Clear stains or coatings are often used when customers would like to retain the original appearance of the wood surface. Clears can look beautiful as it often gives the appearance of a "wet-look" and provides the graining with greater contrast. The protection provided a clear application is often the shortest life-span out of any of the coatings. The lack of color pigment within the coating itself allows sun and other weather to penetrate it often between 1-2 years.
These stains are one-level more opaque than the clears previously described. Grains can be seen easily through the stain while adding some color flavor to the surface. In regards to the durability and longevity of semi-transparents, they often last between 2-4 years before a re-application is required.
Moving up the opaque-scale, semi-solid stains have a density to them which allow for roughly 40-50% of the wood grain to show-through the coating. If you have heavy knots and heavy graining within the wood, this is a great option to use because you have a much longer life-expectancy than the transparents... yet you will still see some of the heavy graining. These coatings typically last between 4-7 years between coatings.
Just like a paint, a full-solid stain is 100% opaque in nature and does not allow any wood grain to show-through. For those who are interested in having the most durable, longest lasting stain available, this is it. Typical life-spans for a solid stain range between 7-10 years. The main difference between a solid stain and paint is that the stain penetrates into the wood while the majority of primers and paints stay on the surface. You will not get as much "flaking" with the solid stain as you would with a paint after 10 years. Full solid stains can be tinted to any color out there.