To bake sourdough is to be a custodian of a living thing. The starter—that bubbling, breathing culture of wild yeast and bacteria—is the heart of the loaf. It’s a partner in the baking process, with its own rhythms, needs, and moods. And as any baker knows, its vitality is profoundly tied to temperature.
The Baker’s Dilemma
Our modern kitchens are rarely the ideal environment for this ancient lifeform. Temperatures swing with the seasons, the time of day, or whether the oven has been on. In winter, a starter can be sluggish, refusing to rise with the vigour needed for a great bake. In summer, it can ferment too quickly, becoming overly acidic and losing its strength.
We are left to improvise, seeking a ‘warmish, not-hot’ spot, or trying to time our bakes around the unpredictable temperament of our home’s climate. The challenge is twofold: keeping the starter healthy but dormant during days of rest, and waking it to peak activity precisely when we want to mix our dough.
A Dedicated Home for Your Starter
The Hearth Keeper is our answer to this challenge. It is a small, dedicated, temperature-controlled home for your sourdough starter—a companion to help you tend to the living heart of your bread. It is a project designed to bring predictability and peace of mind to your baking rhythm.
The Hearth Keeper is designed to perform two primary functions:
- Dormancy (Keeping): It maintains a steady, cool temperature (around 5-10°C), allowing you to store your starter for days or a week at a time without the need for daily feedings. This is for the quiet times between bakes.
- Readiness (Waking): At your command, or on a pre-set schedule, it gently warms the environment to the ideal temperature (around 24-28°C), waking the culture from its slumber and bringing it to peak activity, bubbling and ready for baking.
Technology in Service of Tradition
This is a project where modern, open-source technology serves an ancient craft. By integrating with platforms like Home Assistant, the Hearth Keeper becomes a truly intelligent part of your home. Imagine telling your smart home system, “I’m baking on Saturday morning,” and having the Keeper automatically begin warming your starter on Friday evening, ensuring it’s perfectly ripe and ready when you are.
At its core, the device is simple, built on the same principles as our DIY Fermentation Chamber:
- An insulated chamber to hold one or two jars of starter.
- An ESP32 microcontroller as the brain.
- A Peltier thermoelectric module which can both heat and cool, providing precise temperature control in a single, elegant component.
- A sensor to constantly monitor the environment.
This is the SEIN philosophy in practice: using accessible technology to deepen our connection to timeless, hands-on processes. It helps us listen more closely to the living systems we are a part of, and to collaborate with them more intentionally.
Join the Baking Circle
The Hearth Keeper is an open-source project, and we invite fellow bakers, makers, and technologists to join us. Whether you have ideas for the design, experience with microcontrollers, or simply a passion for the perfect sourdough loaf, your contribution is welcome.
Let’s build a community of makers dedicated to this beautiful craft, sharing our knowledge and our love for bread made with patience, care, and a little help from our microbial friends.
This is an active project. We will be sharing build guides, schematics, and open-source code as they are developed.