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Fermentation FAQ

Fermentation Questions

I pitched my liquid yeast and nothing is happening . . . / What is a lag time?
What will affect lag times?
What can I do to reduce lag times?
I forgot to refrigerate my liquid yeast, and it’s been out of the fridge for _______ hours/days/weeks; should I pitch it anyway or buy new?
Should I aerate my wort? / What is aeration? / What is the difference between aeration and oxidation?
Should I attach a blow-off tube during primary fermentation? / What is a blow-off tube?
When should I transfer my beer to a secondary fermenter?
How long should my beer condition for? / How long does my beer need to be in a secondary fermenter for?
What is Irish moss? / How do I use Irish moss?
My airlock stopped bubbling, is my beer finished fermenting? When is my beer ready to bottle or keg?
Should I strain my wort before putting it in my fermenter?
My beer is cloudy and/or full of chunks in my fermenter, is this normal?
What is yeast nutrient? / Do I need to use yeast nutrient?
What is the difference between yeast nutrient and yeast energizer?
What is dry hopping?
What temperature should I ferment at?
What’s the difference between ale and lager yeast?
What is a pitch rate?

I pitched my liquid yeast and nothing is happening . . . / What is a lag time?

Don’t worry, you’re experiencing what is known as a ‘lag time.’ This is where yeast cells are propagating (or multiplying) in order to reach an adequate amount to ferment your beer. Lag times can be as much as 72 hours, so if it’s been a couple of days and there’s still no activity, be patient. It only takes a single cell of yeast to produce enough cells to ferment. It will simply take longer.

What will affect lag times?

1. Insufficient aeration: During propagation, yeast needs oxygen to build new cell walls. Without adequate oxygen, cell count is low and yeast is unhealthy and may produce off flavors.
2. Insufficient pitch rate: This refers to the amount of viable yeast that you pitch into your wort. When cell counts are low, you will experience a longer lag time as the yeast will need to propagate.
3. Temperature: If you pitch your yeast when your wort is either too hot or too cold, you may experience a longer lag time while the yeast adjusts to unfavorable conditions.
4. Gravity: High gravity (high sugar) worts take a higher pitch rate, more aeration and more nutrients in order to achieve a healthy fermentation. Yeast starters are a great way to ensure adequate pitch rates and yeast viability.
5. Yeast strains: There are many yeast strains available to homebrewers, and some simply take longer to get going.

What can I do to reduce lag times?

1. Aerate wort: Whether this means shaking your carboy for 20 minutes, utilizing a pump (a simple fish tank pump works great), or investing in an oxygenation system to force pure oxygen into your wort, proper aeration is key to having a healthy, active fermentation. While it is possible to over-oxygenate wort, it is only a serious risk using pure oxygen.
2. Make a yeast starter: A yeast starter is the best way to ensure healthy fermentations, especially for high gravity wort. See “Making a Yeast Starter.”

I forgot to refrigerate my liquid yeast, and it’s been out of the fridge for _______ hours/days/weeks; should I pitch it anyway or buy new?

Liquid yeast should stay refrigerated until a few hours before it is pitched (added) into wort. The goal is to activate the yeast from dormancy by bringing it to fermentation temperatures before pitching it into the wort. This will reduce unnecessary stress incurred by the yeast from rapidly changing conditions (both temperature and the presence of fermentable sugars).
Generally, the longer liquid yeast is left at higher temperatures the more viable yeast begins to die because of lack of oxygen and lack of energy (food and nutrients). While forgetting to refrigerate yeast for 24-48 hours is not a huge concern, just remember that healthier yeast cultures will lead to better fermentations and result in better tasting beer.
However, it only takes a single cell of yeast to produce enough yeast to ferment a batch of beer, though it is best to make a starter before fermentation begins to ensure an adequate pitch rate. If the yeast has been out of refrigeration for over 72 hours (3 days), or in direct sunlight for considerable time, there is a serious risk for poor fermentations and off-flavors without properly culturing the yeast, so one should either replace the yeast or make a starter.

Should I aerate my wort? / What is aeration? / What is the difference between aeration and oxidation?

