Interior View of a Plastic Bag (2023)Science History Institute
This is an ordinary plastic bag from a grocery store. We don’t know anything about the history of this particular bag. But you can learn a lot about plastic—and the society that makes it—by closely observing this bag through a historical lens.
Look at the shape
The plastics industry calls this a T-shirt bag since it looks like a sleeveless, scoop-neck shirt.
The design was mass produced by Swedish plastics manufacturer Celloplast during the 1960s. Now it’s widely used in grocery stores. Other common shapes of plastic bags include zippies, gussets, doypacks, and flat polys.
3/4 View of a Plastic Bag (2023)Science History Institute
Feel the texture
Most of the bag feels slick and smooth. This bag is made from a tube of thin polyethylene film. Polyethylene is formed when molecules of ethylene gas bond together in long chains, a process called polymerization.
Side chains branching off of the main strand affect the material’s density. Low density polyethylene is a stretchy, clear plastic used in cling wrap and vegetable packaging. This bag is made of high density polyethylene (HDPE) that better resists punctures and tears.
View of Weld on a Plastic Bag (2023)Science History Institute
Touch the sides and seams
In 1959 Swedish engineer Sten Gustaf Thulin patented an ingenious system of folds and welds that make the bag strong. The bag costs pennies to make. It can carry more than 1,000 times its own weight.
Warning Label on a Plastic Bag (2023)Science History Institute
Heed the warning
During the late 1950s dry cleaners began returning clothes to customers in polyethylene sacks. But by 1959, the clingy film bags had been linked to the accidental deaths of 80 children and 17 adult suicides. Dozens of cities proposed to ban the bags.
Manufacturers responded with a national campaign to educate consumers about the dangers of polyethylene sacks. The plastics industry adopted standards to make bags thicker and less clingy. Today five U.S. states and multiple national governments require printed warning labels.
Look for a maker’s mark
Bill Seanor at Mobil Oil pioneered the commercial development of the T-shirt bag in the 1970s. But Mobil was committed to using low density polyethylene that stretched and tore. Seanor and his colleagues established Vanguard Plastics to make bags of HDPE.
Plastic grocery bags weren’t popular with consumers when introduced in the 1970s. Customers disliked how the bags fell over, unlike stiffer paper bags. Clerks licked their hands to open the bags, repulsing some customers. Bag makers tried to persuade customers to like them.
Is there a torn flap on the bag’s mouth?
One way to help clerks open bags and reduce customer gross-outs was to design a system that pulls open the next bag when the previous one is removed. Sunoco patented the “self-opening polyethylene bag stack” in 1992. Other companies patented their own methods.
Kroger Logo on a Plastic Bag (2023)Science History Institute
Who gave away this bag?
Retail companies didn’t immediately embrace plastic bags either. But they were much cheaper than paper bags. After large grocery chains Kroger and Safeway adopted plastic in 1982, the T-shirt bag soon became ubiquitous.
Aged Plastic Bag Floating in a Wild Sea (2015-03-12) by Paolo Gamba (Flickr User Abukij)Science History Institute
Ubiquity creates problems
By 2000 the average American received 300 T-shirt bags a year. These bags don’t biodegrade. They only break into ever smaller pieces of plastic.
Look for a recycling symbol
Public concern about waste threatened the single use plastic market. In 1988 the Plastics Industry Association developed the Resin Identification Code to promote plastic recycling. The numbers from 1 to 7 correspond to different plastics. #2 HDPE means high density polyethylene.
During the 1990s plastic makers urged regulators to mandate the use of resin codes. Consumers began to separate and sort their plastic waste. This gave the impression that plastic was widely recycled. But today, less than 10% of plastic is actually recycled.
White Plastic Bag (2016-05-03) by Lasse Erkola and @laserkolaScience History Institute
Bags are particularly troublesome
Lightweight and aerodynamic, bags flutter out of bins and tangle up conveyor belts in recycling plants. In 2000, Mumbai, India, banned plastic bags. More recently, cities like Philadelphia have restricted all single-use bags, including paper bags not made with recycled material.
Messaging on a Plastic Bag to Encourage Recycling (2023)Science History Institute
Where should this bag go?
In the face of a growing number of bans, the plastic industry once again promoted consumer education and recycling. For instance, Industry supported a 2005 California law that pre-empted city taxes on single use plastic bags while requiring grocery stores to offer recycling.
Is this adequate?
Despite labels and store-based collection, plastic bags remain a major source of unrecycled waste. What do you see in the plastic bag’s future?