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What Are the Black Spots on the Sidewalk? (A Sticky Issue)

What Are the Black Spots on the Sidewalk? (A Sticky Issue)

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If you tend to look down a lot while walking, you’ve probably asked yourself this question at least once: what are the black spots on the sidewalk?

The most widely accepted explanation for those dark patches is that they’re dried pieces of gum that have been squashed into the concrete or brick surface.

How can a measly piece of gum possibly cause a spot like that, and what can we do about it?

That’s what we set out to find by looking at how improvement districts and cleaning companies handle the issue. We’ll also see what other theories people are coming up with to explain the black blobs’ origins.

How Does Squashed Gum Leave Black Spots on Sidewalks?

It’s hard to picture how something as simple as gum could be the culprit behind those ugly splotches, but let’s break things down a bit:

  1. Someone decides to spit out their gum on the street.
  2. It doesn’t get kicked over or washed away by the rain.
  3. A few people squash that blob right into the concrete until it sticks in place.
  4. Soon, the sticky surface starts collecting dirt from the air and people’s shoes.
  5. Then, the sun takes over things from here and sucks all the moisture out of that gum.

By now, it’s no longer a squishy pink gum but rather a black hardened stain on the sidewalk.

Is There a Fix for Gum Spots on Sidewalks?

While these gum spots aren’t particularly dangerous, they can be quite an eyesore.

Some people in hectic cities (looking at you, New York) just get used to the sight and manage to tune it out while walking down the street. Others find it irritating, though.

Unfortunately, until people stop spitting their gum onto the sidewalk, there’s no way to nip this issue in the bud. That said, there are a few ways that we can tackle those ugly black blobs.

Here are our favorite five tactics:

1 – Putting in Some Elbow Grease

The most obvious approach here would be scraping those blobs away with a razor, a putty knife, or a wire brush.

That approach could work if you only want to clean up a few spots in front of your property. Of course, it would be a tedious task if you need to cover a larger area.

That’s why some districts powerwash the sidewalks.

The catch here is that, more often than not, the sidewalks need to be completely empty of pedestrians to do that. Even if the city districts pick a time after midnight when the streets are empty, the cleaning crew still needs to ask homeless people off the sidewalk.

There are alternatives to the traditional power washer, though.

For one, there’s the GumBusters cleaning machine that combines both solvent and low-pressure steam systems. However, the cost is usually too steep to be implemented city-wide.

2 – Regulating the Chewing Gum Market

Instead of trying to clean up those pesky spots, some governments have decided to regulate chewing gum. Take, for instance, how Singapore banned importing gum.

No mass-sold gum means no squashed blotches to scrape or steam. Problem solved.

If you’ve ever been to Disneyland, you’ll probably notice a similar regulation. Although gum isn’t actually banned there, it’s not sold in any souvenir shop at the resort.

3 – Switching to Non-Stick Gum Base

It sounds a bit counterintuitive to make non-sticky gum, but that’s exactly what Bristol University and Revolymer did in 2010 with the Rev7 gum.

The main idea behind the product is that switching the base to something less sticky and more biodegradable makes the removal process much easier. Being water soluble is also a major plus—rain will take care of the clean-up!

In fact, the testing shows that the new and improved base can disintegrate from sidewalks in around 6 months with nothing more than water and some agitation, leaving behind fine powder. Let’s hope this concept takes over for the sake of our streets!

4 – Turning the Residue Into Art

While some people tune the black spots out of their vision and others try to steam it out of the sidewalk, a third portion chooses to turn it into something beautiful.

So, don’t be surprised if you’re walking down the street in London and spot a colorful patch on the ground—that’s probably one of Ben Wilson’s miniature gum paintings!

Ben Wilson is an artist that turns those squashed gums into artwork inspired by the community. Of course, the process is meticulous, with blowtorching to soften the residue, adding layers of lacquer, and painting with the tiniest brushes you’ve ever seen.

You don’t have to go all in like Wilson does, though.

Try chalking a constellation using the blobs as guidelines. You can even connect the dots to spell out a word and have fun with it!

5 – Phasing It Out

We’re not talking about phasing out gum—although younger generations already seem to steer away from chewing gum for some reason.

Instead, we mean phasing out the whole concept of littering, from chewed bubble gum to cigarette butts. After all, some sources estimate that 80–90% of all chewed gum isn’t disposed of properly!

Some authorities combat this issue with hefty fines, but that isn’t always enough. Others opt for awareness campaigns to show people how a simple choice to avoid littering can affect the city’s aesthetic.

Odds are, we need a bit of both tactics to see significant results.

Could It Be Anything Other Than Discarded Gum?

Before we get accused of being too harsh on bubble gum, we also want to point out that there could be other culprits behind black sidewalk stains, including:

  • Mold
  • Cigarette tar or ash
  • Lichen
  • Tree sap stains
  • Calcium chloride concrete additives
  • Fertilizer pellet stains

One way to tell all those spots apart from gum is to consider how flat they are.

Gum leaves a blob that will still be slightly raised over the brick or concrete, even after it’s squashed. Meanwhile, sap usually just stains the sidewalk without adding any mass to the surface.

Plus, if you try to scrape the spot, you’ll be able to tell right away that it’s gum. Some people even say they can smell fresh gum once they slice the hardened surface!

Final Thoughts

Lichen growths, tree sap, and even fertilizer pellets can leave behind black stains on concrete and brick flooring. However, dried, dirty gum remains the most obvious explanation, especially if you live in a busy city.

Next time your gum loses its flavor, remember to put it back in the wrapper and throw it in a trash can instead of spitting it on the sidewalk!

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