Homebrewer’s Guide: Activator™ Smack-Pack System

Homebrewer’s Guide: Activator™ Smack-Pack System

The Wyeast Activator™ Smack-Pack System is the only product that “proofs” the yeast and shortens the lag time when it hits your wort. We often receive questions about our Smack-Packs. 

How do I store them? What temperature is best for storage? How long do they last?

We’ve compiled the most important need-to-know information when it comes to our Smack-Pack Activator System below!


Our packages contain a sterile liquid nutrient pouch when smacked, releasing its content into a yeast slurry. As the yeast consumes the sugars and nutrients, it generates CO₂, and the Activator™ swells. Although activation is not required before inoculation, it is beneficial and serves as a built-in viability and vitality test. If you choose to pitch directly without activating, the inner nutrient pouch doesn’t need to be cut open or included in your wort, as it is not a replacement for a nutrient blend.

The Activator keeps homebrewing simple. When our Activators are stored and handled correctly, there is no need to worry about calculating viable cells with online tools. The most accurate information is right in front of you: If the yeast produces enough CO₂ to create swelling in 3-5 hours, it is ready to pitch for a reliable, complete fermentation.

Each pack contains a minimum of 100 billion live yeast cells. All Wyeast yeast have a reliable cell count to avoid over or under-pitching. The slurry is packaged to optimize its shelf life while maintaining its ability for rapid and complete fermentation. 

All activator packs are designed for 5 gallons of standard gravity ale wort (1.060 SG). Depending on what you’re brewing, we recommend:

Warm Conditions: Inoculate wort at warmer temperatures (65-72 °F, 18-22 °C) for lagers, wait for signs of fermentation, then adjust to your desired temperature. 

Cold Conditions/High Gravity: We recommend increasing pitch rates for additional gravity, temperature, and style pitch rate recommendations. Lagers and high gravity fermentations require at least twice as much yeast as standard gravity ale brewing.


How do I ensure I am properly using my Smack-Pack?

To make sure you are correctly using your Activator™, make sure you follow proper storage instructions. Packs should be kept refrigerated between 34-40 °F (1-4 °C) and never frozen. Note that older yeast or yeast exposed to higher or lower temperatures may take longer to become active or swell. If you are ordering yeast online, make sure it is shipped with ice, insulation, and arrives promptly. Or, visit your Local Homebrew Shop to pick up your favorite strain to avoid any shipping concerns.

1. When ready to pitch, remove the Activator™ from the refrigerator and allow it to come to room temperature just prior to use

2. Activate the pack by firmly smacking to break open the inner nutrient pouch, shake to release nutrients (we recommend cornering the inner pouch for easiest results)

3. Allow the package to swell for 3-5 hours

4. Sanitize the package before opening 

5. Shake well, open and pour the Activator™ into 5 gallons (19 L) of well-aerated or oxygenated wort up to 1.060 OG at 65-72 °F (18-22 °C). Maintain temperature until fermentation is evident by CO₂ bubble formation, bubbling airlock, or foaming on top of wort. For high gravity or low-temperature fermentations, additional yeast may be required.

6. Adjust to desired fermentation temperature. For more information on temperature selection, visit our YEAST STRAINS section and select the strain being used.


How long do I have to use my Activator packs?

Our Product Warranty guarantees the viability of the yeast in our Activator™ packages for a minimum of 6 months, assuming that they have been properly shipped, stored, and handled. Our packaging material provides a 100% oxygen barrier and UV light protection. 

During shelf life, some loss of viability is to be expected. This will vary from one strain to another. Activator™ packages within 2 months of the ‘Best if Used By’ date may require additional time to swell after activation.


For more details on our Activator™ Smack-Pack System, visit our website for complete information, find brewing supply stores near you carrying Wyeast Lab Activators!

Join our newsletter