For fermentation in general, let me give you a few tips that may be tripping you up:

1. Don’t wash ANYTHING in chlorinated water before going in the jar.

2. The salt type and granule size is very important.

3. Always calculate salt by total weight of the liquid + contents going in the jar

4. NEVER add chlorinated water to the vessel. NEVER EVER EVER

Some tips for Kimchi specifically:

1. Smash the garlic and let it sit for a few minutes before chopping or adding

2. Get the finest granule of pepper “flakes”. Not the large flake kind meant for soups or stews. You want powder, practically. Deep red, and about the grain of table salt at max.

3. Mix your salt, sugar, pepper flakes, garlic and onion FIRST before adding them to your cabbage. A little bit of soy sauce or spring water for moisture. Let the mixture sit a good 30m to bloom before rubbing into the cabbage.

4. RUB THAT MIX ALLLLLL OVER EVERRRRRYTHING. When I say everything, that means every little nook and cranny of the cabbage. Squeeze the cabbage a bit while doing so to help release some moisture into the marinade.

5. Get a muddler to help smash and bruise the cabbage as it’s going into your jar. You really want it packed tight, and smashing it as you go releases even more moisture into the mix, so by the time you’ve filled the jar, you should have enough volume to mostly cover the top

6. Get some weights for the top to make sure the last bits added are submerged.

Good luck.