Start by wiping the stems with a damp cloth, but do not soak them in water. Then, cut them into pieces of +/- 1 cm and into 2 or 4 lengthwise depending on the size and put them in the freezer for at least 48 hours.

On the day of preparation, place the rhubarb pieces in one or more colanders covered with a cloth and placed over a container. Defrosting will soften the rhubarb, and the juice will naturally be extracted.

Squeeze as much of the rhubarb as possible by pressing it through a cloth or using a juicer. You should harvest 5 liters of pure juice without adding any water.

Mix the calcium carbonate into the liquid and let it sit for about 3 hours. The oxalic acid in the rhubarb will then convert to calcium oxalate. Skim off any foam if necessary and strain the liquid through a cheesecloth placed in a strainer.

Melt the sugar over very low heat in the 2 liters of water to obtain a syrup, then let it cool completely.

Scrub the lime skin and remove half of the zest. Cut the peeled orange and lemons into pieces. Add them to the liquid along with the zest after removing the whitish part and cutting it into pieces. Cut the ginger into small cubes and add them to the liquid as well.

Dissolve the sourdough in a container with a little liquid, then add it to the liquid with the yeast salt after ensuring that the temperature of the liquid does not exceed 25°C.

Pour the liquid into a demijohn fitted with a water-filled bubbler cap, then place in a place where the temperature is maintained between +/- 18 and 25 °C. Shake very often at the beginning of fermentation until it starts. Fermentation lasts approximately 25 to 30 days.

After this time, filter to remove the ginger as well as the zest and pieces of citrus fruit and decant again in the same well-cleaned demijohn, still equipped with its airlock stopper. Then let it decant for at least 6 months before bottling, taking care to rack carefully.