How to Make Water Kefir at Home: A First and Second Ferment

What you need

You need water kefir grains, plain sugar, water, a clean glass jar, a breathable cover and a plastic or stainless steel strainer. Sugar is the grains' food, and the mix is usually about a quarter cup of sugar per quart of water, with one to three tablespoons of grains. Many brewers also add a pinch of mineral-rich ingredients such as a little unsulfured dried fruit, a slice of lemon or a bit of unrefined sugar, because the grains benefit from minerals.

Use water without heavy chlorine, such as filtered water or tap water that has stood for a while, and avoid distilled water for the long term because it lacks minerals. Avoid prolonged contact between grains and reactive metals, so use plastic, wood or stainless steel utensils. Our water kefir kit guide compares starter kits that include grains and equipment.

Compare water kefir kits →

The first ferment

Dissolve the sugar in a little warm water, then top up with cool water until the mix is at room temperature. Hot water can damage the grains. Pour it into the jar, add the grains, and cover with a cloth or coffee filter. Leave it at room temperature, away from direct sunlight, for about 24 to 48 hours.

The liquid will become slightly cloudy, may develop small bubbles, and the sweetness will drop as the microbes use the sugar. Taste it after a day. If it still tastes very sweet, give it more time. Warmer rooms ferment faster, and cooler ones slower. When it tastes pleasantly less sweet, strain out the grains and start the next batch immediately.

The second ferment for flavor and fizz

Pour the strained kefir water into sturdy bottles with tight seals, such as swing-top bottles, adding about a tablespoon or two of fruit juice, a few pieces of fruit, a slice of ginger or a sprig of herbs per bottle. Leave about an inch of space at the top. Seal and leave at room temperature for 12 to 48 hours, then chill.

The sugars in the fruit feed the remaining yeast, which makes carbon dioxide and builds pressure. Open bottles slowly, ideally after chilling, and over a sink. Use bottles made for carbonated drinks, never thin or cracked glass. Our swing-top bottle and bottling funnel guides cover handy tools for this stage, and our kombucha flavoring ideas apply here too.

Compare swing-top bottles →

Caring for the grains

Feed the grains with fresh sugar water every one to two days at room temperature. Over time the grains grow and multiply, and you can share extras or reduce the amount. If you need a break, put the grains in fresh sugar water in the refrigerator for up to a couple of weeks, then return to room temperature and feed them. Some people dry or freeze grains as a backup, though results vary.

Healthy grains are translucent and plump. They can shrink or turn cloudy when stressed by too little sugar, too much heat or lack of minerals. Rinsing is generally unnecessary, but if you do, use non-chlorinated water. If the grains stop multiplying or the drink tastes flat, try a different sugar, a pinch of minerals or a warmer spot for a few batches.

Flavor ideas for the second ferment

Good starting combinations include ginger with lemon, berries with a little mint, pineapple with a pinch of turmeric, or a splash of apple juice with a cinnamon stick. Fresh or frozen fruit both work, and dried fruit such as figs or raisins can add sweetness and minerals. Strong flavorings like fresh ginger tend to carbonate faster, so check those bottles sooner.

Keep the amount of added sugar or juice modest at first. More sugar means more pressure, and an overfilled bottle with a lot of juice is the most likely to gush or burst. Straining out large fruit pieces before bottling makes pouring cleaner, and a funnel with a fine strainer helps keep the grains and pulp out of the bottle.

Troubleshooting

If the batch tastes too sweet, it needs more time or warmth. If it is thin and sour with little sweetness, it is over-fermented, so shorten the time. A yeasty or beery smell is usually a sign of too much yeast or too long a ferment. A slimy or ropey texture can appear temporarily and often resolves with fresh sugar water and a few batches.

Mold on the surface, usually fuzzy, is a sign to discard the batch and wash the jar. Sulfur-like smells that persist, or pink or black growth, also call for a fresh start. Cleanliness, enough sugar and stable temperatures prevent most problems. Use clean utensils every time, and wash your hands before handling grains.

Safety and what to expect

Water kefir contains small amounts of alcohol from fermentation, and the exact amount is difficult to measure at home, especially after a sealed second ferment. It is not intended for children or anyone avoiding alcohol. People who are pregnant, have weakened immune systems or take medications should ask a doctor before drinking it.

Expect a mildly sweet, tangy flavor and gentle fizz rather than the strong sweetness of commercial soda. The taste changes with sugar type, fruit, time and temperature, so treat the first batches as experiments. Keep notes on timings and flavors and adjust one thing at a time until you find a routine that fits your kitchen.