Pink Staining — What Is It & How Do I Prevent It?

Have you ever seen those not-so-subtle neon pink stains that plague marine upholstery vinyl from time to time? In the world of boating, we call this issue “pink staining” or simply “pinking.” In this blog, we’ll explain the two different types of pink stains you’ll find on marine vinyl and how to prevent pink staining from occurring in the first place.

What Is Pink Staining?

While there is much argument about what pink staining is, we’ve got a definitive answer. Pink staining is caused by a specific type of bacteria called streptoverticillium reticulum. These bacteria are quite common and no threat to you. According to David Kraft, Vice President of Gestalt Scientific, a leader in fighting the battle on pink staining, these bacteria exist in freshwater such as rivers, lakes and streams. If you go swimming, if you hose off your boat, or even if your boat gets rained on, they can make their way into your vinyl via the holes in the stitching. Kraft stated that, "We see pink staining on about 5% of boats in the Pacific Northwest. We also see a majority of it in the East Coast and places like Florida, North and South Carolina, Alabama, Maine, Michigan, Wisconsin and even parts of Canada such as Ontario and Quebec."

Essentially these bacteria produce a digestive by-product, a pink dye, that is soluble in plasticizers, a primary ingredient in vinyl-coated products. This pink dye will stain any vinyl-coated fabric it comes into contact with, wreaking havoc on your boat. Once you are seeing the pink dye, it's likely the bacteria have already died, but not before leaving you with an unsightly parting gift.

Bacterial pinking on boat vinyl. Photo provided by Gestalt Scientific.

How Do I Prevent Pink Staining?

Pink staining can be a boating misfortune, but it’s possible to prevent it before it ever occurs. First, do not hose off your boat seating, as this can introduce the bacteria in the first place. Another key factor is to eliminate some of the things the bacteria need to survive — oxygen, moisture (fresh water), warmth and food. Of all these, the easiest to eradicate are a food source and moisture. The bacteria feed on the chemical para-aminobenzoic acid (PABA) found in some sunscreens as well as sloughed-off human skin cells.

To cut off the food supply and moisture, thoroughly clean your exterior vinyl after each boat trip by wiping all of it down with a damp (not soaking wet) cloth. It also helps to refrain from using sunscreens containing PABA. Avoid letting the cushions get completely soaked with water and don’t leave damp items on your boat upholstery, such as wet towels or swimsuits. The trick is to keep things clean and dry as much as possible because these bacteria need moisture most of all, according to David Kraft.

If you’re planning to create your own exterior boat cushions, choose a foam that will resist bacteria, like our CushionRite® Standard Antimicrobial Foam. Next, select a vinyl fabric that is ASTM E1428 certified; this ensures it has undergone pink stain testing and passed. All Naugahyde® vinyl fabrics available at Sailrite® (Nauga Soft, Naugahyde All American and Naugahyde Universal) are certified to resist pink staining. Naugahyde All American and Universal are ideal choices for marine vinyl applications. You can also choose to use EverSoft™ Indoor/Outdoor upholstery vinyl, as this fabric boasts a three-year limited product warranty to ensure its performance. The key is to choose a vinyl that is easy to clean and will repel water as much as possible, as this will help to inhibit bacterial growth.

What About Chemical Pinking?

Although bacterial pinking is the most common type of pink staining, chemical pinking is another possibility for the presence of stains on your boat, but only under certain conditions. David Kraft explained that chemical pinking is caused by excessive heat, which causes the glue in your vinyl to melt — thus leading to a pink or red color on the surface of the material. Essentially, when another material, such as a boat cover, is left in contact with vinyl upholstery and then exposed to excessive heat and lack of air, the result is chemical pinking. While bacterial pinking is very blotchy in appearance, chemical pinking will look more like a pink smear. Chemical pinking is a much more rare occurrence than bacterial pinking and usually occurs in more arid climates such as Texas, Arizona, California and Nevada where there is little humidity to cool the air.

The simplest way to prevent chemical pinking is to create a barrier for airflow between your boat seating and your boat cover, especially if you’re in a hot climate. An easy fix is to put a towel over the top of your vinyl seating between your seats and your boat cover, focusing on the areas where your cover comes into direct contact with the vinyl (such as the corners). It can be difficult to remove this type of pinking once it’s occurred. Although Kraft suggested that, "Sun will fade away some, if not all, of the visual effects of chemical pinking, however, it's important to note that it will always reappear once the boat is in a dark place for more than 3-4 days or a cover is placed back over the seats. In other words, whenever the boat is removed from sunlight for more than a couple days, the visual effects of chemical pinking will always return, without exception.” To permanently remove chemical pinking, your next plan of action would be to replace the vinyl.

Chemical pinking (also called false pinking) on boat seats. Photo provided by Gestalt Scientific.

Wrapping Up

We hope you’ve learned a lot about pink staining and how to prevent it. When it comes to creating your own exterior boat cushions, Sailrite is your one-stop shop for all things boating! From high-quality vinyl fabrics and foam to needles and thread, we’ll have you well on your way to crafting your own custom cushions in no time. Not sure what type of foam or fabric you need? We have foam sample boxes and fabric samples available so you can get a better idea of the options available. If you have any other questions or concerns, our helpful customer support team is happy to assist you. Just give us a call, shoot us an email, or chat with us on our website. And for more information about Gestalt Scientific and their fight against pinking, visit their website.

Footnote:
This blog was updated in December 2019 to include mention of EverSoft vinyl. It was updated again in April 2024 to remove mention of discontinued Sunbrella Horizon vinyl.