Inside our homes we’re surrounded with wonderful finishes… by wood furniture, cabinets, millwork, as well as other wood things and without much thought we simply expect them to last an eternity.
The finished wood things we've got outside aren’t so fortunate. They’re exposed to the extremes of solar radiation from the sunshine… wetness in the types of dew, rain, and snow…. high temperatures… freezing cold… fungal strikes… and sometimes foot traffic. Good outdoor completes protect the wood from these conditions that are harsh, but will definitely fail unless they're renewed on a scheduled basis. Care is a necessity for outdoor wood finishes.
Choosing an Exterior Wood Finish There are a number of exterior wood finishes with distinct characteristics and properties. You will need to coincide with the product together with the project and make some decisions at the same time to choose the best one. These will be the crucial factors and concerns to find the finish that is very best;
⦁ Function – Which finish is the best option for the job you're focusing on? For example, the finish you are using in your deck isn't always the very best choice for your new solid mahogany entrance door.
⦁ Life Cycle/Care – some finishes continue longer than others, but none last forever. How often have you been ready to scrub, scrape, and/or sand and recoat the finish (i.e., weeks, months, or years) and how simple do you need the upkeep and repair procedure to be?
⦁ Appearance – should the finish be clear and bring out the beauty and depth of the wood, lightly colored and semi-transparent, opaque like paint, polished (shiny), matte (dull), or appear “natural” – virtually undetectable so that it’s not evident the wood has a finish?
⦁ Application – Given a choice, if the finish be relatively easy to apply or are you currently prepared for a product that requires more work and abilities that are advanced?
⦁ Price – How important is the cost?
Unfortunately, no finish scores well in most categories – you need to select a product that fits you as well as your job the very best. There’s take and give in the selection process – for example, the finishes that are most easy to employ and maintain don’t continue as long as others as well as the ones that continue longest are more expensive and more work. The one thing they all have in common is that they should be recoated every so often to keep up their protective qualities.
Is a Finish Really Necessary? In the event you like the look of silvery gray weathered wood, you may be considering leaving your job bare and avoiding the time and expense associated with keeping up and using a finish. If the wood is naturally resistant to decay along with the climate is just right, there’s a chance will develop the weathered appearance in time. There’s a better opportunity the wood will get dirty, grow mildew, and turn black and green.
Weathering and Decay In the outside, the forces of decay and weathering destroy bare wood. Weathering alone is a slow, deliberate process. Exposure to water and sun erodes the face of the wood. The grain raises, as it erodes and tests and cracks develop causing the top to become rough. The fractures grow and start to become larger as the boards cup, warp and twist – eroding or pulling away from fasteners. The roughened surface will change colour and accumulate dirt, particularly on the horizontal surfaces. That is a process that is slow and generates outcomes as shown in the photograph.
Fungus causes rot and breaks down the wood much quicker than weathering. Mildew is an airborne fungus that lives on organic stuff like dirt, pollen, and wood. In most of the U.S. the climate has the right mix of warmth and dampness that lets mildew to prosper. It host and will attract other fungi and develop rot in the event the wood remains damp. In climates which might be dry as well as primarily cold, decay is not as common or nonexistent.
Decay Resistant Wood Species Finished or bare, the very best wood for outdoor jobs is the heartwood from a species that naturally resists decay. Some woods that fit the description are accoya, catalpa, cedar (Spanish, western red, eastern white, or Alaskan yellow), chestnut, cypress (old growth is greatest), ipe, juniper, locust (black), mahogany (Honduras or African), mesquite, mulberry, oak (bur, white), redwood (old growth is greatest), sassafras, teak (old growth is greatest), walnut, yew, and pressure treated lumber.
United using a properly maintained outdoor wood finish, these species will appear great and last a long time outside. All outdoor wood finishes fall into two general types – penetrating finishes and picture forming finishes. Let’s explore properties and their features.
