based on physical, chemical, and biological ages of deterioration. The top layer of substrate is more susceptible to biological and physical weather damage such as weather conditions while lower layers are susceptible to chemical damage based on the microbial deterioration. In order for conservators to create a plan to protect and analyze historic paint, they must understand how the agents of deterioration affect the historic paint. Light Light is a common threat to historic paint analysis. Light deterioration agents cause oxidization and other degradation of the inorganic and organic pigment components, as visible light "fades (bleaches) or darkens the outer layer of paints." For historical murals and buildings, air pollution causes disintegration, discoloration, or corrode the paint murals and facades. Chemical interaction There are many factors that can lead to degradation resulting of chemical interaction. One of these results of the medium of suspension such as occurs when pigments are dispersed in the medium of linseed oil, which will cause yellowing over an extended period of time. To offset this reaction and prepare samples for analysis, "target areas are exposed mechanically and prepared for color matching. Samples are then light bleached for two weeks under a fluorescent tube to reverse darkening and yellowing of linseed oil. Samples are then measured with a chromameter. The conservator should have knowledge of historic architecture and building history, architectural finishes and their materials and manufacture, and an understanding of how color and pigments age." Biodegradation Many elements in the natural environment can lead to the degradation of paint - biological activity not being the least amongst them. Microorganisms, fungi and algae can degrade the pigments, binders and medium of suspension and substrate through their respiratory activities. In his article, Microbial Degradation of Paintings, Orio Ceferri sites the following: “...cyanobacteria and algae growing on paintings ex- posed to light, such as frescoes on the facades of buildings, may cause considerable damage. Besides the aesthetic damage caused by a green, black, brown, or yellow algal patina covering the painted portions, these organisms may cause weathering of the surface layers, accelerating detachment of portions of the painted layer as well as the underlying plaster”. Incorrect temperature Incorrect temperature causes paint layers to crack and causes fractures in optical microscopic samples. At lower temperatures, "materials such as varnishes, lacquers, wood, oil, alkyd, and acrylic paints are especially at risk and need to be handled with extreme care". Similarly,