The Complete Guide to Kefir Making Equipment

Published 6th January 2022 · Updated 11th December 2025

You don’t need a fancy lab to brew delicious kefir at home, but using the right tools is vital for the health of your grains. This guide covers everything you need, explaining why certain materials like glass and plastic are preferred over reactive metals.

The Golden Rule: Avoid Reactive Metals

Kefir grains create an acidic environment during fermentation. This acid can react with certain metals like aluminum, copper, iron, and brass. Prolonged contact can damage your grains and potentially leach metallic ions into your drink.

However, modern food-grade stainless steel is generally safe for brief contact, like stirring or quick straining. But for fermentation vessels and long-term storage, we always recommend inert materials.

Best Materials: Glass, Food-Grade Plastic, Ceramic, Wood.

Your Kefir Equipment Checklist

Here are the essential tools you’ll need for brewing both milk and water kefir efficiently and safely.

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1. Fermentation Jar (Glass)

Glass is the best material because it’s non-reactive, easy to clean, and lets you see what’s happening inside. A wide-mouth mason jar (1 liter or 1 quart size) is ideal for most home brewers.

Avoid: Metal containers or crystal (which may contain lead).

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2. Breathable Cover & Band

Fermentation produces gases that need to escape. Do not use an airtight lid during the primary fermentation. Use a breathable cloth, a coffee filter, or a paper towel secured with a strong rubber band. This keeps fruit flies and dust out while letting the mixture breathe.

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3. The Strainer (Plastic or Nylon)

To separate your finished drink from the grains, you need a sieve. We strongly recommend a plastic or nylon mesh strainer. This eliminates any risk of metal reactions. While stainless steel is usually okay for quick straining, plastic is the worry-free choice.

A plastic or nylon sieve is the safest choice.

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4. Spoon & Bowl

You’ll need a bowl to catch the strained kefir and a spoon to gently help the liquid pass through the sieve. Again, plastic, wood, or stainless steel spoons are fine. Avoid older, tarnished, or reactive metal spoons.

Frequently Asked Questions About Gear

Is stainless steel harmful to fermentation?

Modern, high-quality food-grade stainless steel is generally considered inert enough for short-term contact with kefir, such as stirring with a spoon or using a stainless steel sieve for a minute. It will not harm your grains or SCOBY instantly. However, we still recommend plastic/nylon sieves as the safest, foolproof option, especially for beginners. Avoid leaving stainless steel utensils sitting in the fermenting jar long-term.

What kind of jars should I absolutely avoid?

Never use containers made of reactive metals like aluminum, copper, iron, or brass. Also avoid crystal (which can leach lead) and ceramic containers that are not certified food-safe, as some glazes contain heavy metals that can leach out in acidic environments.

Can I use a bamboo strainer?

Yes, bamboo strainers are safe as they are non-reactive wood. However, they can be harder to keep hygienically clean over time compared to plastic, as wood is porous and can trap bacteria or mold if not dried properly.

Get All the Right Tools in One Kit

Don’t want to hunt for individual items? Get a complete starter kit that includes fresh grains and the correct, safe equipment.

Deluxe Kefir Starter Kit

Includes fresh grains, a fermentation jar, a culture-safe plastic strainer set, a breathable cover, and instructions.

🛒 Buy the Complete Starter Kit