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Abdi,
It is important to understand that an oil paint film loses its flexibility as it gets older, and ultimately becomes brittle. So if the support on which it is applied is not stable, the paint layer will crack when the support changes its shape due to the pull of gravity, handling, temperature changes, or when there is movement in the air for any reason. This is what happens to old oil paintings on stretched canvas. When the paint cracks, the integrity of the surface is interrupted, and the lower layers are then exposed to the atmosphere, dirt, and whatever might be applied to the surface in cleaning the picture. This can weaken the bond between the paint and the ground if they are chemically dissimilar, as acrylic grounds and oil paints are. Oil and alkyd grounds achieve a chemical as well as physical bond with oil paint, whereas the bond between acrylic grounds and oil paints is physical only. Thus it is reasonable to assume that the bond will be better with an oil or alkyd ground, and the likelihood of paint becoming detached from the ground would be less than it would if the ground were acrylic. However, the biggest problem is the lack of rigidity in the support. This can be taken care of by gluing the canvas to a panel, as museums
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