yeast, and each strain stops at a different point. These are the alcohol tolerances the makers publish for common wine yeasts:

A tolerance is the most the yeast can reach under good conditions, not a promise. Cold cellars, a lack of nutrient or a very sugary start can stop a ferment well short of it. Our guide to wine yeasts covers which strain suits which wine.

Where the Alcohol Comes From

Yeast turns the sugar in the must into alcohol and carbon dioxide, so the sugar you start with sets the most alcohol you can get. A hydrometer measures that sugar as specific gravity (SG). The usual home formula multiplies the drop in gravity by 131.25, and our wine ABV calculator does the math for you.

Here is what the formula gives for different starting gravities, assuming the wine ferments all the way down to 1.000:

Dry wines often finish slightly below 1.000, which adds a little more. Match the starting gravity to the yeast: a 71B yeast rated at 14% in a must that starts at 1.120 will usually stop early and leave the wine sweet.

Step 1: Add Sugar Before Fermentation

Adding sugar to juice or must to raise the final alcohol has a name: chaptalization. WineMaker magazine’s guide to chaptalization gives a simple rule for grape juice: about 10 grams of sugar per liter raises the reading by 1° Brix. Its example takes 25 liters of juice from 18 to 22° Brix with 1 kilogram (2.2 lb) of sugar, and it notes that 22° Brix leads to a wine of around 12% alcohol.

The same guide suggests 25° Brix as the most a beginner to intermediate winemaker should aim for, because stuck fermentations become more likely above it. Our sugar calculator works out the amount for your batch from two hydrometer readings.

Dissolve the sugar in some of the warm juice before adding it, stir it through the whole batch, and take a fresh reading once it is mixed in.

Step 2: Pick a Yeast That Can Get There

Once you know your starting gravity, choose a yeast with room to spare. For wines aimed at 14% or more, EC-1118 and K1-V1116 are the usual choices because both are rated at up to 18%. EC-1118’s listing also gives a wide fermentation range of 50 to 86°F.

Higher tolerance is not always better. A strain like 71B is chosen for fruity aromas, and a softer wine of 12 to 13% often tastes better than a hot, thin one at 16%. Decide the style first, then the yeast.

Step 3: Feed the Yeast

A strong wine asks a lot of the yeast. North Dakota State University Extension’s Getting Started With Home Winemaking explains that yeast nutrient promotes a rapid start to fermentation, and that a lack of it can stress the yeast and give the wine a rotten egg smell. Its fruit wine recipes use 1 teaspoon of yeast nutrient per gallon, the same rate printed on the Fermax nutrient listing.

More is not better here either. Purdue University’s enology fact sheet on film yeasts warns that excess nutrient left over after fermentation feeds spoilage organisms, so follow the recipe or the label rather than doubling up.

Step 4: Consider Adding Sugar in Stages

Sugar does not have to go in all at once. WineMaker’s chaptalization guide points out that there is no reason a wine cannot be chaptalized later in the process. Adding part of the sugar at the start and the rest once fermentation is well under way means the yeast never faces the full sugar load at once, which can help it reach a higher alcohol level. Take a hydrometer reading before and after every addition and keep a log, or you lose track of the strength.

Step 5: Measure, Do Not Guess

Take a reading before the yeast goes in and another once the gravity has held steady for several days. Plug both into the ABV calculator. If the gravity stops well above 1.000 and stays there, the yeast has given up early; our guide to stuck fermentation covers how to get it going again.

What About Fortified Wine?

Port and other fortified wines get their strength from distilled spirit added to the wine, not from fermentation. The Alcohol and Tobacco Tax and Trade Bureau is clear that while adults may make wine and beer at home for personal or family use, federal law strictly prohibits producing distilled spirits at home. Do not try to concentrate homemade wine by distilling or freezing it.

The Legal Side

Federal rules allow home winemaking for personal and family use without a permit. Under 27 CFR 24.75, NDSU Extension summarizes the limits as 100 gallons a year in a one-adult household and 200 gallons where two or more adults live. The strength of the wine does not change those limits, but home wine may not be sold, and state and local rules can add their own conditions.