Penetrating Finishes Strengths ⦁ Don't blister and peel off
⦁ Usually do not have to be scraped or sanded – they wear away
⦁ Let out the wood dry and breathe
⦁ Simplest to employ and recoat
⦁ Natural looking
Weaknesses ⦁ Offer little protection from soil and wear
⦁ Want care more frequently than other products. Penetrating finishes usually double and last three months to your year on horizontal surfaces as long on vertical surfaces.
⦁ Don't bring the depth and beauty of the wood out
Seal it from water and penetrating finishes are made to soak to the wood surface. They usually do not offer any protection against wear and just somewhat protection from your sunlight, if any. However, penetrating finishes would be the simplest to implement and preserve and come in a choice of formulations that includes water repellents (WRs), water repellent preservatives (WRPs), coloured WRPs, teak oils and tung oils, and semi-transparent stains. Makers appear to be blurring the lines between these finishes which can make it challenging to determine just what is in the can. A broad guideline is the more natural appearing the finish, the less protection more frequently it'll have to be rekindled and it offers.
Water Repellents and Water Repellent Preservatives
Water repellents (WRs) (note – not waterproof) and water repellent preservatives (WRPs) leave the wood with an all-natural appearance (it might not be obvious the wood has a finish – particularly a couple of weeks after it’s applied). They have been clear/transparent and help reduce cracking by limiting water absorption and warping. The standard ingredients for WR finishes are a drying oil or varnish resin, and a solvent, paraffin wax. The solvent helps resin and the wax soak into the top layer of the wood before it evaporates. Adding a mildewcide or wood preservative to the mixture shields the wood and causes it to be a WRP. Some WRPs use a paraffin oil as the solvent which additionally serves as the preservative. The non-drying oil makes the face of the wood greasy for a time. Some of the newer WRPs on the marketplace incorporate a small quantity of pigment that adds a little colour and extra protection.
To help decrease the amount of volatile organic compounds (VOCs) released into the atmosphere, some of the newer finish formulas are based on waterborne technology. In the event the directions say to clean or thin up with water, it’s a waterborne finish. A drawback of waterborne finishes is they don’t soak to the wood together with the solvent based finishes which causes them to form a very thin film on the surface.
Some WRPs can be top coated with paint (check the label) and help to preserve the wood better in relation to the paint alone. It’s a good option on horizontal surfaces and the first few vertical feet (e.g., painted window frames, door frames, and doors).
Water repellent preservatives (WRPs) are the finish of choice for wood decks. They can be brushed on wet and given time to soak into the upper layer of the wood before the excess is wiped off. The end grain of the wood will soak up more as opposed to level grain which includes the advantage of protecting it longer.
Marine Varnish
Top quality marine varnishes are often used as the “gold standard” for exterior clear finishes. That’s because they have been exposed to wood degradation to a lot of water and sunlight, the two largest dangers. Traditional high quality marine varnishes are invented with UV inhibitors, tung oil, phenolic resins, and biocides. Neglect and varnishes centered on alkyd resins have a tendency to oxidize too fast when used outside.
More recently, uralkyds (also referred to as oil-modified urethanes) have become popular since they provide greater durability and water resistance and are less expensive. Nonetheless, conventional varnishes are easier to keep since they've better adhesion properties and don’t consistently need to be sanded between coats.
Exterior Paint
Paint offers the longest lasting protection – it blocks the UV fully and seals the wood from water and microbial attacks. It’s a good alternative on doors, trim, and wood siding along with outdoor furniture that doesn’t get wet too commonly. Siding and trimming should be caulked to prevent water from getting behind the paint and inducing it to blister and peel.
The ingredients of paint are the clear finish (called a binder), pigments, and additives. The binder functions as the glue that holds everything together and forms a thin film on the surface of the wood. The pigments give you the colour and make the movie opaque which blocks UV. And additives like biocides enhance the functionality and longevity of the paint. The film forming the rate of moisture transport slows into and out of the wood, but the wood is still vulnerable if it’s exposed to the conditions that encourage decay. It causes blistering and peeling when water gets trapped behind a picture forming finish.
The best option for outdoor wood paint is acrylic latex. Top quality acrylic lasts longer than oil-base paint as it has better resistance to UV. Acrylic latex can also be more porous than oil-base which lets the wood breathe and shed water. Lastly, acrylic latex is more flexible than oil-base paint and doesn’t become brittle and crack.
