Homemade Balloon style Airlock:

homemade airlock for winemaking
Poke the straw into the mouth of the pricked balloon (tape it around the straw if it’s loose) – when gases rise from the wine they will fill the balloon until the hole is opened by the expansion of the balloon. The balloon then continues to “stand up” until fermentation ends and the balloon “flops over” again signalling that it has done.