It's happened twice in a row now. Can anyone recommend how to prevent it. I've had years of no fermenting problems, now twice in a row. I'm sad.
Eeeew, it looks so for me. Harmless but untasty. Scum it off carefully, and taste the brine - if it tastes OK or off.
Typically I avoid kahm by using 2% salt in the ferment, and an airtight lid. The lid doesn't need to be fancy, just to let the carbon dioxide out without the oxygen back in; for me it's typically just a plastic bag filled with water over the ferment (inside the jar), it also works wonders against mould (as the pieces of cabbage can't touch air, there's no solid surface for it to start developing).
Damn. I used 2% and one of those swing top lids which is self burping. What I will say is that this time, and maybe the last time my weights weren't under liquid.
If it's happened twice in a row you may want to sterilize/sanitize your container and fermentation weights. There's a chance some of it hung around from last time. Although kahm yeast just hangs out in the air so I'm not sure if it'll have a huge effect.
Yeah you're probably right. I've got some of those tablets from doing cider before.