Whenever you’re maintaining an active, full-strength starter, you always need to at least double its weight to keep it healthy and happy. That can be a lot of starter assuming you keep it going at room temperature…two ounces makes four ounces make eight ounces make a pound and so on. Do that every day for a week and shortly you’d grow The Blob. Anybody seen Rex?
But what if you want that kind of exponential growth? Say, if you suddenly had a lot of bread you wanted to make, but only had a cup or so of starter to work with? The good news is that an active starter can be refreshed with up to three times its weight in flour-water mix (quadrupled) and still produce a sponge in the same timeframe. The down side is that it won’t taste as complex as a starter that’s only been doubled in weight.
Why? Because your average yeast grows a lot faster than your average lactic acid bacteria. Since those bacteria are what are responsible for much of the flavor in a starter, you’ll get a very mild-tasting bread. That can be a good thing of course. Many bakers manipulate their starters in just this way to produce either very sour or not-at-all-sour breads by “natural” means.