How to Activate Wyeast Smack Packs (Liquid Yeast)

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Wyeast Activator Packs are liquid yeast pouches used by homebrewers to achieve authentic, strain-specific flavors in beer. But before you pitch them into your wort, you must activate them properly. This guide gives beginner-friendly instructions to help you activate Wyeast yeast successfully and avoid common mistakes.

1. Refrigerate Immediately

As soon as you receive your Wyeast pack, refrigerate it. Whether purchased in-store or online, cold storage is essential for maintaining yeast viability.

2. Check the Manufacturing Date

On the front of each pack is a stamped "MFG" date (e.g., "28MAY24"). Use this date to estimate freshness:

  • 1–2 months old: Activate on brew day; ready in 3–6 hours.
  • 2–3 months old: Activate ~24 hours in advance.
  • 4–6 months old: May require 48 hours or more to swell.

Note: If your yeast arrived warm from shipping, don’t wait months to brew with it. Use it soon for best results.

3. Activate the Pack

Inside each Wyeast pack is a nutrient pouch. Smack the pack to break it open and begin the activation process.

  • Move the inner pouch to a corner and smack the pack with your hand.
  • Feel around to confirm the pouch is broken — this is essential.
  • Shake vigorously to mix nutrients and yeast.

4. Incubate at the Right Temperature

Let the activated pack sit at 70–75°F (21–24°C). Use a warm area like the top of a cable box. Pack swelling may take:

  • Fresh packs: 3–6 hours
  • Older packs: 24–48 hours

Ensure the pack swells noticeably. If you’re unsure, it probably hasn’t swelled enough yet.

5. Sanitize Before Opening

Wipe the outside with sanitizer. Use sanitized scissors to cut open the pouch. Consider using a brewing-dedicated pair of scissors to avoid kitchen grime.

6. Shake and Pitch

Shake again to loosen yeast. Open and pour into oxygenated wort. Yeast need oxygen during pitching to reproduce and ferment well. Don’t skip this step — give the fermenter a vigorous shake.

7. High Gravity Beers Need More Yeast

Wyeast packs are designed for beers with original gravity (OG) ≤ 1.060. For bigger beers, use a yeast starter or pitch multiple packs to avoid underpitching and stalled fermentation.

8. Pitch at the Correct Temperature

Pitch the yeast into wort at 65–75°F. We recommend pitching at 75°F and insulating the fermenter with a blanket. Once fermentation begins, move it to your desired fermentation temperature.

Frequently Asked Questions

What is a Wyeast Smack Pack?

A liquid yeast pouch with an inner nutrient pack. Smacking the pack releases the nutrients and activates the yeast before pitching.

How long does it take to swell?

Fresh packs: 3–6 hours. Older packs: 24–48 hours. Always base your timing on the age of the yeast.

My pack isn’t swelling. What should I do?

Confirm the nutrient pack is broken and incubate at 70–75°F. Older yeast or yeast exposed to heat may need more time — or a yeast starter.

Can I pitch before it swells?

Technically yes, but swelling indicates healthy, active yeast. For best fermentation, wait for visible swelling before pitching.