07/13/2026
Ok folks. It is past that time of year again and just a reminder to take good care of your vinyl and treat with witha vinyl dressing so this doesn't happen to you. Always. If your boat sits in the sun with a cover on it. Always place white towels between the vinyl and where the cover touches it. Spray the dressing on, Place the towel and then cover the boat. This is proven advice to work for you and save your vinyl from ruin. Just ask my Friend and long term customer John Hardester
MARINE VINYL DISCOLORATION
While there is a very low frequency of marine vinyl discoloration occasions in comparison to the size of the marine market, it is a fact that boat owners and marine dealers do report discolorations and unusual colorations occurring on vinyl components.
There is not a single answer that can be given to explain vinyl discoloration but rather there are multiple mechanisms that can produce the unwanted color change on marine vinyl components. These color changes can result from complex chemical changes within the vinyl composition or the colorations can be due to the enzymes and by products from micro-organisms such as fungi -- molds, mildew -- and from a specific form of bacterium.
A vinyl’s composition is the key to a stable product that remains free from chemical changes and the resultant undesired discolorations. A vinyl product not optimally formulated against its environmental stress factors and ageing can chemically degrade and produce an array of shapes from small discolored spots, large splotchy areas to a more uniform solid appearance.
One highly researched and documented type of vinyl chemical change is chlorine loss from the vinyl structure. This vinyl structure change is known as dehydrochlorination.
The dehydrochlorination process is primarily driven by thermal decomposition; and with increasing temperature the speed of degradation change is accelerated. This process typically results in yellow to brown to black discolorations and these color changes are permanent. While marine covers are not the root cause of the vinyl degradation, the covers do play an assisting role by enabling temperature and moisture build-up in the vinyl’s environment. Elevated temperatures, UV radiation and moisture are some stress factors that impact a vinyl’s stability. Marine covers constructed with darker colored materials will typically develop a higher temperature profile compared with light shade colors. Hence, more vinyl thermal discoloration issues may be present with the dark shade covers.
Other vinyl chemical changes and color formation can involves the vinyl’s additives which impart specific performance characteristics to the vinyl. Attributes such as hardness, flexibility, softness, luster, color, heat stability, UV protection and flame re**rdant performance, to name a few --are achieved by incorporating specific chemical additives in the vinyl formulation. Optimized formulations can re**rd degradation changes; whereas, non-optimized formulations can contribute to degradation and color formation. Reversible and non-reversible pink, purple and yellow to brown and even black discolorations may result depending on the reaction and the resultant chemical structure.
Specific types of vinyl changes produce a reversible pink chromophore (or colorant). A characteristic of this pink color structure is that it is easily photo-oxidized by the sun’s energy and converted to a colorless structure. A case history of this reaction is that the boat owner removes the cover from the boat and observes pink color on the vinyl. As the pink is exposed to the sun light the pinking starts to fade away. And given sufficient sun energy exposure the pink will completely disappear. However, this pinking phenomenon is very likely to reappear on the vinyl when the protective cover is put back on the boat and the vinyl conditions are conducive to regeneration of the pink chromophore. (see picture below)
Another interesting situation involving reversible vinyl pinking centers around the marine cover’s light transmittance properties. A light shade Sunbrella® or SurLast® woven fabric may allow sufficient light energy to past thru the fabric to produce the photo-oxidative effect and the pink color does not form. Whereas, in the same environment a dark shade woven fabric will transmitted less light onto the vinyl and the pink color can form.
An additional proposed vinyl pinking concept involves environmental volatile organic compounds reacting with certain vinyl additives. Since this concept needs further study, Glen Raven is interested in establishing a joint study with one or more vinyl manufacturers to explore this theory in more detail.
Micro-organisms are everywhere in nature and it is not uncommon to have microbial contamination and resultant discoloration and stains on vinyl. Various colored stains can occur from mold and mildew; however, the more typical colorations are grays and browns.
(before)
(after exposure to sunlight)
These stains results from the enzymes and by-products produced by the micro-organisms. There are four components necessary for the growth of mold and mildew. The requirements are moisture, proper temperature (84 to 105 degrees F), spores and a food source. And a marine cover may provide two of the four requirements -- temperature and moisture. The mold and mildew colorations can usually be cleaned from the vinyl with a dilute chlorine bleach solution. And of course, the proper cleaning and maintenance of a boat’s vinyl and interior is of paramount importance in mitigating against mold and mildew growth. However there is a bacterium, Streptoverticullium rubrireticuli, that produces a pink coloration that is difficult to clean from substrate. The pink color is due to two red pigments excreted by this specific bacterium.
As previously stated, the root causes of vinyl color changes are not directly related to Glen Raven’s Sunbrella® or Surlast® covers. Vinyl discoloration has been reported with a wide assortment of different fabrics composed of various generic fiber types and different fabric finishes – coated, laminated, rubberized, and water repellent finishes. The bottom line is that vinyl products with various compositions interact with their environment differently. Environmental stresses impacting vinyl compositions are heat (thermal degradation), oxygen (oxidative decomposition), light (photo-degradation), ionizing radiation (radio-degradation), atmospheric contamination, moisture, or by micro-organisms and their enzymes or by products. And the result of these stresses on a PVC profile not correctly formulated is the apparition of unusual colorations, from yellow to black, from pink to purple [1].
With the above scenarios, one can appreciate the complicated issue that vinyl discoloration can present to an individual attempting to discern the root cause. However, the marine industry does not stand alone in experiencing vinyl color changes. There are many papers and references published about vinyl siding, windows, and door trim that exhibit “pinking” discoloration. “Pinking” is also documented to occur on vinyl floor tiling and on the vinyl lining inside a picnic ice chest. And many individuals have experienced a white vinyl radio cover or other vinyl devise that has yellowed and discolored with age.
References:
1. “Turning the light on unusual colorations of PVC profiles” by Isabelle Georges-Guerand, R&D Engineer, at Profiles 2001 (21st March, 2001.)
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