Lacto-fermented radishes are not as common as other fermented vegetables but this recipe is so simple that it just might become a staple in your kitchen.
The fermentation process gives off carbon dioxide and this can increase the pressure in the jars and even explode them if the pressure is not released. Simply open the jars once a day. You can also pour off some of the brine if it starts to rise towards the top of the jar. Alternatively, you can use an airlocks lids (find a good product here) that allows the gasses to easily escape.