NOTE: When painting horizontal surfaces, or some vertical wood near a horizontal surface, it’s a great idea to apply a water repellent preservative (WRP) a couple of days before the paint (make sure it’s one that can be painted). This will definitely extend the service life of the wood by shielding it from the water that splashes on door jamb the ground, or window jamb causing rot.
Make sure you sand the wood before applying the primer to ensure you get great adhesion. Without sanding first wood that’s weathered for a day or more should not be painted. Follow the primer with two coats of paint in accordance with all the manufacturer’s directions. You’ll when the paint weathers away, understand it’s time to get a fresh coat and the primer begins to reveal. Don’t repaint too often overly avoid making it too thick.
Semi-Transparent Stains
Semitransparent stains have the similar ingredients as water repellent preservatives (WRPs) together with the inclusion of a large number of inorganic pigments (clay and soil up rocks) which alter the woods’ natural colour. The pigments usually are not changed by ultra-violet (UV) light and do a good job of blocking it from the wood. The less UV that gets through to the face of the wood, the less damage it can cause (that’s why paint does such a good job).
The pigments (and preservatives) are held in place by a thin resin (called a binder) which behaves like glue. As the binder breaks down over time (largely from UV damage), the pigments wear off and increasingly expose the wood surface. Ultra-violet (UV) light from the sunlight damages the wood by breaking down the lignin. Lignin functions as the glue that binds the wood fibers together and provides the wood its natural colour. Silver grey turns and erodes, as the lignin breaks down.
They allow visible light to pass through making them practically invisible when inorganic pigments are ground exceptionally fine. Nevertheless they can be large enough to block UV light which has a shorter wavelength. These pigments are either transparent iron oxides (transoxides) or titanium dioxide. The pigments help to guard the binder in the stain which prolongs the service life of the mildewcides and preservatives and keeps the pigments in place more.
Top products are relatively pricey though cost is just not a guarantee of functionality. Good quality ingredients – resins, pigments, and preservatives – are costly and necessary for maximum longevity.
Semi-transparent penetrating stains perform best on rough sawn or weathered wood like wood siding or on deck and fencing railings and posts. They are not an excellent option on the walking surface of decks where people walk since they show wear routes. If used on smooth fence planks, they ought to be power washed or wetted and allowed to dry a couple of times before staining to open up the pores.
If the wood is dirty or has mildew, clean it well before applying the stain (use a deck cleaner – not soap). In case the wood is weathered but clean, you can apply the stain without any preparation (unlike paint).
Follow the instructions on the can and put on the stain with a brush, spray, or roller. The directions may require if you utilize a roller or sprayer – that’s to make sure that the stain is worked into every one of the cracks and crevices that you back brush. Cool overcast days are best for applying stain so it's a chance to soak in before it dries.
Heat resistant coating for wood
Dirt road dust control
Protecting the Finish and Wood from UV Light
Via a process called photo-degradation, ultraviolet (UV) radiation damages the wood as well as the finish. At the surface of the wood UV breaks down the adhesive (called Lignin) that holds the wood fibers together. In the finish the UV breaks down the chemical bonds in the polymers that produce the clear finish and paint binder. The hints of this damage include reduction of polish, chalking, fading, cracking, and physical changes like brittleness and cracking. The top protection is provided by paints since the pigments that give them their colour also obstruct the UV from reaching the surface of the wood or beyond the face of the paint. For finishes that are clear, we want the finish or another solution will fail immediately, developing a major repair effort.
To counteract photo-degradation when it has to contain additives that efficiently block UV from reaching the wood or breaking down the bonds in the finish itself. In the 1970s, coatings formulators began using UV additive in finishes called ultraviolet light absorbers (UVAs) and hindered amine light stabilizers (HALS). These UV additives have greatly enhanced the durability and longevity of clear finishes used outside. Needless to say, chemists keep to enhance the performance of UVAs and HALs, and have. It’s potential for clear finishes to continue multiple years in exterior applications, now.
