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Have you ever seen strange pink splotches on your outdoor furniture or cushions? You try recalling how they got there, but nothing comes to mind. Is it a set-in wine stain? Paint perhaps?

It could actually be the by-product of a specific type of bacteria. Said derivate is known in the outdoor industry as “pink stain.” It’s completely harmless to humans—so no need to worry—but you may not think your furniture looks so pretty in pink. Keep reading to learn more about pink stain, how to prevent it, and how to remove it from your outdoor furniture.

What is Pink Stain?

Pink stain on the seams of white boat seats.

Photo Credit: boatingmag.com

Pink stain, also called “pinking,” is the insoluble digestive by-product of Streptoverticillium reticulum, a common and completely benign bacteria. Found in rivers, streams, lakes, and other freshwater spots, these bacteria feed on dead leaves, algae, food scraps, and other organic matter. This rose-tinted waste shows up after the bacteria die—a pink parting gift, so to speak. It won’t hurt you, but it might give you the ick.

Surfaces Affected by Pink Stain

Pinking mostly occurs in damp environments like boats, piers, garden decor, and other areas exposed to continuous excess moisture. However, patio furniture doesn’t commonly experience this because homeowners typically keep these items on patios, decks, and other dry, ventilated areas with sun exposure.

Pink staining is even less likely to occur on outdoor furniture built from high-density polyethylene (HDPE). Manufacturers prize HDPE plastic for its high resistance to microbial growth because it's non-porous, water-resistant, UV-resistant, and chemically inert. It basically lacks just about everything bacteria need to survive.

A POLYWOOD Quattro Folding Adirondack in White sits by a pool ledge with a glass of red wine on the armrest.

Featured: Quattro Folding Adirondack in White

That’s not to say that bacterial growth is impossible on HDPE. Microbes are bound to appear if conditions are right and patio furniture is left in a damp and dirty state long enough.

How to Remove Pink Staining

A hand uses a wooden-handled brush to scrub soapy water onto Slate Grey HDPE lumber.

Follow these steps to rid your furniture of pesky pink stains.*

Supplies Needed

  • Mild dish soap
  • Bucket
  • Soft-bristle brush
  • (Optional) liquid bleach
  • (Optional) towel

Instructions

1. First, mix soap and warm water in the bucket.
2. Next, scrub the soapy solution over all surfaces with the soft-bristle brush.
3. Then, give your furniture a rinse with clean water and let it air-dry in a sunny, well-ventilated area.

Optional Steps for Stubborn Stains 

4. If the pinking persists, make a diluted solution of one part bleach to nine parts water.
5. After that, apply the mixture to the furniture, letting it sit for 10 minutes.
6. Finally, rinse all surfaces with clean water and towel-dry your furniture to ensure all moisture is removed.

An Alternative Cleaning Method

If you prefer to avoid bleach, you can try white vinegar instead. To start, simply mix equal parts water and vinegar in a spray bottle and then spritz your furniture frames from top to bottom. Next, let the solution sit for 15 minutes. After that, scrub all surfaces with a soft-bristle brush, and finally, let your furniture air-dry.

*NOTES: 

  • Always spot-test cleaning solutions in small, unnoticeable areas first to ensure they don’t damage your furniture material.
  • Wear gloves and work in a ventilated area when using bleach or other harsh chemicals.
  • Never mix bleach with vinegar, as it produces a toxic chlorine gas that’s harmful if inhaled.

Prevent Pinking on Patio Furniture

Here are our tips to keep pink stains off outdoor furniture.

  • Clean your furniture regularly.
  • Keep all surfaces dry and free of debris.
  • Place furniture in sunny, well-ventilated spaces.
  • Don’t let water pool or stagnate on seats and tables.
  • Cover or store your furniture when it's not in use.

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FAQs

Is pink stain the same as pink mold?

Pink stain is caused by Streptoverticillium reticulum, whereas pink mold comes from different species of bacteria called Serratia marcescens and Aureobasidium pullulans. Pink mold is mostly seen in bathrooms, staining shower floors, bathtubs, and faucets. 

Though not nearly as dangerous as black mold, pink mold can pose health risks to those with weakened immune systems. Serratia marcescens and Aureobasidium pullulans thrive in moist environments, feeding on minerals, fatty deposits, and soap residue. Keeping your bathroom clean and dry will hold these bacteria at bay.

Why do some bacteria stain pink?

Some bacteria stain pink because the pigmented metabolites (aka colored by-products) they produce as they grow are pink. The hue of a metabolite is determined by the molecule’s chemical structure and environmental factors like pH, oxygen levels, and temperature. Metabolites can be a variety of colors, including pink, red, purple, blue, green, and many other shades.