Grace, I honestly don't think you can say that a floating starter, no matter how long it floats, is proof that it's fully ripe. My tests show that a starter that isn't ripe will float; and will remain floating until it gradually absorbs the water in which it's floating and disintegrates and sinks. So I wouldn't trust the float test — except to note that a starter that immediately sinks and stays on the bottom isn't ready to use. Hope that makes sense! PJH@KAF

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