• Day 1: Mix the flour and water together in a bowl until they form a stiff ball of dough. Do not worry if the dough is very stiff, but be sure that all the flour is hydrated. Press this piece of dough into a 4-cup measuring beaker (or any clear glass container) and place a piece of tape on the beaker to mark the top of the dough. Cover the beaker with plastic wrap and leave it at room temperature for 24 hours.
• Day 2: The dough should not have risen much, if at all, during this time. In a mixing bowl, combine the Day 2 ingredients with the Day l sponge, mixing with your hand or a spoon until all the ingredients are evenly distributed. The dough will be somewhat softer and wetter than the Day 1 sponge. Return this to the beaker, pressing it down, and replace the old tape with a new piece of tape to mark the spot. Cover with plastic wrap and ferment for 24 hours at room temperature. Do not be put off by the strong, unpleasant aroma of the dough. This will eventually brighten as it nears the finish line.
• Day 3: Check to see if there has been a rise in the dough. There will probably be some fermentation but not a lot, perhaps a 50 percent rise. Regardless, discard half of the starter (or give it to a friend to cultivate), and mix the remaining half with the Day 3 ingredients, as on the previous day. It will be a little wetter. Again, return it to the beaker. It should press down to the same height as on Day 2. Re-tape the beaker to mark the top of the dough, cover, and ferment for 24 hours.
• Day 4: The sponge should have at least doubled in size; more is even better. If it is still sluggish and hasn't doubled in size, allow it to sit out for another 12 to 24 hours. Otherwise, repeat as on Day 3, discarding half of the starter and mixing the remaining half with the new ingredients, returning it to the beaker as before. Cover and ferment until it at least doubles in size. This may take 4 to 24 hours. It is okay if it triples in size, but because it is now fairly soft and sponge-like, it will not be able to sustain that large of a rise without falling. If it falls easily when you tap the beaker, that is the sign that your seed culture is ready to be turned into a barm, or mother starter.

Barm

• Makes approximately 6 cups (2 1/2 pounds) barm
• 3 1/2 cups (16 ounces) unbleached high-gluten or bread flour
• 2 cups (16 ounces) water, at room temperature
• l cup (7 ounces) seed culture
• Stir together the flour, water, and seed culture in a mixing bowl (you can discard the remaining seed culture or give it to a friend to build into his or her own barm). Make sure the seed culture is evenly distributed and all the flour is hydrated. It will make a wet, sticky sponge similar to a poolish. Transfer this sponge to a clean plastic, glass, or ceramic storage container twice as large as the barm. When transferring the barm into the container, repeatedly dip your hand, spatula, or bowl scraper in water to keep the barm from sticking to it. Cover the container with a lid or plastic wrap and ferment at room temperature for approximately 6 hours, or until the barm is bubbly. The plastic wrap will swell like a balloon, as will a plastic lid. When this happens, open the lid or release the plastic to let the gas escape (try not to breathe it as it escapes - the carbonic gas mixed with ethanol fumes will knock you across the room!). Replace the cover and refrigerate overnight before using. The barm will be ready to use the next day and will remain potent for 3 days. After that, or if you use more than half during the next 3 days, you will need to refresh it as described next.

Refreshing the Barm

• The standard refreshment for barm is to double it at least. However, you can also quadruple it, as the organisms in the barm are capable of feeding on a large refreshment and converting it into starter. I double the barm at each feeding if I want a very sour bread, but I triple or quadruple it when I want a less sour flavor. Remember, it takes longer for the bacteria to work than the yeast, so while a larger feeding dilutes both the bacterial and the wild-yeast communities, the yeast bounces back faster than the bacteria, creating a strong, but less acidic, leavening sponge. Eventually, the bacterial fermentation does catch up, by the second or third day, and the sponge becomes quite acidic and sour (with a pH level of about 3.5).
• It is important to understand what happens when you refresh the barm. After 4 to 7 days, the acids and protease enzymes in a barm that has not been refreshed break down the gluten, turning what was at first a strong, stringy sponge into a protein-weak, potato-soup-like consistency. There are still plenty of live organisms to leaven and flavor bread, but they will make a flaccid dough. For this reason, it is advisable to feed your barm 3 days or less before you plan to use it (ideally, the day before). If you have a lot of barm but haven't fed it for a while, discard all but 1 cup and refresh it with 4 cups of flour and 2 1/2 to 3 cups water, stirring until all the flour is hydrated.
• If you have been using and feeding your barm regularly, you do not necessarily have to discard any. However, what you do not want to do is, for example, use l cup of barm from your supply to make some bread, then refresh the remaining barm with only l cup flour and some water. You must always at least double the remaining barm.You can do this by either throwing or giving some away before you refresh it, or using up more before refreshing it (remember, you have a 3-day window before you need to feed it again).
• If you do not plan to use the barm for a while, do not throw any away until you plan to refresh it again, and follow the guidance given above to refrigerate or freeze it in a tightly sealed container. Since you do not want to freeze a glass or ceramic container, you should transfer the barm to a zippered freezer bag that has been misted with spray oil (allow enough room for expansion and gas development).
• Use high-gluten flour for the refreshments (except in the case of a rye barm), as it has more gluten than in bread flour to withstand the acid and enzymatic degradation.
• You can refresh in two ways. One is to weigh the amount of barm you plan to refresh and the other is to eyeball it. I use both methods and find that as long as you stay in the doubling to quadrupling ballpark, you will have no problem keeping your mother strong, active, and clean tasting. By clean-tasting I mean that no off-flavors develop, such as a musty or cheesy flavor caused by over-fermenting at warm temperatures or by leaving it out too long. This allows unwelcome bacteria to join the party or for the yeast to create too much alcohol, resulting in what we think of as a yeasty flavor. The flavor is a combination of alcohol and glutathione, an unpleasant tasting amino acid released by yeast as it dies.
• The weighing method is simple: Weigh the barm and calculate how much flour and water it will take to double, triple, or quadruple the weight (the easiest way is to figure equal parts water and flour). Thus, if you plan to refresh 1 pound of barm, you can build it to 2 pounds by adding 8 ounces each of flour (1 3/4 cups) and water (1 cup); or you can quadruple it by adding 1 1/2 pounds flour (5 1/4 cups) and 1 1/2 pounds (3 cups) water. The larger the refreshment, the longer the fermentation time, usually 4 to 6 hours, depending on the size of the refreshment and how cold the barm was when you started. If you are using a cold barm just out of the refrigerator, warm the water up to about 90°F to compensate and to hasten the onset of fermentation. Never let the starter actually be warm, however. It is best for the organisms we want to cultivate, the lactic- and acetic-producing bacteria, if the starter ferments slowly, between 65° and 75°F, or at room temperature.
• When the starter is bubbly and foamy, put it in the refrigerator overnight before using it. Technically, though you could begin using it as soon as it foams up, but I wait for the overnight development because I believe it gives the bread more complexity of flavor. Either way, with a ripe and ready barm, you are ready to move on to the next build.