W-34/70 is Fermentis's neutral lager starting point; S-23 is positioned for fruitier, more estery lagers. Both products currently list an ideal fermentation interval of 12–18°C and a dosage of 80–120 g/hL. Shared instructions do not make them the same yeast or guarantee the same flavour.
Start with two questions: what fermentation character does your recipe need, and can your equipment maintain the chosen beer temperature? This guide compares manufacturer guidance and builds a planning exercise. BrewMyBeer has not performed the side-by-side lager tasting described below.
What the supplier says about each lager yeast
| Planning point | W-34/70 | S-23 |
|---|---|---|
| Supplier's origin description | Weihenstephan, Germany | Berlin, Germany |
| Flavour direction | Clean lager profile with balanced floral and fruity aromas | Fruitier, more estery lager profile |
| Listed ideal temperature | 12–18°C | 12–18°C |
| Listed dosage | 80–120 g/hL | 80–120 g/hL |
Primary references: Fermentis W-34/70 and Fermentis S-23. Both are sold as Saccharomyces pastorianus. A shared species name is not a complete sensory description. No particular peach note, finishing gravity or clarity ranking is promised here.
A temperature study is not a fixed schedule
Fermentis's W-34/70 characterization study reports that higher temperatures shortened fermentation while preserving a neutral profile in the tested conditions. It also flags diacetyl risk when low pitching rate and low temperature occur together. It does not supply a universal “ready in seven days” promise.
The study concerns W-34/70; it does not establish an identical response for S-23. Its planning lesson is to consider wort density, pitch and temperature together. Review a recipe copied from a colder process before making it a warmer one. Record measured beer temperature rather than assuming a room thermometer describes the liquid inside the fermenter.
How much dry yeast does a 20-litre batch imply?
Convert g/hL with grams = litres × dose ÷ 100. Under the published 80–120 g/hL interval, 20 litres corresponds to 16–24 g. Exactly one 11.5 g sachet in 20 litres is 57.5 g/hL, below that interval. In 10 litres, that same sachet is 115 g/hL, inside it.
This is arithmetic using supplier guidance, not a diagnosis of a previous batch or a special rule for high-gravity wort. Check the instructions for your product and conditions. Write fermenter volume beside yeast mass; “one packet” conceals both. The calculator directory supports planning, but a cell-based estimate and a product's mass guidance are different inputs.
For a hypothetical equal split of 20 litres, each 10-litre vessel has a listed planning interval of 8–12 g. Choose and document a rate within the relevant guidance before dividing supplies. Record weighed mass rather than assuming casually divided portions are equal.
A lager comparison with one clear question
Use the brief: “Can I distinguish the yeast character in this wort under the same temperature plan?” The goal is a record another learner can understand, not a predetermined winner.
- Hold the recipe constant. Divide one homogeneous wort into labelled vessels. Record actual starting gravity and volume in each.
- Choose one comparison variable. Change yeast while keeping the intended dosage rate and temperature plan comparable. A hypothetical 14°C setting sits inside both listed intervals; it is a trial choice, not a universal optimum.
- Log the process. Record yeast lot, mass, pitch time, temperature readings and measured gravity. Retain unexpected results.
- Keep conditioning comparable. Document any difference in timing or handling before interpreting flavour differences as a yeast effect.
- Compare coded samples. Record aroma, appearance and preference separately. “Different,” “preferred” and “better matched to my recipe” are distinct conclusions.
Do not publish an exact finishing schedule based on a supplier range or a gravity prediction. A simulation's representative timeline is a learning model, not a packaging instruction. To explore decisions before using ingredients, start an account-saved brewery simulation.
Choose a starting point and keep the evidence
For a brief calling for restrained fermentation character, W-34/70 matches the supplier's positioning. If the brief welcomes a more expressive lager profile, S-23 is a candidate to compare. These are editorial selections, not guarantees of a medal or an exact commercial beer clone.
Before ordering, check the strain label, batch volume, storage instructions and temperature-control plan. A substitute is useful only if its guidance and intended character suit the batch. The WLP830 reference describes a separate liquid-yeast option; it does not establish genetic or operational identity with either dry product.
Quick planning challenge
Why can one 11.5 g packet fit the listed dose for 10 litres but not 20 litres?
The rate depends on volume: 11.5 × 100 ÷ 10 = 115 g/hL; 11.5 × 100 ÷ 20 = 57.5 g/hL. Compare those figures with current 80–120 g/hL guidance. The calculation does not predict the finished beer or authorize packaging.