White paint going cream

[rota]

Hi,

Just wondering if anyone has had this problem or may know of this problem...I had my house painted 8 months ago and noticed that the arch's and doors are going from white to cream. Its oil base paint Wattyl id. I was advised that this would happen where the paint does not see much light, (which in fact is right its worse in areas where its darker) but it amazes me that this issue with white paint. Any thoughts would be great.

Thanks

[mic-d]

Hi Rota, welcome to the forums. Do a search for this, it's been done before.

Cheers
Michael

[rod@plasterbrok]

Yes it has happened at my place under vases in the powder room etc.

[Sturdee]

Hi,

.... noticed that the arch's and doors are going from white to cream. Its oil base paint Wattyl id.

That's your problem. Oil based white paint will change to cream. The speed of change depends on how much sunlight it gets.

BTW its not the brand, as all oil based white paint do it, so use acrylics instead for that doesn't have that problem.


Peter.

[ADDS]

Put some black tint in the paint next time. what it does is it slows the process to cream down, as it takes the edge off the white. B1 for a four, B2.5 for 10 and B5 for twenty

[Ian Wells]

Although I cant say exactly what the Wattyl ID has in it as its binder , I'd say its probably a Linseed or Soy oil modified Alkyd resin . These like all oil based paints dry by the oil part absorbing oxygen and polymerizing. The Truth is that like the other in this post have said, they all yellow, its just that the better paints have more pigment in them so that the yellowing of the binders are less noticeable.Also the metallic driers the manufacturers add exacerbate the problem by increasing the oxidization (absorbing oxygen) The only sure fire way I know to reverse the yellowing is to get sunlight or some other source of UV light on to it. Stay away from chemical bleaches as they'll weaken the paint film.
Also the ammonia in many acrylic paints can darken the alkyd resin part of many oil paints ....not sure why will ask the guys at the factory and post later
I hope this at least answers the why? part of your question.

ps. it wouldn't be sulphides darkening it, as that only happens with lead based paints.
pps. Acrylics darken as the surfactant in them comes to the surface and traps dust . they also darken because they are water permeable and draw in atmospheric pollutants or draw up tannins etc from the underlying timber.

regards

Ian

[la Huerta]

painted the skirting boards here many times because the damm white paint went cream...and yes it was oil based...

[dan76n]

http://www.apmf.asn.au/html/fact_sheet_pages_1.html