Small-batch whole-wheat sourdough starter

Volumes are approximate. For baking, use a scale; Metric keeps the specified gram weights.

• 21.16 oz whole-wheat flour, a feeding supply; not all will be used
• 21.16 oz unbleached bread flour, a feeding supply; not all will be used
• 2.65 lb drinking water, a feeding supply; not all will be used

Let’s make it

1. Use a clean 2 cups + 1 tbsp + 2 ½ tsp–3 cups + 2 tbsp + 2 ⅛ tsp straight-sided food-safe jar and a kitchen scale. Mix 1.06 oz whole-wheat flour with 1.06 oz water in the jar. Cover with a loose lid, never an airtight seal, and keep at about 70–75°F (21–24°C), away from direct heat. Mark the starting height.
2. After 24 hours, retain 0.705 oz of the mixture in a clean jar and discard the rest. Feed with 0.705 oz whole-wheat flour, 0.705 oz bread flour and 1.41 oz water. Stir well, mark the height and loosely cover.
3. From day 3 onward, repeat the same feeding about every 12 hours: retain 0.705 oz starter and add 0.705 oz whole-wheat flour, 0.705 oz bread flour and 1.41 oz water. This makes 3.53 oz after each feeding. Keep the jar rim clean. The listed supplies cover about 14 days, including a final build; buy more if development takes longer.
4. An early burst of bubbles can subside and does not establish readiness. Continue until the starter repeatedly at least doubles within about 6–8 hours after feeding, with bubbles throughout and a pleasantly sour aroma, over several consecutive feeds. Many starters take 7–14 days or longer. The stated 14 days is planning time, not a guarantee.
5. Discard the entire culture if you see fuzzy mold, pink or orange discoloration, or a putrid smell. Do not scrape off contamination and keep the rest. Never taste raw starter or raw flour. Discard from this establishment period should be thrown away rather than eaten or used in cooking.
6. Once reliably active, retain 1.06 oz starter and feed 1.06 oz whole-wheat flour, 1.06 oz bread flour and 2.12 oz water. Let it rise until active; this final build yields about 5.29 oz at equal flour-and-water weight overall. Use 3.53 oz in the linked bread recipe and retain 1.76 oz to maintain. This is a culture yield, not one edible serving.
7. For ongoing care, feed a retained portion with an equal combined flour weight and an equal water weight as above. Keep loosely covered at room temperature with regular feeding, or refrigerate a mature fed starter and refresh at least weekly. Before baking, allow enough room-temperature feedings to regain reliable growth. Follow the separate bread method to fully bake any dough.