Tip into a sturdy zip-lock bag or pour-and-store bag, or a glass jar using the bag-of-brine method. This ferment can get very over-excited, so a sealed glass jar could potentially present an explosive situation, and the valve of a vented jar could get blocked. If you really want to use a Kilner jar, consider replacing the metal catch with a rubber band that would give way long before a harmful pressure build-up could occur. As the sauce ferments, it separates, with a thick cloud of pepper mash rising to the top as CO2 bubbles get caught in it. Don’t worry about this, it’s normal.