M2=H2: Y is for Yellowing

Unless you opted for custom paint colors in your new home, you very likely have some shade of white walls and white trim throughout your house. After several years, you may notice that these walls are not as fresh-looking as they used to be. They might even have a yellowish cast. This color change, called yellowing, may occur for several reasons.


ALKYD PAINT: A very durable and water-resistant paint, alkyd is often used in kitchens and bathrooms. You will notice the yellowing if the wall is seen next to something that is pure white, such as your tub/shower. To understand why the yellowing occurs, you must learn a bit about alkyd paint. All paint has two components – the color (called the pigment) and the binder. After you apply the paint, the binder dries and holds the pigment in place. While early paints had an oil binder, modern paint has either a latex binder or an alkyd binder. Latex is water-based, and alkyd is synthetic oil-based. Latex paint will not yellow. Alkyd paint yellows even more quickly in dark rooms and when ammonia is present.

WHY IT HAPPENS: If a room is dark or if it receives little natural sunlight, alkyd paint will have a chemical reaction that accelerates the yellowing. If you know in advance that a room will not get much light, considering using only latex paint in that area. Yellowing from ammonia exposure may happen from two sources. First, if you have some latex-painted areas and some alkyd-painted areas, wet latex paint can emit ammonia. To avoid the yellowing, if you must use both latex and alkyd, be sure the latex paint is dry for at least a day before applying the alkyd. The second source of ammonia is from household cleaning products. Avoid such cleaners if you have alkyd paint.

OTHER YELLOWING SOURCES: Yellowing may also be caused by cooking, by fireplaces or by smoking. All those sources can release microscopic particles into the air, which are attracted to your paint surfaces. If you have a yellow film from cooking, using the fireplace or smoking, it will need to be removed before a fresh coat of paint is applied. For double protection that no discoloration will bleed through your new paint, after cleaning, use a coat of KILZ primer before applying your new, fresh paint.

WHAT TO DO: Unfortunately, once the yellowing has occurred, it cannot be reversed. The only solution is to repaint the areas which are yellowed. Again, priming with KILZ will prevent any bleed-through.


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