Is there such thing as a spunding valve for a demijohn or swing-top bottle?
I want to make elderflower champagne for the second time. Last year it was fermented in plastic bottles, and one of them exploded. I figured there must be some sort of equivalent of an airlock that releases above a certain pressure, and thus I discovered that spunding valves are a thing.
However, it seems that spunding valves are made only for kegs, and specialised pressurised fermentation vessles.
Does such a thing exist for glass swing-top bottles or demijohns? Is this a silly question, and am I missing a reason why this would be non-sensical?
Apologies if this is daft. I'm totally new to this, having made elderflower champagne once before, and nettle 'beer' a few weeks ago.