The Bail-Top Jar: A Wire Yoke, an Eccentric Lever and the Air's Own Push

"This invention relates to improvements on devices for holding the covers of jars or other vessels tightly to their places and permitting their ready removal and replacement". The lever's end enters an ear on the neckband "so as to obtain a greater contact-surface with the body of the jar than is obtained where the end of the lever is merely fitted through a loop or eye formed wholly or in part by bends in the body of the neck-wire itself. I have found that where the lever bears simply on the neck-wire during the strain of locking, at which time the lever exercises considerable power in closing the cover, jars that are not of perfect construction are very liable to break, as the strain comes against two tangential contact-faces on the head of the jar only, whereas with my improvement applied even inferior jars can be securely closed and will be protected against breakage by the closing action of the lever."

Check the jar's rubber ring is soft and uncracked. Warm the jar with hot tap water first so it does not crack, then fill it with water at about 85 C, checked with a kitchen thermometer, to 1 cm below the rim. Wear oven gloves. Put the lid on, swing the bail over it and press the lever down past its centre. Let it cool to room temperature. Then lift the lever: the lid should stay down on its own, held by the air, until you pull the ring's tab and hear the air rush in. Try again filling at 60 C and compare how hard the lid holds.

**Henry W. Putnam** of Bennington, Vermont, filed US 256,857 on 10 February 1882; it is dated 25 April 1882. The cover is not joined to the bail or lever, so it can be used without them. **Honest limits.** Water's saturation pressures are standard values; the lid size is an example, and the calculation assumes the headspace is sealed at the filling temperature. It is a seal test, not a food-preserving recipe.