Light and Ultra Violet radiation (UV) contains some energy that catalyzes chemical reaction leading to deterioration. The two main ways that one can measure the response of light is through Color Rendering Index (CRI) and Color Temperature (CT). CRI may be measured in a scale of zero-100. However, the museum lighting designers have suggested 80-100 so that colors can be viewed properly but does not also affect the painting. The level of light in museum is always measured using light meters in lux or using foot candles. This is the measurement of the intensity of the light over one square meter. Sometimes watercolor painting may be placed on exhibition for some months at a level of 50 to 150 lux and yet they do not show some fading. Lower light levels of 50-150 are important for light sensitive materials like watercolor painting. The extent of damage can always be measured lux hours (lx h) the maximum level of light exposure that watercolor painting can sustain annually is 50,000 lxh. Another very important aspect of protection of the watercolor painting is to ensure that the painting is kept off places that have fluctuation of humidity and temperature. The best temperature that would ensure that watercolor painting is stored safely is that which is around 20 degrees F. Places where temperatures may drop to 40 degrees and goes up to 80 degrees at night and day respectively, may not be the best place to store watercolor
Fluctuation in temperature usually has a very severe effect on the watercolor painting. When exposing the painting into light, it should be observed that the painting needs not be kept on light for prolonged period of time, especially with too bright light of all types. Watercolor painting always demand that they are kept in places that are not damp. Damp places usually enhance molding, which has ability to promote coloring change.
Sometimes the water color painting may be framed under glass.