Elegant in both technique and character, watercolors and gouaches are essentially created from the subtle combined effects of paint and liquid, usually rendered on a textured paper surface (the ground). Watercolors, made from finely ground pigments combined with a water-soluble binder such as gum arabic, allow a unique blending ability not found in other media, and can achieve varying degrees of transparency after drying. Gouache, or opaque watercolor, on the other hand, is a denser paint that fully covers the underlying surface in one coat and characteristically renders a flat matte surface. Because of the translucence nature of the paint combined with the fragility of paper, both types are particularly susceptible to environmental and handling hazards—ensuring that they retain their beauty and color through time may require special care.

The first step to assuring the longevity of a watercolor or gouache is ascertaining the quality of the materials from which it was created. If possible, find out if the artist used non-acidic paper for the ground; if not, even the most careful handling will do little to overcome the inherent problems that exist with cheap acidic paper made from wood pulp. The best papers are made from 100% rag fiber (cotton and linen) and can last for centuries if treated properly. High-end paints (with a light fasting rating of 1 or 2) should also be used; inexpensive ones can become light-struck, a term that refers to the fading of some pigments, and a complete loss of others.

If not already framed, the artwork should be as soon as possible to protect it from dirt, dust, and handling. Until that time, it should be placed between two pieces of acid-free paper, laid flat, in a cool, dry, dark place. As with the ground material, 100% rag fiber matting in either 4- or 8- ply thickness should used because acidic matte material can cause burns in the painting where it comes in contact or can attract destructive parasites. Both the front and back mattes should be hinged at the top with white linen tape or Japanese rice paper and rice or wheat starch paste. Transparent tape, which can stain and burn the matte over time, should never be used to hold the painting in place.

Glazing is another critical aspect of the framing process. Rather than using non-glare glass (although finely etched to reduce reflected light, it actually absorbs light), use materials such as UV3-coated Plexiglas or Denglas to protect the paints and paper from fading. But never use glass cleaners that contain ammonia on Plexiglas or any acrylic glazing as it will yellow the surface; use a very mild detergent solution and a soft cotton cloth, or a special cleaner made especially for Plexiglas instead. Never place the painting directly against the glazing surface as this may trap in moisture, causing damage; the back of the frame should be sealed as well to keep out dust and insects.

For any artwork that has a high monetary or sentimental value, it is worth the investment to have it mounted, matted, and framed by a licensed, professional framer.

The environmental factors of light, dust, heat, and humidity are also enemies of fragile watercolor and gouache paintings. The artwork should never be hung where it will receive any direct sunlight. Over even a small amount of time, the ultraviolet light in sunlight can begin to fade the pigments and dry out the paper. It is advisable to hang a watercolor in a room with diffused incandescent or halogen light. Fluorescent lighting is as damaging as sunlight, producing ultraviolet light in high concentrations. If lighting is applied directly to the painting, be sure the light fixture is at least 8 -10 feet away.

The best environment for art created in this media is filtered air below 70 degrees at a relative humidity between 50-65 %. Usually home HVAC system is adequate, unless the area has high levels of pollution or dust. Heat and humidity fluctuations play havoc with organic materials such as paper, so even if it is not possible to keep art at the optimal conditions, it is more important that it is not subjected to dramatic changes. Thus, avoid placing a watercolor over a heating vent, or over the fireplace, or by the front door. Even an outside wall could be problematic if not properly insulated.

Art conservators have techniques they can employ to restore some aspects of damaged watercolors or gouaches such as removing foxing (the development of patterns of brown or yellow mold stains on the paper), repairing tears, and grime removal. Unfortunately, very little can be done to return the pigments back to their brilliant, original state once they have begun to fade. The key to their longevity rests in proper preventative care before the damage can occur.