To attention of my friend Elumalay, I did ask to Google translate my previous post

So I need

100 to 150 g of dried grapes Corinth (Bio and untreated!)  I think red are better than yellow.

1 teaspoonful of pure honey without additives or added sugars (finally honey, what!)

In a quarter of a liter of soft water

Let it rest in the sun if possible, but not more than 35 ° C, in a non-sealed glass container, Rather covered with a stamen to avoid insects.

After a few days, depending on the temperature and the sunshine, a light foam forms (just bubbles) and the grapes rise to the surface.

If you see mold, you miss it, start again with a very clean container in a more controlled atmosphere.

If it’s too cold and the yeasts are still growing, your sourdough will be sour. Some will prefer it, but for me, I try to have it soft enough.

Use the preparation to knead dough with 500 g flour. When it has risen, this dough will serve to prepare a “polish” or a sourdough. Do not be surprised if it rises slowly in the first times: it is necessary to leave time to the yeasts to multiply and to strengthen.

By kneading the first batch, do not forget to reserve a piece to start again later!

Your leaven is started. Allow it time to light up slightly before re-using it. Keep the sourdough fresh, especially if it has to wait several days before being re-used. Avoid the temperature exceeding 30 ° to favor the best yeasts. Work always in the same room: the air will be loaded with spores that will replenish the new preparations;

If you want to keep a leaven more than a week, do not freeze, just in the fridge by re-working the dough regularly to feed it. For a longer period, let a large ball to dry and re-moisten it to restart.

But a leaven is not eternal. It can be spoiled, faded. The Hebrews renewed it every year at Easter, contenting themselves with unleavened bread (azyme) for a week. This habit will give you the opportunity to occasionally eat bread from another baker.