Stain protection is accomplished mainly by three methods; pigment, vehicle and bio protection. These three methods are the materials left on and in the wood and endure ongoing exposure to the elements, water, temperature fluctuation and ultraviolet light. To effectively protect and preserve the wood from all the elements, there has to be a comprehensive formula that works in a synergistic manner to refract ultra violet light, repel water while allowing the wood to expand and contract and fight micro organism attack (mildew/fungus).
It is a proven fact that Semi-Transparent stains do hold up better than Transparent stains in harsh hot climate areas due to their ability to better block U.V. sun light. The Semi-Transparent stains have a high pigment loading as opposed to the Transparent stains, providing a “hiding” effect, hence the term Semi-Transparent. Transparent stains use expensive Trans-Oxide pigments which have been known to block U.V. light as well and allow for the “transparent” look, but have limitations due to the lower pigment loading and must be selective for intended end use.
For example, when staining an older (aged) fence that has been weathered the Semi-Transparent stain functions and looks better in appearance than the Transparent stain, by hiding all the discolorations and imperfections in the wood, yielding a more uniform look. On the other hand when staining a new clear cedar fence (selective) the transparent will show the natural grain of the wood along with protecting the cedar from darkening or discoloring.
In conclusion, both stains have their place and serve a purpose. The Semi-Transparent stain is more widely used because of its “heavy duty” formula, offering a universal product for multiple uses, new and aged wood alike. Transparent stains work well in selective areas offering a natural look allowing for the natural wood grain to be highlighted; knowingly more re-applications will be required in harsh climates versus the Semi-Transparent stain.