White Film on Wine: Film Yeast or Mold, and What to Do

A white film on top of wine is almost always film yeast: a thin skin of air-loving yeasts and bacteria that grows only where wine touches air. Remove the air and it cannot form. In a bottle, pour the wine out from under the film and smell it. In a carboy, top up until the film floats out, then raise the sulfite.

What Is the White Film on Top of My Wine?

A flat, matte, whitish-grey skin spread evenly over the surface is film yeast. Raised fuzzy spots are mold. Glassy grains on the bottom or the cork are tartrate crystals, and a dry white line on the glass above the wine is usually residue left as the level dropped.

What you see	Likely cause	Texture and colour	Smell	What to do
Thin flat skin over the whole surface	Film yeast (often with bacteria)	Matte, whitish-grey, may wrinkle	Bruised apple, flat, faintly sour	Pour or siphon the wine from under it, then smell
Thick rubbery disc	Vinegar mother (bacterial cellulose)	Grey-beige, slick, jelly-like	Sharp vinegar	Pour away, or keep it to start vinegar
Raised fuzzy spots	Mold	Furry; green, blue, black or white	Musty, damp	Throw the wine away
Clear or white grains on the bottom or cork	Tartrate crystals	Hard and glassy; they sink	None	Nothing: a natural salt of tartaric acid
Dry white ring above the wine line	Residue left as the level dropped, sometimes old film	Crusty, stuck to the glass	None of its own	Sanitise the neck, top up, watch the surface
Pale veil on a cask of sherry	Flor, grown on purpose	Creamy, waxy, even	Bread dough, salted almonds	Nothing: it is the style

Crystals stay where they fall and never spread across the surface; the guide to tartrate crystals in wine explains why cold whites throw them.

What Causes Film Yeast on Wine?

Film yeast grows when air sits above wine for days and wild yeasts and bacteria settle on the surface. They need oxygen, so a full, sealed container stops them. Low sulfite makes the surface easier to colonise, and so does a high pH, because sulfite works less well as pH rises.

Purdue University's extension sheet on film yeasts describes the skin as layers of several wild yeasts, including Brettanomyces and Candida. Acetic acid bacteria (the microbes that make vinegar) often grow alongside them. Purdue calls topping up the most important prevention, because these organisms depend on oxygen. It also notes that their off-aroma is often mistaken for the grape's own aroma.

The film usually appears after fermentation, once the carbon dioxide that kept air off the surface stops flowing. The yeasts turn alcohol into acetaldehyde, which smells of bruised apple. Their bacteria make vinegar, and some spoilage yeasts such as Pichia anomala make ethyl acetate, which smells of nail-polish remover. Those two smells are the core of volatile acidity in wine.

Quick check

One question on what you just read

You want to keep half a bottle for a few days with no white film. What works best?

ALeave the cork out so it can breatheBA small bottle filled to the top, sealed, coldCIts own half-empty bottle on the counter

Tap an answer to see how you did.

How Do You Fix White Film on Wine in a Carboy?

Get the film off the wine, then take away the air and lift the sulfite. Either top the carboy up with similar wine until the film floods out of the neck, or rack the wine from under the film into a clean, sanitised carboy. Fill the new one to the neck and fit a sound airlock.

1. Rack or flood. Keep the siphon tip well below the film and stop before the last few centimetres, or top up until the skin overflows.
2. Raise the free sulfite. Winemaker Magazine's advice for a filmed barrel is to keep sulfur dioxide at least 15 ppm higher than usual.
3. Measure the pH. Above about 3.60 sulfite works poorly, so the same advice adds about 0.5 g/L of tartaric acid, stirred in gently.
4. Check the seals. Purdue names the fluid inside the airlock as an often-neglected source of contamination. Refresh it and check that the bung seals tightly.

The free sulfite a wine needs climbs steeply with pH. Purdue's tables give the level that protects a wine at each reading.

