Milk Jugs

J. Metz

Why don’t we buy our milk in glass jars anymore?

Since 1976, plastics have been the most used material in the United States.  Plastics have taken over the packing industry because of the many benefits to replacing the glass containers.  One advantage of plastic jars over glass jars is the strength of the package.  When a plastic jug is dropped there is a greater chance that it will not bust all over the floor.  But when a jar is dropped the glass shatters on contact and there is reason to cry over spilled milk.  Plastics are used to keep many products safe because they are so tough.  Another advantage to using plastic jars is how light this material is.  Glass used for jars are about 2.6 times the density of HDPE (high density polyethylene) used in plastic milk jugs.  In addition to glass being heavier than HDPE plastic, more glass is required for the same container made of plastic to increase toughness.  If more glass isn’t used then the jar will break way too easy.  It requires 1/2 pound of plastic to package 1 gallon of milk compared to 3 pounds of glass.  Therefore less material is needed to package the same amount of milk.  This means companies can save money because they can load more milk into a truck to ship across America.  This conversion, from glass to plastic jugs, makes customers happy because they don’t have to carry an extra 3 pounds of glass to the car.  This is why we don’t see glass milk jars in the grocery store anymore.