When do I need multi-step propagation?

When starting from a slant, plate, or very old yeast with few viable cells. A single starter may not grow enough cells from a tiny starting culture.

How long between steps?

Allow 24-36 hours per step on a stir plate. Decant the spent starter wort before stepping up to the next volume.

What size flask do I need?

Your flask should be at least twice the volume of your largest starter step to allow for foam. A 2L or 5L flask covers most propagation needs.

Can I propagate yeast from a bottle of commercial beer?

Yes, if the beer is bottle-conditioned with the original brewing yeast. Pour the beer, leaving the sediment, add it to a small starter (100-200ml), and step up over several days. Not all bottle yeast is the same strain used for primary fermentation.

How do I know if my propagation was successful?

A successful starter will show activity within 12-24 hours: krausen formation, CO2 bubbles, and a yeasty smell. After 24-36 hours on a stir plate, you should see a milky white sediment when you stop the plate. No activity after 48 hours suggests the culture may not be viable.

BrewCalcs

Yeast Propagation Calculator

Plan multi-step propagation to build yeast from a small culture.

Initial Cell Count

Target Cell Count

How We Calculate This

Multi-Step Propagation

Each propagation step roughly doubles the cell count when using a stir plate. The calculator plans steps that gradually increase in volume, allowing the yeast population to grow to pitching levels from a very small starting culture.

Frequently Asked Questions

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Last updated: 2025-02-20

All calculations are estimates. Always verify values and adjust based on your equipment and ingredients.