If the pickle jar is empty at first, you can pour boiling water into the empty jar and cover it (but you can't add water along the jar, otherwise when the water in the jar cools, the air in the jar will shrink and the water along the jar will be sucked into the jar).
If there are pickles in the jar, wait until the boiling water cools to room temperature before adding them to the jar. When making kimchi, it is necessary to keep the jar sealed along the water and cover it in time to prevent kimchi from deteriorating and producing substances harmful to human body. The new pickle jar can be fermented by adding some old jar water (available in the vegetable market). If you add some spices such as pepper, it will taste better.
The reason why the pickle jar is eight full:
Keep an appropriate amount of air for fermentation, which will become a vacuum after fermentation consumption, so as to prevent bacteria and leave only the needed fungi. Too much air is easy to breed bacteria, and too little air is not conducive to fungal reproduction.