These are 5-month-old sourdough rye bread crumbs. They are my bread kvass starter. I’ve been using the this same sourdough bread over and over again to make a bottle of fermented kvass each week since March. . The more time passes the stronger the starter gets. I know this as my kvass has been turning sour more quickly. . Swipe to see the sugar that I use, the rye bread settled in the bottom of the jar ready to start its work, and the strained, bottled kvass second-fermenting with some fresh mint from the garden.