Home winemaking mistakes: 7 beginner errors to avoid

In theory and in books, making your own wine isn’t that complicated. All you need is to find grapes, crush them, press them and then bottle. Yet anyone with a bit of winemaking experience will tell you about at least one time their wine turned to vinegar, turned out undrinkable or nearly did. And that’s when the disappointment hits its peak: so much energy goes into picking, destemming, crushing and pressing your grapes… only to find out you’ll have to wait until next year to try again. So I’ve gathered here seven mistakes that I either managed to avoid or made myself, to help maximize the chances of success of your next artisanal winemaking.

Settling for approximate cleanliness

It’s the first tip any winemaker will give you: always clean and sanitize all your equipment. Cleaning aims to remove particles, dust and any visible dirt, as opposed to sanitizing, which eliminates micro-organisms (bacteria, yeasts, etc.), making the equipment sterile. Cleaning can be done with regular dish soap, preferably unscented, whereas sanitizing has to use sulphited water (1 teaspoon per litre of water) or an oxygen-based sanitizer such as One Step.

Why is this so important? Because approximate cleanliness will encourage unwanted micro-organisms to show up in too-large numbers during alcoholic fermentation, such as acetic bacteria, Brettanomyces yeasts or lactic bacteria. Those are responsible for many wine flaws and can easily make a cuvée undrinkable. It’s hard to get rid of them in home winemaking other than with a sulphiting at 50 mg/L: better to try to prevent them at all costs.

Not measuring or noting anything

When a cuvée turns out well and tasting it with family and friends is a hit, the first reflex is to want to repeat the experience the following year. But for a cuvée to be reproducible, you have to remember how it was made and with what parameters. So I strongly advise writing a “technical sheet” for each cuvée covering:

• The Brix level (or Brix) of the grapes measured on picking day. Brix is the number of grams of sugar per 100 grams of liquid and is measured with a refractometer;
• The grape varieties used and the % of each in the case of co-maceration/co-fermentation; and
• The winemaking protocol, that is, the answers to the following questions: Were the bunches destemmed? How long did the skins macerate with the juice? What was the Brix of the juice before pressing? With what tool and with how much force was the pressing done? Was the maceration done at room temperature? What about alcoholic fermentation? How many rackings were done? How long was the wine aged and in what container?

This “technical sheet” will allow a degree of consistency from one year to the next for the same cuvée. Even better, it will let you experiment by varying one or more parameters in the future (e.g. skin maceration time) to improve your wine!

Not inspecting your wine regularly

I use the term “inspect” here because it’s not enough to smell or taste the wine: you have to do both, then take the opportunity to measure the gravity. A hydrometer then becomes essential. It’s especially critical to do this until alcoholic fermentation is finished and the wine has been fully pressed. Here is what a “regular” inspection consists of in artisanal winemaking, which you should note down on a sheet of paper each time:

• During maceration or fermentation: Every 2 days. Don’t forget to smell what’s coming off the fermentation vat in addition to smelling and then tasting the must itself. Indeed, if the vat gives off a slight smell of volatile acidity (nail polish) but the must doesn’t, there’s no cause for concern. Also, if the gravity has moved little or not at all since the last inspection, there is a fermentation problem;
• During aging: Every 2 weeks. It can be tempting to forget your wine until spring but that would be playing with fire. Even though fully fermented wine is much more stable, the small containers used in artisanal winemaking are prone to the appearance of a film of unwanted micro-organisms.
• During bottle aging: Every 6 months. The wine’s evolution will be much slower once in the bottle. A tasting every 6 months is then enough to determine whether its maturity is optimal. Be careful not to age it more than a few years, since most artisanal wines are mature after 6 to 12 months in the bottle and don’t lend themselves well to prolonged aging.

For regular inspections, the tool of choice is what’s called a “wine thief,” a kind of oversized pipette that makes it easy to draw wine from a carboy. I recommend this plastic model, which I’ve used for several years and which is easy to clean as well as unbreakable.

Leaving too much air in your vats and carboys

During fermentation, too large a volume of air can make it easier for acetic bacteria to appear. Even though it’s less common than during aging, you should still try not to leave more than 10% air in your vats during alcoholic fermentation. Be careful not to fill them too much, though! The must will expand and overflow from the heat the yeasts give off, as shown in the image below, captured during my 2025 harvest…

What’s more, as soon as alcoholic fermentation is complete, the wine in a carboy is no longer protected from oxygen. This is particularly dangerous during aging since, once again, it will encourage the appearance of acetic bacteria while causing premature phenolic oxidation of the wine. How can you tell if your wine is oxidized? Visually, it will have changed colour: if it’s white, it will have yellowed, and if it’s red, it will have taken on a brick-like hue. By taste, the fruit aromas, now nearly absent, may have been replaced by nutty, sherry or caramel aromas.

