An exterior wood stain is an ideal product to maintain and protect furniture and other wooden items which are exposed to the elements. Wood stains typically contain anti-fungal chemicals to prevent mold and algae from growing on your exterior woods, and water-proofing elements which will help protect against wood rot and diseases. Other wood stains contain preservatives, and non-penetrating stains.
These protect the wood against water penetration. Water damage can lead to rot and mildew, but water-proofing stains helps to seal the wood against damage. Some stains contain as little as 1% of waterproofing, as they are mixed with other agents, while others have around 3%, and are generally used as a finish.
Stains which contain a pigment are traditionally classed as penetrating stains. These kinds of wood staining products are resistant to blistering, cracking or peeling. These pigment stains often allow the wood grain to show beneath the finish, so they preserve much of the natural appearance of wooden furniture.
A more modern invention, these stains often contain latex or oil-based solid-color staining. These stains do not penetrate the wood, and should be applied to the wood like a pain or finish. Latex can be applied thinly so that it forms a semi-transparent stain, but they are often not thick enough to be durable on outside woods.