About S.D TIMER — Sourdough Starter Scheduler
S.D TIMER is a professional sourdough starter scheduling tool built for bakers who want precise, science-based feeding plans. Enter your target bake time, ambient temperature, flour type, and hydration ratio, and the app calculates exactly when and how much to feed your starter so it peaks at the right moment.
Developed by Water & Flour Workshops, a sourdough bakery and baking school based in Tel Aviv, Israel, S.D TIMER reflects years of hands-on fermentation experience combined with rigorous understanding of the microbiology and chemistry involved in leavening bread with wild cultures.
The Science Behind Sourdough Fermentation
A sourdough starter is a stable, symbiotic culture of wild Saccharomyces cerevisiae and lactic acid bacteria (LAB), primarily Lactobacillus species. Fermentation rate is governed by three coupled variables:
Temperature: Enzymatic and microbial reaction rates follow Arrhenius kinetics — roughly doubling for every 10 °C increase within the viable range (4–40 °C). At 22 °C a 1:5:5 feed (starter:flour:water by weight) typically peaks in 10–12 hours; at 28 °C the same feed peaks in 4–6 hours.
Inoculation ratio: The proportion of mature starter to fresh flour controls lag phase duration and the total buffering capacity of the dough. Lower inoculation (1:10:10 or 1:20:20) extends fermentation time and increases acetic acid production, yielding more pronounced tang. Higher inoculation (1:2:2) shortens fermentation and favors milder, lactic flavors.
Flour composition: Whole-grain flours (whole wheat, rye) carry higher ambient microbial populations and more fermentable sugars and minerals, accelerating fermentation by 15–30% compared to white bread flour. The ash content and damaged starch percentage directly affect amylase activity and sugar availability for the culture.
How S.D TIMER Calculates Your Schedule
The app uses empirically-calibrated fermentation curves to map temperature × inoculation ratio × flour type onto a projected peak time. You input when you need the levain to be ripe (for example, 6:00 AM on bake day), and the calculator works backward to determine the exact feeding time the night before, including how much starter, flour, and water to use.
This eliminates guesswork from the most variable stage in sourdough bread making — the build. Instead of relying on visual cues alone (the float test, dome height, or aroma), you have a quantitative schedule grounded in your specific environment and feeding protocol.
Frequently Asked Questions
What is a sourdough starter?
A sourdough starter (also called a levain, chef, or mother dough) is a fermented mixture of flour and water that captures and maintains wild yeast and bacteria from the environment and the flour itself. When mature, it provides both leavening power (CO₂ production) and flavor development (organic acids) to bread dough without commercial yeast.
How do I know when my starter has peaked?
A ripe starter reaches maximum volume — typically 2× to 3× its fed volume — then begins to recede. Visual cues include a domed or flat top, visible bubbles throughout the culture, a clean yeasty-tangy aroma, and a webby structure on the sides of the jar. S.D TIMER times your feed so this peak aligns with your planned mix time.
Why does temperature matter so much?
Temperature is the single largest variable in fermentation timing. A starter that peaks in 8 hours at 24 °C may take 14+ hours at 18 °C or only 4 hours at 30 °C. Kitchens vary seasonally, so inputting your actual ambient temperature into S.D TIMER is essential for accurate scheduling.
What is hydration in a sourdough starter?
Hydration refers to the ratio of water to flour by weight. A 100% hydration starter uses equal weights of flour and water (e.g., 50g flour + 50g water). Lower hydration starters (60–80%) ferment more slowly and tend toward more acetic (vinegary) acids; higher hydration starters ferment faster and produce more lactic (mild, creamy) acids.
Can I use this app for different flour types?
Yes. S.D TIMER supports white bread flour, whole wheat, rye, and spelt, each calibrated with different fermentation multipliers based on their respective amylase activity, ash content, and native microbial load.
Is S.D TIMER free to use?
Yes, the web app is completely free and runs in any modern browser with no login required. A Pro version is available with an ad-free experience and additional advanced features.
About Water & Flour Workshops
Water & Flour Workshops (waterandflour.co.il) is a Tel Aviv–based sourdough bakery and professional baking education studio. We run hands-on workshops on sourdough bread, laminated doughs, and open-crumb techniques for home bakers and food professionals. S.D TIMER was developed as a tool for our students and the wider sourdough community.
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