Why Do Oil Paintings Turn Yellow?

Why Do Oil Paintings Turn YellowEveryone has seen it at one point or another. A normally vibrant painting gets a touch of yellow to it and while this gives it an ‘antique’ look, it can also mess a bit with the color scheme. So, why do oil paintings turn yellow? There are a few reasons why oil paintings may turn yellow over time. One form of yellowing called ‘dark yellowing’ occurs when paintings are stored in dim or dark areas and this has to do with molecules called ‘chromophores’, though proper light will reverse the process. With older paintings, sometimes it’s bits of old varnish still stuck in the painting as well.

Today I’ll tell you a little more about yellowing and it’s causes so that you’ll have a good idea of why it’s happening and what you might able to do if yellowing occurs in your paintings.

Let’s talk about the not-so-wonderful world of yellowing!

Why do old paintings turn yellow?Why do old paintings turn yellow

With older paintings, an interesting study which was done by Dutch researchers found that old bits of varnish were getting trapped in paintings during their cleaning process. The problem with this is that those old varnishes were sometimes made of resins extracted from trees which were selected to give the painting a bit of extra shine or to bring out certain colors. Over time, those varnishes would start becoming less clear and more yellow.

These varnishes also make the cleaning process much more difficult. Even when you put a modern varnish on your painting, you want to identify the type of varnish used so that you may effectively remove it when you want to clean that painting. With tree resins and other early-era varnishes, you can’t simply apply a little acetone or alcohol and expect to get everything – their chemical composition is quite different from what we use today. Thus, particles of the varnish get trapped in the painting and over time it starts to show.

While another cleaning process and analysis might be able to deal with those particles, it’s really going to be a ‘case by case’ thing as it may have chemically reacted or otherwise bonded with the paint. In many cases, the yellowing might well be there to stay.

Why did my white oil paint turn yellow?

Why did my white oil paint turn yellowOne reason that white oil paint can turn yellow is exposure to too much moisture. In a case like that, unfortunately, there is not a lot that you can do. The most common reason for yellowing of white paint, however, has to do with chromophores.

Chromophores is a somewhat generate term for ‘color molecules’ which get produced when paint is stored in the dark or in insufficient light for too long. They can also build up while you are painting if the light is not strong enough in your painting area. It’s somewhat of a ‘known issue’ with oil paints, but there is a bit of light on the horizon in regards to this issue.

Exposure to a sufficient light source will actually break those chromophores down and may reverse the process. Try taking your painting and moving it to a brighter area so that the chromophores can break down naturally. You should start seeing the painting lightening up over time as they break down.

How do you keep white oil-based paint from turning yellow?How do you keep white oil-based paint from turning yellow?

As far as keeping your oil paintings from turning yellow, there are a few habits which you can get into that can minimize this possibility. Here are a few tips that should help:

  • Avoid moisture – Moisture can definitely cause yellowing over time, with no other recourse at that point beyond essentially sanding down the area, repriming it, and repainting it. Keep your painting away from areas which are humid and this will help to minimize their chances of yellowing.
  • Sufficient light – Always paint in areas where the light is bright to avoid the generation of chromophores. Painting in dim light isn’t good for your eyes anyways, so that shouldn’t be a problem. Also, try not to store them in dark areas for a long time. If you have to, don’t panic – light should fix that yellowing with a little time and patience.
  • Avoid smoke or cooking areas – Never hang a painting over the fireplace or in the kitchen. The heat and smoke in these areas can cause paintings to yellow over time. It’s a slow process, but it will happen, so keep your paintings away from these areas.

Some closing comments on oil paintings and yellowing

As you can see, there are a few reasons why yellowing can occur but in many cases it’s something that can be fixed. Yellowing may occur in antique paintings due to trapped fragments of tree resin varnish and in more modern works it is often caused by insufficient light causing the generation of chromophores. Finally, moisture can cause it too, so you want to keep your paintings somewhere that it’s going to be very dry.

Before I go, I’ve got a 3rd party link that can tell you a little more about chromophores and ‘dark yellowing’ just in case you are interested. Just click here and you can check it out for yourself!