What Are Fortified Wines?

Fortified wines are regular grape wines that have been given an alcohol boost using grape spirits. While this does produce a high alcohol wine that isn’t the whole story and it isn’t why this practice began.

Port, one of the most popular fortified winesThe real reason fortified wines came into being was to solve stability issues in finished wine. Sherry is believed to be one of the earliest fortified wines which may have been produced as early as 1260 AD. Port came about a little later, during the 18th century.

Today we use sulfites and tight sealing closures to protect our wines. Back then the closures were not nearly so effective and they didn’t even know about all the tiny micro organisms we worry about today. Both of these factors would have made wine stability a much bigger deal.

Somehow though wine makers of old figured out that adding grape spirits to wines made it less susceptible to spoilage. We now know this stability comes from the increased alcohol content. Neither the yeast nor most spoilage organisms can withstand the alcohol.

The two most common fortified wines available commercially are Port and Sherry.

Port is fortified with aguardente vinica. A grape based drinking wine that is distilled to concentrate the alcohol to 35-60%. Sherry on the other hand is fortified with brandy, another grape distilled spirit.

To better understand what fortification is and what you can do with it lets explore each of these wines in turn.


Ports are generally made with red wines though not always. The aguardente vinica is added while the base wine is still fermenting in order to stop the fermentation.

The wine maker will taste the base wine as it ferments and when it reaches a desired level of sweetness she will add the aguardente vinica to stop the fermentation by raising the alcohol level beyond what the yeast has a tolerance for.

Because the base wine was still fermenting there is still sugar in the wine when it is fortified. This residual sugar is not consumed because the yeast die due to the alcohol level.

With alcohol levels of 18-20% Ports and other fortified wines are fairly stable against microbial spoilage in addition to yeast fermentation. They can still suffer from excessive oxygen exposure though.


Sherry is made a little differently than Port. First the base wine is allowed to ferment completely dry. Then brandy is added to increase the alcohol content of the wine. Some Sherry’s are back sweetened later on but they are first made dry.

The aging process of Sherry is also unique. Once finished the wine is aged in what’s called a solera system. This is a complex method of blending newer and older vintages. For more information on this really interesting aging method check out The Solera Wine Aging System.

How to Make Your Own Fortified Wine

It is entirely possible to make your own fortified wines using either the Port or Sherry method (with or without the solera). You can choose to use grapes or kits as your base wine.

According to The Winemaker’s Answer Book when working with a standard kit you can add less water to the grape juice concentrate so that the sugar is between 25-30%. Most kits (according to the book) have sugar levels between 22-24%.

When working with grapes you’ll want to ensure that you have sugar levels between 25-35 Brix. You may need to chaptalize your must to get sugar levels high enough.

Make sure you pick out a yeast with an alcohol tolerance upwards of 16% or so. Champagne yeasts tend to have high tolerances for alcohol.

When you add your alcohol will depend upon whether or not you’re making a sweet or dry fortified wine. If you want a sweet wine taste the it as it ferments and add your fortifying spirit when the sweetness is to your liking.

If you’re going for a dry fortified wine go ahead and make your base wine as you normally would (aside from adjusting sugar levels if you need to) and once it’s done fermenting add your grape spirit.

The amount of alcohol you need to add can be determined using the Pearson Square. In general Ports range in alcohol content from 19-23%.

After fortification proceed with clearing and bottling as you would with any other wine. Potassium sorbate will not be needed as the high alcohol levels will prevent further fermentation.

Delicious photograph by: liz west

  • Herb Yingling

    I have 2 gallons of very dry 1.5 year old Barbara grape wine about 14% ABV. The wine has never been above 45 degrees and there are no preservitives in the wine. Can I put it back in a carboy and add sugar to about 1.12 sg then add yeast and re-ferment until about 1.05 sg, rack,until clear then backsweenten to taste, will I have a fortified wine similar to a Port?

    • Hi Herb, great question. At 14% ABV it might be a challenge to get fermentation going again even if you do add a bit of sugar.

      If you did want to do this you would have to go with a yeast strain that has a high tolerance for alcohol, something like EC1118. What you’d need to do is add some sugar and treat the wine as if it were a stuck fermentation. That means creating a starter using a powerful yeast and rekindling fermentation that way.

      I wouldn’t add enough sugar to go all the way to 1.12. That amount of sugar definitely would not get fermented out even by a yeast with a high tolerance for alcohol. Also, a high sugar content and high alcohol content together could be quite prohibitive for yeast.

      One option would be to add some sugar, restart fermentation, then periodically add small amounts of sugar. Eventually fermentation will stop due to the alcohol level. Then you can add any additional sugar to sweeten it to your taste. It’s also a good idea to stabilize or filter the wine to prevent the yeast from getting started again later.

      Fortified wines, technically, are wines that have additional alcohol added to a finished wine in the form of brandy. If you want to make a port out of this wine, the easy way would be to pick up some brandy and start adding it until it tastes good to you. The additional alcohol will serve to stabilize the wine (this is how fortified wines came about in the beginning as well) as there aren’t many spoilage micro-organisms that can tolerate alcohol over 20% or so.

      I hope this helps Herb! Let us know what you decide to do and how it turns out.

      Cheers! -Matt