What Causes Water-Based Paint to Discolour?

Updated May 9, 2024 | Posted Nov 21, 2020 | Professional insight, Product Advice | 0 comments

It’s no secret that modern day oil-based paint such as gloss, satinwood and eggshell will start to discolour and turn yellow fairly quickly do to the alkyd oil used in the paint, and EU restrictions on VOCs.

For this reason, a lot more people seem to be using water-based paint instead. However, water-based gloss, satinwood and eggshell isn’t perfect, and you can have similar issues. But what causes water-based paint to discolour? I’m going to explain the 3 main issues.


Hybrid Paints, Disguised as Water-Based


Hybrid paints are primarily water-based but do contain some alkyd oil as well. Paints such as Crown Fastflow, Johnstone’s Aqua, or Teknos Futura for example, but there are several others.

There are benefits to using hybrid paints and I’m not knocking it as a product. Think of it as a compromise between oil and water-based. For example, they are more durable than water-based paints, but not quite as durable as oil-based. They leave a better finish than water-based, but not quite as good as oil-based. They WILL discolour over time, but not as quickly as oil.


The problem is these paints are normally labelled as “water-based”. So, if you’re looking at yellowed woodwork in your home which you thought you’d painted with water-based satinwood, the chances are you used a hybrid.


Stains Bleeding Through the Paint


An issue with water-based paint is it doesn’t have the same stain blocking capabilities as oil-based. This means that any nasties on the surface you are painting can easily bleed through and effect your lovely paint finish. So, if for example you’re painting skirting boards which have been previously coated in wood stain, you may get tannins bleeding through. Or, if your skirting has been painted in oil-based paint which has yellowed, the oil from the previous paint may still come through over time.

Funnily enough, the solution is to use a full coat of oil-based undercoat or Zinsser Cover Stain which is also oil-based. Just make sure any oil-based paint has had chance to fully dry before applying a water-based product.


Sunlight Causing Paint to Fade


Seems obvious, but people tend to overlook this so it’s worth mentioning. Paint which is exposed to sunlight for prolonged periods of time will start to fade. Not so much white paint, but any tinted water-based satinwood, gloss or eggshell definitely will. The UV breaks down the pigment in your paint.


Final Thoughts


It’s strange isn’t it; You’d think there would be less problems with water-based paints discolouring. Using good-quality, fully water-based paints will always help with longevity. However, you still need to be conscious that a painted surface is never going to last forever. Whether it’s the polymer that breaks down, the alkyd that turns yellow, or the pigments that fade, you’re always going to need to repaint every few years.

Blog written by Mike Gregory – Professional Painter, Decorator and Blogger

Updated May 9, 2024 | Posted Nov 21, 2020 | 0 comments

About the Author

About the Author

Mike Cupit has been in the decorating industry since 2002 and has mostly worked as a Trade Decorator in the domestic sector (peoples’ homes). Self-proclaimed “product geek”, Mike has a passion for paint and decorating tools. Mike now spends most of his time testing paint products and tools, comparing them to similar products on the market, and blogging about the industry in general.


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