What Causes Water-Based Paint to Discolour?

By Mike Gregory

 

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 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 oil as well. Paints such as Crown Fastflow and Johnstone’s Aqua for example, but there are several others. There are benefits in 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. The problem is, these paints aren’t marketed as “hybrids”, they’re sold as “water-based” and because of the oil content, they will still turn yellow over time.

 

 

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.

 

 

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What Causes Water-Based Paint to Discolour?