Often we receive calls from anxious, first-time winemakers wanting information on how to make their wines with more alcohol. Nothing wrong with that, if that's what they really want.
Driving up the alcohol in a wine is not all that difficult. With a little know-how you can achieve 15-16 percent, but you do have to know what you're doing. Going at it blindly can lead to problems in the form of a "stuck fermentation," resulting in a wine that's disgustingly sweet.
You can read more about how to properly produce a high alcohol wine by reading the article, "Making High Alcohol Wines".
While producing higher alcohol wines is do-able, the real question is, "Is that what you really want to do?" Having more alcohol in your wine comes at a price. Wines with higher alcohol can taste out of balance or "watery." This is because of the numbing effects that alcohol has on the tongue's taste buds. It diminishes the taste bud's ability to taste, giving the wine a watery impression. The result is a wine that has a lot of alcohol but little flavor.
Another issue that contributes to this problem is that with most high alcohol wines, the alcohol is driven up by adding more refined sugar than the recipe calls for, usually cane sugar. This sugar contributes no additional flavor qualities worth mentioning to the wine, but it will ferment and contribute to the wine's ending alcohol level.
With wines that have a normal alcohol level, 9 to 13 percent, a significant portion of the sugars are coming from the fruit. For example, wines that are produced from grapes grown in the wine regions of California, have no refined sugars added to them at all. All of the alcohol is being fermented from natural sugars that are contributed by the grapes themselves. This is what produces a wine of balance.
Most recipes you will find in wine making books that involve smaller berries such as blackberry, raspberry, strawberry and such, do not use 100 percent fruit to supply the sugars for fermentation. These smaller fruits are stronger in flavor than, for example, grapes.
These smaller berry wines do require some water and some sugar to dilute the stronger flavors of these smaller fruits. If not diluted, these fruits would produce a wine so strong and puckering in flavor that no one could possible drink them. It all comes down to a recipe that gives the wine a balanced flavor.
For one to increase the potential alcohol level of any of these balanced wine recipes by simply adding more sugar, is to take the wine out of balance--more tongue-numbing alcohol but no more flavor to compete.
What this all boils down to is, if you want to increase the alcohol level of a wine, you must do it in a way that keeps the wine balanced. If you are planning on raising the alcohol level of a recipe by adding more plain sugar, also plan on increasing the amount of fruit you use as well. Try to keep the ratio of fruit and sugar in tack, regardless of the size of the batch.
Here's an example. Suppose you have a 5 gallon wine recipe that calls for 20 pounds of fruit and 10 pounds of sugar. The rest of the volume is made up with water. After mixing all the home wine making ingredients together you discover by taking a hydrometer reading that there are enough total sugars in the must to produce a wine with 12 percent alcohol. What this means to you as someone wanting to increase the potential alcohol of the wine, is that for every additional pound of sugar you add to this recipe, you should also add 2 pounds of fruit to keep it in balance. More fruit flavor to compete with the additional numbing effects of the added alcohol.