
By pressing the ends of a can with fingers, it will detect flippers and springers and soft and hard swells. Springer - a can with one end permanently bulged. When sufficient pressure is applied to this end, it will flip in, but the other end will flip out.
Flipper is a can that normally appears flat; A slight distension of one end of the container where outside pressure will return the end to a normal position but will cause the other end to flip out. Flippers result from a lack of vacuum.
This condition is actually the beginning of a hydrogen swelling or due to an insufficient exhaustion or over-filling beyond the capacity of the can. Flippers or springers are most frequently caused by inadequacies of vacuum and headspace, and only rarely by microbial spoilage.
Can defect: springers and flippers