Aeration is the process of dissolving oxygen into unfermented wort for the yeast to utilize during propagation/respiration. This is an aerobic process (requiring oxygen) where yeast cells are building new cell walls and increasing their population in order to ferment. Without proper aeration fermentations can be slow, have a long lag time, estery, and low attenuating. Aeration is critical to ensure a healthy fermentation and great tasting beer.
However, there is a difference between aeration, which occurs before fermentation, and oxidation, which is when oxygen is introduced after fermentation has begun. Whereas aeration is necessary, oxidation should be avoided as it leads to premature staling and can make beer taste like wet cardboard. Oxidation can occur from splashing beer around during transfers between fermenters or to the bottling bucket. Many brewers also believe that oxygen being introduced into wort above 120°F can lead to oxidation during storage, so it is best to only aerate cool wort. It should be noted that it is more difficult to dissolve oxygen into high gravity beers, so the aeration/oxygenation time should be increased to promote better fermentations.

Should I attach a blow-off tube during primary fermentation? / What is a blow-off tube?

Primary fermentation can be very active, even explosive, to witness. Yeast churns and swirls in the fermenter creating not only heat but also pressure due to CO2 production. This CO2 needs to be released using an airlock if the fermenter is large enough to prevent the krausen (foam due to CO2 escaping solution) from coming out; 6½ gallon glass carboys usually have adequate head space to keep krausen inside. If using a smaller fermenter, simply attach a clean and sanitized length of ¼” tubing to a bored stopper or use 1” tubing inserted directly into the neck of the carboy and run the tubing into a jar/bucket/pot of water or sanitizer. This way, should there be enough krausen to escape the carboy, it will flow into the catchment instead of filling the airlock, or worse, by blowing off the rubber stopper or lid and covering the walls and floor with wort.

How do I know fermentation is complete? / When is fermentation complete?

When fermentation is finished can vary based on the the type of beer and yeast, among many other things. As a general rule, fermentation is considered finished if the beer is within the target range for Finished Gravity, and your hydrometer readings have been the same for multiple days.

When should I transfer my beer to a secondary fermenter?

As primary fermentation nears completion yeast activity slows, krausen will recede into the beer, and after a few days yeast will begin to flocculate (drop out of solution). During this interim stage, viable yeast will begin to consume and reprocess off-flavors naturally produced during fermentation. If there isn’t an adequate amount of yeast, then off-flavors will be more noticeable in the finished beer.
The best way to determine when to transfer from a primary to a secondary fermenter is when the yeast begins to flocculate. You will notice that the beer will remain cloudy even after krausen has receded, but when a thin layer of translucent beer forms at the top and begins to expand downward in the fermenter, it is ready to transfer.

How long should my beer condition for? / How long does my beer need to be in a secondary fermenter for?

There are two main reasons for using a secondary fermenter: to allow the beer to condition/mature/age and to expedite and encourage yeast to drop out of solution (flocculate). Therefore, once the beer is clear and at the target gravity, it is ready to be carbonated and packaged.
However, with some caveats, the longer a beer is aged the smoother and better it will taste. Most homebrewers discover this when they drink the last couple of bottles from a batch that taste better than previous bottles. This is simply because the beer has had longer to mature allowing flavors to round out and results in a better tasting beer. There is an argument regarding bulk aging (in a fermenter or carboy) versus bottle conditioning and whether beer should be aged ready to serve (read: carbonated), but it really depends on the style of beer (including traditional methods, ingredients and/or yeast strains), the particular fermentation, and the gravity of wort. A high alcohol spiced beer will need to be aged much longer than a lower gravity IPA that has been dry hopped for example.

What is Irish moss? / How do I use Irish moss?

Irish moss is commonly used as a clarifier for beer, specifically as a protein coagulant. It is derived from a particular red seaweed (referred to as carragheen) and as negatively charged plant material, it will bond to positively charged proteins in the brew kettle and aid in sedimentation.
Depending on the recipe, ½ to 1 tsp. of Irish moss for five gallons of beer is all that is needed. Simply re-hydrate by placing in a glass of warm water and add the solution to the brew kettle when there is 10-15 minutes left in the boil.

