Lime wash is basically lime putty that has been watered down and can be easily applied to various surfaces. The slaked putty can be administered with its natural hue, or just about any color can be added before it is applied. Because it typically contains small calcite crystals, the finish of the wash will often seem to provide a slight glow in the open light.
People use lime wash in the same manner as any type of white wash. Its purpose is not to add a total covering to a structure, but to include a thin layer of protection that will help to enhance the underlying appearance. Like white washing, the lime is not a permanent cover, and constant exposure to the elements will eventually wear it away, and a new coat will need to be applied.
As an example, a wooden wall that is painted red and treated with a pure lime wash will still appear to be red, just a muted color. The wash can be adjusted to allow more or less of the underlying color to show through by adjusting the amount of liquid in the solution. Some people prefer the added texture that a light washing will add to a painted surface, while others prefer to go with the thicker application and the enhanced protection.
The art of the lime wash has been around for thousands of years and practiced in several cultures. It's important to note that this wash not a painting technique, although it may be applied with paintbrushes, but is, in fact, more of a staining technique. The properties of the lime seep into the pores of the wood or masonry and effectively become part of the material. Over time, the natural aging process will give the surface a certain glossy patina that is considered by many people to be very attractive. Even when most of the lime has faded way, traces will remain that help to enhance the look and character of the surface.