Contemporary paintings executed in the Color Field technique require special care. The Color Field movement, which began in the 1950s, broke the long-established rule that canvas must be sealed or primed. The movement was made possible by the development, around 1950, of acrylic resin paints, which do not yellow or chemically attack raw canvas as do oils. The paintings produced by direct application techniques are like gigantic watercolors structurally, yet most people who handle them operate under the assumption that they are as physically robust as conventional paintings. Some simple measures, primarily guidelines for handling, can greatly slow the natural aging process of Color Field paintings and minimize the human damage to them. Soiling is a major problem, and the difficulty of cleaning and retouching makes prevention a priority for these paintings. Paintings should be handled as little as possible, and should be stored and transported in a frame. Writing and affixing labels to the backs of the canvas should be avoided. Backing the painting with a light, rigid material is recommended. Place a plastic wrap over the painting, but avoid contact with the surface. Folding or unstretching, of course, should be avoided.