Wine pH	Free SO2 at about 12% alcohol	Free SO2 at about 14% alcohol
3.0	13 mg/L	9 mg/L
3.2	20 mg/L	14 mg/L
3.4	32 mg/L	22 mg/L
3.6	50 mg/L	35 mg/L
3.8	79 mg/L	56 mg/L

If the pH reads 3.6 or above, lower it before adding more sulfite. Purdue warns that some film yeasts resist the recommended doses, so the headspace has to go as well. A batch caught early often survives: Winemaker Magazine's advice is that topping up and extra sulfite are enough if its taste and aroma are not damaged. Sulfites in wine explains what the additive does in the finished bottle.

How Do You Save Wine Under the Film in a Bottle?

Pour the wine out from under the film without breaking it, then smell a small glass. If it smells of vinegar or nail-polish remover, it has turned, so pour it away. If it smells only a little flat or of bruised apple, drink it today or put it in a stew. Breaking the skin mixes flakes into everything below.

1. Do not stir or shake the bottle. Move it gently to the counter.
2. Pour slowly from under the film, tilting the bottle so the wine leaves from the bottom of the neck and the skin stays behind.
3. Stop before the last few centimetres, because the film collapses as the level drops.
4. Smell the result in a clean glass, then taste a small sip.

The bruised-apple note is the one described in oxidized wine explained, and it gets stronger overnight. The guide to identifying wine faults by smell lists the other common off-notes, and wine flaws vs faults explains where "a bit tired" ends and "spoiled" begins.

How Do You Stop Film Yeast in an Opened Bottle?

Take the air away: keep wine in a full, sealed container and in the cold, so there is no surface for a film to grow on. If a bottle is less than half full and will not be finished tomorrow, move what is left into a smaller one.

• Downsize the container. Pour the rest into a small clean bottle filled to the neck.
• Seal it well. Use the screw cap, the cork pushed firmly back, or a tight stopper; how to reseal wine compares the options.
• Keep it cold. The fridge slows yeasts and bacteria as well as oxidation, for reds as much as whites.
• Drink it soon. A film needs days of air to show; how long wine lasts after opening gives the realistic window per style.

Vacuum pumps and inert-gas sprays reduce the oxygen in the gap, and wine preservation tools weighs them up. A smaller, full bottle costs less and works as well as most gadgets.

Is Film Yeast the Same as Flor in Sherry?

They are close cousins. Fino and Manzanilla sherry age under flor, a veil of yeast grown on purpose by leaving air in the cask and holding the alcohol in a narrow band. Accidental film yeast is an uncontrolled mix of spoilage yeasts and bacteria on a table wine.

Sherry casks are filled only about five-sixths full so the veil can form. Flor thrives while the wine stays between 14.5% and 16% alcohol. Above 16% it cannot survive, and the wine ages in contact with air as Oloroso, darker and nuttier. The veil shields the wine from oxygen, which keeps Fino pale, and it makes acetaldehyde, which with the yeast itself reads as salted almonds and bread dough.

If a sherry label says Fino or Manzanilla, the wine aged under flor; if it says Oloroso, it did not. The sherry wine guide walks through every style, and a similar yeast veil shapes vin jaune in the Jura. The line between an accident and a style is drawn in the wine fault vs style guide, and the rest of the faults live in our faults hub.

If a leftover white starts to smell like that Fino, finish it that day. The Sommy app has bite-sized courses, including Wine 101, that teach how to read a wine's smell step by step. Pour the last of any open bottle into a smaller bottle filled to the neck, seal it and put it in the fridge tonight.

Sources

1. Purdue Extension FS-51-W: Treatment of Film Yeasts (biofilm species, topping, airlock fluid, free SO2 by pH tables)
2. WineMaker Magazine, Wine Wizard: White film in my wine barrel (SO2, pH 3.60, tartaric acid, topping)
3. Wikipedia: Flor (alcohol range, cask filling, oxygen shield)
4. Wikipedia: Wine fault (acetaldehyde and ethyl acetate from film-forming microbes)
5. Wikipedia: Mother of vinegar (bacterial cellulose biofilm)