The plastic sandwich bag is a fixture of modern life, used daily for everything from school lunches to storing leftovers. Its simple design, a thin film of polyethylene, belies a complex and recent history rooted in mid-20th-century chemical innovation. The origins of this ubiquitous item reveal a rapid shift in food preservation practices, moving from traditional wraps to highly engineered plastic polymers. This evolution transformed how food was packaged, stored, and transported.
Food Storage Before Plastic
Before the development of cheap, mass-produced plastic, people relied on a variety of materials for food storage. Wax paper was a common choice for wrapping sandwiches and baked goods, using a thin coating of wax for moisture resistance. This paper was also breathable, helping prevent items from becoming overly moist or drying out during short-term storage.
Cloth bags, glass jars, and tin cans were widely used for longer-term preservation and transport. Early aluminum foil provided another barrier option, but it was not breathable and was generally more expensive than paper products. These older methods lacked the convenient, transparent, and water-tight seal that modern plastic film would eventually offer.
The Invention of the Plastic Bag
The foundation for the plastic bag was laid in 1933 with the accidental creation of polyethylene, the polymer that forms the basis of the modern bag. Initially, this flexible, low-density plastic was used for industrial and military purposes, but its potential for packaging was soon recognized. Commercial plastic food storage products began appearing in the late 1950s and early 1960s, marketed for general freezer and refrigerator use.
These initial food bags were simple, open-ended polyethylene sacks that required a twist tie or knot to close. A precursor to the modern reclosable system was a plastic slide fastener, patented in 1951, first applied to products like pencil cases and document folders. The transition to a dedicated food storage bag was driven by the desire for a better, more secure method of preservation.
Evolution to the Modern Sandwich Bag
The development of the “press-and-seal” closure mechanism was the final step that led to the sandwich bag recognizable today. This technology evolved from a slider-based plastic zipper into a system of interlocking, extruded plastic grooves. The key innovation was a manufacturing process that allowed the zipper profile to be integrated directly into the polyethylene film, significantly reducing production costs.
By 1961, a company called Minigrip began marketing this integral zipper format, primarily to industrial clients. Dow Chemical Company secured the exclusive rights to sell the technology to the consumer grocery market around 1964. This partnership led to the launch of the Ziploc brand, which was widely marketed starting in 1968. That same year, the smaller Ziploc Sandwich Bag was introduced, specifically sized for daily lunch-packing and snack storage.