I’m new to win making and didn’t heed the warnings of topping off a bottle!! My small bottle of extra wine oxidized . Luckily my gallon is ok!! Lesson learned!! Always top off the bottle!! I’m tossing it out! See the brown ring on the rim of the wine? See the difference in color? Airlock and bung was tight and holding. Just too much headspace I guess. This was after 1 3/4 months setting.