Does Stain Protect Your Wood From Moisture?

When you’ve chosen the wood carefully for your project, chosen it for its natural beauty and the grain that will present when it’s seen, you want to preserve that beauty and allow the grain to show through.  Paint will hide that beauty and cover the grain, so we turn to another option.  

Among the options are stain and wood oils.  Wood stains come in a variety of colors, light to dark, but do allow the natural beauty of the wood, as well as the grain you chose it for, to be the star of your project.  Wood oils will do the same thing, but today we’re considering wood stains.

What Is Wood Stain?

Wood stain is a type of paint that will add color to your wood surface.  In stain, a colorant is dissolved in a solvent, and when applied to wood surfaces, will soak into the wood fibers and will bind to the wood when it has dried.  It is distinguished from paint in that it saturates the color into the wood rather than forming a layer of color on the surface of the wood.  

Stains will add some protection to the wood, most importantly against the harmful effects of UV rays.  UV rays will damage wood fibers, weakening them to the point where wood can warp, crack, or warp, thus damaging furniture, fencing, decks, and other wood structures.  Of course, this happens only when wood is exposed to direct sunlight.  For indoor furniture, this is not a concern, of course.

Even though stains will soak into wood, though, and will frustrate other materials from also soaking in, that is not the same thing as saying stains will protect your wood from water or other moisture.  While it may offer some resistance to moisture, further measures will be needed to provide full protection.  

It is worth noting that some stains do contain ingredients that can offer an environment hostile to insect infestation, as well as mold and mildew.  In fact, water-based stains are particularly effective in preventing mold from forming.  If a stain also includes zinc nano-particles, it will have a greater ability to ward off mildew.

Water-Based Stains

General Finishes Water Based Wood Stain, 1 Quart, Espresso

Water-based stains are a good choice for finishing your project.  They will tend to last longer than oil-based stains as they have a greater UV resistance and are thus able to hold their color longer.  Water-based stains will penetrate deeper into wood than oil-based stains, also.  

Water-based stains are also a better choice for woods that already have a natural resistance to rotting.  Woods that fall into this category include cedar, cypress, and redwood.  

Water-based stains also pollute less than oil-based stains and are more eco-friendly.  They are also easier to clean up after simply with water and especially easier to clean up after than oil and varnish.  

Water-based stains will last 1 year if the container is opened and 2 years if unopened.  Oil-based stains, on the other hand, will last 1 year whether opened or not.

Oil-Based Stains

General Finishes Oil Based Penetrating Wood Stain, 1 Quart, Warm Cherry

Oil-based stains also penetrate into the wood and colorize wood fibers.  They will hold their form well over time, fading rather than peeling.  This does separate them from water-based stains, as water-based stains will peel over time, especially if you have applied too much and not wiped excess stain from the wood surface.  If it does not penetrate but dries on the wood surface, it is most apt to peel.

Oil-based stains are composed of petroleum distillates, varnish, and linseed oil.  Oil-based stains are flammable and have a distinct and overpowering odor that requires their use to be in a well-ventilated area, if not outdoors.  

Oil-based stains take longer to dry than water-based stains.  The longer drying time, though, has a slight advantage in that it allows for a more even finish.  However, that same even finish can be achieved with water-based stains if they are applied correctly.  

Many brand names have discontinued oil-based stains in favor of water-based, although their use is still permitted in the US.  The quicker drying time and easier cleanup make water-based stains a more popular choice today.

Is Either Water-Based Stain or Oil-Based Stain Waterproof?

Water-based stains are not very waterproof.  You should not count on them to protect against rain and water.  Water-based stains need to be sealed with a varnish, wax, oil, or even a film coating such as polyurethane.

Oil-based stains will offer a greater degree of protection against the elements.  If your project is going to be in direct sunlight and fully exposed to weather – wind, rain, and the sun’s UV rays – an oil-based stain is the better choice.  It is more durable than a water-based stain and can offer more complete protection for your wood.  

It is worth noting, too, that as much as oil-based stains can offer a greater degree of protection, they will not last nearly as long as a water-based stains.  

There is an old sailor’s expression – Keep a weather eye on the horizon.  When it comes to applying an oil-based stain on an outside project or simply used outside because of the ventilation, this is also an apt concern.  

If rain is in the forecast within 48 hours of applying a coat of oil-based stain, hold off.  The rain will be absorbed by the wood, and the moisture will attempt to displace the stain before it has had a chance to dry fully.  The result will be a spotted and blotchy finish.  If the rain falls immediately after an oil-stain application, the stain will simply peel and flake off.

Be sure, also, that the wood you are about to stain is fully dry.  Oil-based stains will tend to seal the wood, thus trapping moisture inside.  This will lead to rot eventually, and your project will need to be repeated.  

Stain-Sealant Combinations

For your outdoor projects where protection against rain and water is a concern, there are stain-sealant combinations available commercially.  

One of them is called Ready Seal Wood Stain and Sealer.  It contains everything you would need for an effective colorization and sealing finish.  It’s easy to apply and provides a quality finished project.

Should Stained Wood Be Sealed?

You’ve already read the differences between water-based and oil-based stains and the degree of protection each offers against moisture.  While oil-based stains can offer a greater degree of protection for your project, it is still wise to seal stains in general.

Those finishes include shellac and polyurethane, although there are other sealants that are just as effective.  Marine sealants like Thompson’s are an excellent choice, too.

You might wonder if a water-based polyurethane could be used over an oil-based stain, but the answer is yes.  Stains penetrate the wood and colorize the wood fiber; polyurethane is merely a film of plastic that does not penetrate the wood.  They will not compete with each other, and polyurethane is a water-proof sealant.

One product we have written about extensively on these pages is Rubio Monocoat.  You will find one article on point here, where we discussed this very subject.  While Rubio Monocoat is highly water-resistant, it is not waterproof; but Rubio also offers a topcoat that can elevate that protection against moisture.

Our video for this article is also directly on point – a comparison of oil-based (Minwax) and water-based (Behr) stains on pine.  

While each type of stain has its value in your woodworking shop, we tend more toward water-based stains.  Ease of use, quicker drying time, much easier to clean up after, no odor to offend, not requiring good air circulation, and with a top coat to fully waterproof the wood, it is a more appealing choice for us. 

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