How to top up to minimize air in a carboy

Filling your carboys cleverly won’t fully prevent these ills, since wine evaporates naturally during aging. The various inspections will also, over time, bring the volume below what would be considered safe. At that point you have to “top up” your wine, which means adding wine up to a few centimetres from the bung (the rubbery part of an airlock). For a successful topping up, you also need to:

• Use wine from the same cuvée or, failing that, of similar quality and making;
• Make sure alcoholic and malolactic fermentations are complete; and
• Top up frequently, that is, every one or two months for a glass or plastic carboy, as opposed to an oak barrel where topping up is required every 2 weeks.

Not planning enough containers

It’s hard to plan exactly the right quantity of containers since the volume of the harvest will vary a lot throughout the winemaking, notably at the steps of:

• Destemming, where the volume taken up by whole grapes will drop by between 5% and 10% because the stems are removed. You’ll need to make sure here that the berries fill the container in which they’ll rest after crushing has taken place;
• Pressing, where the volume taken up by crushed grapes will drop by between 20% and 40% because the skins and seeds are removed. The wide variability is explained by the pressing technique: the more the juice is pressed, the smaller the losses, but at the expense of a more “muddy” and cloudy juice that needs to be clarified or racked; and
• Racking, where the volume taken up by the pressed juice will drop by between 1% and 5% depending on the thickness of the lees, since they will stay at the bottom of the carboy or vat.

In every case, a minimum of 25% of the initial volume will be lost and with a very light pressing, it could go as high as 50%. So 100 kg of whole grapes can yield anywhere between 50 L and 75 L of pressed juice. For example, if I only have 3 5 US gallon carboys (19 L each) and 70 L of juice is pressed, that means 13 L will be lost (70 L − 3 × 19 L)! It’s therefore essential to own a few carboys of every size to minimize your losses.

Bottling too quickly

Bottling has to be done at the right time, especially when making a pétillant naturel or a young wine with little aging in the “Beaujolais nouveau” style. Here are the main problems that can come up:

• The wine is bottled too early in its alcoholic fermentation: When making a pétillant naturel, the specific gravity should be between 1.000 and 1.006, ideally around 1.003, and not exceed 1.006. If the must is bottled above that value, the bottle could explode, particularly if it doesn’t have a reinforced base. Using a sparkling wine bottle isn’t desirable either, since the high pressure combined with the large amount of lees will very likely cause a geyser on opening.
• The wine is bottled before malolactic fermentation (MLF) has finished: MLF starts a few weeks to a few months after alcoholic fermentation ends. During it, lactic bacteria will release a little carbon dioxide and if the wine has been bottled, it will be very slightly effervescent, like a perlant or a “frizzante”-style wine. That produces very little pressure, but in the case of a bottle closed with a cork, it will be enough to push it out. To know whether MLF has taken place, watch the airlock, which will start and stop a second time. The tasting notes taken during inspections will also let you detect a certain roundness accompanied by a less lively acidity.
• The wine is bottled in the wrong bottle: It happens! It’s easy to mix up bottles for lightly sparkling wine with cider bottles. An easy rule for telling them apart is that cider bottles have a thick, reinforced base visible to the naked eye. Be careful too not to mix up the bottles requiring 29 mm crown caps with those requiring cork, particularly for clear bottles.

I’ve also consolidated in the table below the 3 families of pressure-bearing bottles. There are a multitude of suppliers today, making it impossible to provide an image representing every variety of a given type. My advice is therefore to weigh them, since the weight, which reflects the thickness of the glass, gives a good idea of its ability to withstand pressure.

Trying to make wine like the pros

Making wine in a glass or plastic carboy with little (under a year) or no aging (for a pétillant naturel) gives a distinctive and very interesting result while being easy to do in a home winemaking context. By varying the grape varieties, the length of skin contact with the juice, the presence or absence of stems and the intensity of the pressing, the possibilities are almost endless.

What’s less easy and much riskier? Aging your wine in an oak barrel, macerating the skins in the juice for more than 2 weeks, doing the traditional Champagne method, attempting aging under an oxidative veil… All these techniques are hard to master in a home winemaking context without significant experience in a vineyard or the guidance of an expert. What’s more, they carry a high risk of the wine oxidizing or turning to vinegar from the action of acetic bacteria.

By avoiding these mistakes, the worst will be avoided too!