of Note - Gum Wall

For all the planning, attention to detail and careful material selection that go into design and construction of a building, there is no way to ensure it will be used or treated as intended.

Once upon a time, in Post Alley under the famous Pike Place Market in Seattle, someone stuck a piece of chewed gum on the side of a brick building. Twenty-some years and thousands of pieces of chewed gum later, the Gum Wall has become a tourist destination in its own right.

In November, the City decided it was time to clear the layers for aesthetic reasons as well as to protect the brick and mortar from damage or deterioration resulting from gum buildup. More than a ton was removed!

The Belden Brick Company notes that chemicals in chewing gum (glycerin, polyvinyl acetate, calcium phosphates and glucose) may disintegrate concrete over a short period of time, but chemical-resistant brick slows down this process. Each ingredient has a pH level between 3.0 to 10.0, all within the safe zone of brick. Culprits may be artificial sweeteners used in gum flavoring and human saliva on gum when it is stuck on the wall. Both sweeteners and saliva contain trace amounts (50 parts per million or less) of fluorides.

These are not harmful to the integrity of brick, but the collective mass of gum and leaching effect of these seemingly harmless chemicals being absorbed over an extended period of time may potentially cause problems. Trace amounts of chemicals present in each piece of gum could combine with other gum plastered onto the wall to produce detrimental amounts of harmful chemicals that could cause staining and/or slight deterioration of mortar.

Whether the gum is affecting the wall will remain hard to determine. Within hours, people began adorning the wall with chewed gum again. The good news is that brick can resist most harmful chemicals, even gum!


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