Originally Posted by megatrom
1.060 when yeast was pitched. Was in primary 6 days. Didn't get a gravity reading when racked (hydrometer on loan will have back tomorrow, terrible timing I know) that's my next step. Even with a stuck fermentation I've never had negative pressure before.
You only want to dryhop when fermentation is done, about a week before you bottle, so it's important to make sure fermentation is finished before racking.
In any case, the only reason for negative pressure is a change in temperature or in barometric pressure. Maybe you're getting a change in the weather? Or you put the carboy in a cooler place?