Thermal stability of linseed oil paint

When you see a house with flaking paint (like the picture below) it means the plastic in the paint has cracked because of temperature fluctuations and expansion and contraction of the timber. 30% of acrylic paint is composed of plastic polymers and when the paint goes onto a surface those plastic polymers harden leaving a plastic skin that covers the surface.

The problems occur when there are rapid temperature fluctuations and the plastic in the paint softens in the heat then in cold temperatures (like when there is a frost) the plastic skin becomes brittle and cracks. These cracks then allows moisture to get under the paint and because the plastic paint is not breathable it traps the moisture between the plastic and the surface. This trapped moisture then causes deterioration of the surface, whether it be wood, plaster or metal.

When using linseed oil paint the situation is totally different. Linseed oil paint it is a far more thermally stable paint, there is no plastic surface and the linseed oil paint is permeable, so no moisture is trapped to allow the wood to rot and fungi to get in there and really cause damage.

Another advantage of linseed oil paint being thermally stable is that it stops the wood it's painted on from warping on hot days. Some people like to paint there timber homes and fences in black, but on hot days the black plastic paint really heats up, to such an extent that it causes the wooden boards it is painted on to warp. This problem doesn't occur if linseed oil paint is used.

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