A rye starter is basically the same thing as a white or whole wheat starter: a fermented mass of wet flour, only with rye flour as a base instead of some other type. Rye flours are quick to ferment for reasons that will be discussed later this week, meaning you can make one in a bout half the time of a white wheat starter: about three days. All you need to do is mix maybe an ounce of rye flour with an ounce of water, stir it and let it sit out overnight. The next day add two ounces of rye flour and two ounces of water and again let it sit out overnight. The next day add four ounces of rye flour and four ounces of water…and you should have a ready starter about four hours later. Bingo.
Me, since I always have some white starter around, so I like to start with that and simply change the food. Here I’ve got an ounce of very active and bubbly (just fed about two hours before) white flour starter.
I add an ounce of rye flour…
…and an ounce of water…
Four hours or so later it looks like this. Not much appears to have changed save that it’s puffier and there are a few little black bubble holes in it.
However under the surface you can see that there’s activity. See the bubbles spaces in there?
This can be used right away. For a “truer” rye starter, feed it a second time (doubling its weight with a 50-50 flour-water mixture) and leave it out overnight. Feed it once more in the morning or later that day, let it rise about 3-4 hours and use!