My airlock stopped bubbling, is my beer finished fermenting?
When is my beer ready to bottle or keg?

As primary fermentation nears completion yeast activity slows, krausen will recede into the beer, and after a few days yeast will begin to flocculate (drop out of solution). During this interim stage, viable yeast will begin to consume and reprocess off-flavors naturally produced during fermentation. If there isn’t an adequate amount of yeast, then off-flavors will be more noticeable in the finished beer.
So even though the airlock has slowed down or even stopped, there may still be active yeast fermenting and consuming off-flavors. The best way to determine when your beer is finished fermenting is when it has reached your target gravity and stabilized over a couple of days. In other words, follow your hydrometer and you can’t go wrong.

Should I strain my wort before putting it in my fermenter?

Absolutely. When fermentation begins, there should nothing but wort and yeast in your fermenter. Besides contributing to off-flavors, leaving boiled hops and/or grain in the wort can clog the blow-off tube (if using ¼” tubing).

My beer is cloudy and/or full of chunks in my fermenter, is this normal?

Yes. During an active primary fermentation, yeast will be a torrent inside the fermenter, rising, falling, swirling, sometimes you can even see them do a special dance in a vain attempt to communicate with you, their caretaker (not really, but it is fascinating to watch the constant storm inside your fermenter).

What is yeast nutrient? / Do I need to use yeast nutrient?

Yeast nutrient is recommended when brewing mead, wines (especially fruit or country wine), or beers with a high amount of sugar adjuncts in them (including honey, fruit, or other sugars). While there is usually plenty of nutrients available in all-grain and all-malt derived extracts, other sources of fermentable sugars are lacking in the nutrients necessary for healthy cell growth and fermentation.
Yeast nutrient is commonly a mixture of diammonium phosphate, yeast hulls, biotin, vitamins, and minerals that increase the overall health of the yeast and thus lead to better fermentations.

What is the difference between yeast nutrient and yeast energizer?

Yeast energizer generally consists of a greater percentage of yeast hulls to absorb and neutralize fatty acids and other by-products that may build up and inhibit fermentation. Thus, yeast energizer is the choice for a stuck ferment, whereas yeast nutrient should be used for starters and before fermentation.

What is dry hopping?

Dry hopping is the process of adding fresh (unboiled) hops to the fermenter during fermentation. This increases the hoppy aroma of the beer, without contributing any bitterness because the hops aren’t boiled and the alpha acids will not be extracted. Adding hops to the primary fermenter is a primary dry hop, and to the secondary is a secondary dry hop. The hops don’t really need to be sanitized, as the essential oils and acids work as a natural preservative for the beer. If you choose to use a hop/grain sock before putting the hops in the fermenter, it is best to sanitize the sock with flash pasteurization or a no-rinse sanitizer.
The dry-hopped aroma will be the first thing to degrade in the beer, so it is best to package (bottle or keg) the beer after 3-5 days of contact with the hops.

What temperature should I ferment at?

In general, fermentation temperatures should be between 68°F and 72°F for ale, and 50° and 55° for lagers during primary fermentation. However, with the many variety of yeast strains available to homebrewers, many have optimum temperature ranges slightly above or below the general range. Consult the White Labs or Wyeast websites or information brochures (available on request) for more detailed information.

What’s the difference between ale and lager yeast?

Ale yeast (Saccharomyces cerevisiae) is a top-fermenting yeast that prefers warmer temperatures while lager yeast (Saccharomyces uvarum) is a bottom-fermenting yeast that prefers cooler temperatures. Ale yeast tends to be more vigorous and have a quicker turnaround compared to lager yeast that requires precise temperature/environment control and a longer conditioning time to produce the characteristic clean, crisp, and smooth lager flavor.

What is a pitch rate?

The pitch rate is the amount of yeast that you are adding to the wort to begin fermentation, usually expressed in amount of cells to add per volume of wort. For an average strength (O.G. 1.055-1.065) wort of 5 gallons, this is 110-170 billion cells.

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