One of the dangers of lactofermenting foods is that it produces carbon dioxide as a byproduct. When putting lactofermented foods in a jar and sealing the lid, this gas can build up.
Seen here is an example of what can happen when fermenting (culturing) fresh ground grains. See how the lid is bulging? This thing is about to explode!
I opened the lid very slowly in the kitchen sink to release some of the gas. Be very careful because the lid can literally blow off and you'll have a big mess. I managed to open it slowly enough so this didn't happen (thankfully).
Keep an eye on newly lactofermented foods. You can place them in the fridge to slow down this process. Sitting in a warm spot in the kitchen will cause this process to happen much faster.
With fermented grains, be careful not to fill the jar too close to the top (as I did here). You should fill only half the jar, including water, when you create your batter. Add a bit of yogurt to begin the fermentation. It's that simple.
Following Weston A. Price