Exterior stains, or more specifically Exterior Wood Stains, are used to change the natural color of wood. There are four main categories of exterior stains:

  • Translucent
  • Semi-Transparent
  • Semi-Solid
  • Solid

Following is an example of each:

Raw pressure-treated pine (no stain)
Pressure-treated pine with translucent stain (Sikkens SRD “Natural Oak”)
Pressure-treated pine with semi-transparent stain (Benjamin Moore ArborCoat “Natural Cedartone”)
Pressure-treated pine with semi-solid stain (Benjamin Moore ArborCoat "Natural Cedartone")
Pressure-treated pine with semi-solid stain (Benjamin Moore ArborCoat “Natural Cedartone”)

As can be seen, wood is most visible when using a translucent stain and becomes less so as you move from semi-transparent to solid stains.

It is important to note a few things about exterior stains:

  1. Color matters. The type of pigments (referred to as “colorants”) used to achieve a given stain color is VERY important. Not all colorants are created equal. Some hold up to the sun’s UV rays far better than others. That is why most manufacturers have more limited color selections for stains versus exterior house paints. You may be asking, “Why can exterior paints use colorants that should not be used in stains?” That is a more complex answer that has to do with actual coating chemistry and will be addressed in a future article.
  1. Don’t assume your interior stain can be used outside. This is by far the most common mistake made with wood stain. Typically, a customer will come to us looking for the best exterior clear finish they can find. Then they inform us, “I have already stained my door with (insert product name here).” In this case it is a product intended for interior use. We unfortunately must inform them that even the best exterior clear finish cannot protect the interior stain from fading underneath the exterior clear finish. The clear finish itself will hold up well (though not as well as if the proper system had been used), but the stain will slowly fade out. So, if the customer intends to proceed with the proper exterior product system, they must strip the surface and start over in a few months once the stain begins fading.
  1. The relative performance of exterior stains are as follows: Solid Stain > Semi-Solid Stain > Semi-Transparent Stain > Translucent (with solid stains requiring less frequent maintenance intervals than translucent stains). This of course assumes you are choosing from the same caliber brand of stain. So be aware that you may be giving up longer term performance to achieve a particular aesthetic.
  1. Not all exterior surfaces are created equal. Just because a stain is exterior-rated does not mean it can be used in all exterior applications. The least demanding exterior applications are vertical surfaces (fences, siding, etc.), while the most demanding are horizontal surfaces (decking, porches, handrail surfaces, etc.). Keep in mind the two biggest enemies of an exterior finish are the sun (UV rays) and moisture. The more exposure a finish gets to one or both of these, the shorter the life of the finish will be.

That said, let’s go over the four exterior stain types.

Translucent stains are most similar to the aesthetic provided by interior wiping stains. They offer the richest and deepest color options of the four stain types, and they offer the highest visibility of the underlying wood (i.e. they don’t “cover up” the wood as much as the other stain types do). True translucent stains, such as Sikkens’ Cetol line of exterior stains, use highly specialized colorants that provide the deepest and richest looks available and that simply cannot be achieved by the other stain types. Keep in mind future maintenance coats will continue to darken the surface and slowly “cover up” the wood as you are adding more color with each maintenance coat.

Semi-transparent stains offer a much wider color pallet than translucent stains. They cover the wood a bit more than translucent stains, but the wood can still be seen. Like translucent stains, keep in mind that each time you apply a refresher/maintenance coat, you will further cover the wood as you are adding more color each time a coat is applied. That said, Benjamin Moore offers a clear maintenance coat that can be used in order to prevent this from occurring.

Semi-solid stains are just like semi-transparent stains only they have more body/color thus offering better protection, but covering the wood more than a semi-transparent stain. Like translucent and semi-transparent stains, each time you add a refresher/maintenance coat you will further cover the wood. With a semi-solid it is likely the wood will be covered after adding a single maintenance coat of semi-solid stain. To help avoid this from occurring, Benjamin Moore has developed a clear maintenance coat, as mentioned above.

Solid stains, as the name implies, completely cover the wood surface just as if you were using a traditional paint. The key difference between a solid stain and a paint is that the solid stain is thinner than paint (think of the consistency of shampoo versus molasses for example). As a result, the solid stain penetrates into the wood surface better than a paint. And though you can’t see the surface of the wood itself, you will still see the grain and texture of the wood. The other benefit of a solid stain being thinner is that if small amounts of moisture happen to get into the wood, the solid stain can “breath” better than a paint, thus allowing the moisture to slowly escape and not get trapped under the stain. This enhanced “breath-ability” helps reduce the chance of the solid stain peeling away from the wood.

We hope this article was helpful for you. Stay tuned for future topics, and please contact us if we can be of help on your next project! Also, please let us know if there are specific topics you would like us to cover in the future – we would love your feedback. Thanks for reading!

Note: always thoroughly read the manufacturer’s product label, technical data sheet (TDS) and Material Safety Data Sheet (MSDS or SDS) prior to using the product. The manufacturer’s information always takes precedent over any information provided by Hunter Coatings.

by Andy Stanush