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Sand animation or sand art is the technique and the act of painting via a non-traditional medium, which is sand. A video of a sand painter may show the layering and blending technique they use from beginning to end to create complex sand paintings, or it may show a looser style in which they draw in sand as a medium rather like finger-painting, constantly changing the image and wiping out their canvas only to start again. Part of the appeal of sand painting is the impermanence of the media and as such, it may be perceived as a type of performance art.
For more information on the subject of sand animation, click on the link which will take you to an article at About.com: http://animation.about.com/od/faqs/f/What-Is-Sand-Animation.htm