How to Date Historical Cans
Tin can technology changed through time to improve food safety and prevent failure. These technological changes can help collectors to date their cans. The canning industry began in the early 1800s. Initially, tin cans were cut, shaped, and soldered by hand, but air leaks made early cans prone to food spoilage. The 1840s ushered in the machine-age for the canning industry, and by the turn of the 20th Century canned food safety became much more dependable. The use of poisonous lead solder for seams also disappeared in the 1900s.
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Instructions
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Dating Can Lids and Ends
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Look for a flat cap in the middle of one end with a pinhole. These are hole-in-cap cans. After filling the can through a hole in one end, a cap was hand-soldered with lead to seal the can. The pin hole, in the cap center, enabled it to be heated without rupturing to drive out air and moisture. These cans mainly date from the 1820s to the 1840s. Evaporative milk cans continued to use pinholes into the 1900s but otherwise exhibit machine-made characteristics.
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Look for machine-stamped ends. In 1847, the invention of the drop press enabled can ends to be attached by machine. Side seams on these cans are still soldered by hand.
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Look for a "key" or a narrow metal band. These are key-wind cans. In 1866, a closure mechanism that consisted of a scored band on the side or end of the can was invented. Getting to the contents required a key to "wind" open the can. By 1900, key-wind use declined dramatically, but sardine cans still use this mechanism.
Dating Can Seams
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Are the seams soldered irregularly with globular lead solder on the side and ends? These cans are hand-soldered and date prior to the late 1800s.
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Does the solder appear thin and evenly applied? These are machine-soldered cans and probably date from the late 1880s to the early 1900s. In 1888, the Max Ams Company of New York invented a machine that locks the body of the can together with double-sided seams and machine-solders them. This greatly increased food safety.
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Is the can solderless with crimped side seams? Lacking a cap and pinhole, these are likely sanitary cans. In 1904, the Sanitary Can Company began producing a completely machine-made can that is airtight, double-seamed, and requires no solder. The absence of lead solder made food safety much greater. This ushered in the modern era of mass manufacture of canned foods.
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Tips & Warnings
Paper labels were first used in the 1870s (see "Labels, Leadville and Lore;" Douglas H. Rhoades; 2005).
The first beer cans were made in the 1930s and have cone-shaped tops.
Church-key beverage cans largely date from the 1940s and 1950s.
Pull-tab beverage cans date from 1962 to the mid-1970s.
Aluminum cans date after 1960.
