How to Seal Painted Wood for Outdoor Use
Outdoor painted wood furniture and decorative items such as the wood flower pots, doors, tables, chairs, although painted with finishes, are always constantly subjected to harsh daily weather conditions, including the scorching sun and heavy rain, all through the year. This is because the finishes are often subjected to wear and tear too.
Water can attack the wood with the growth of fungal, leading to wood rot. Also, continuous timber exposure to sunlight can weaken the wood. Protecting these woods against extreme weather conditions with wood sealants is therefore essential if they will last long. Hence the need to know how to seal painted wood for outdoor use.
Many products help preserve the integrity of outdoor wood. These products, commonly called sealants, help protect the woods against weather conditions, make cleaning easier, and keep the finish paint from peeling while maintaining their natural colors.
In this article, you will learn more on frequently asked questions about sealing painted outdoor woods like how to waterproof outdoor paints, the types of sealant best for painted wood for outdoor use, how to protect outdoor wood furniture from rain, the best exterior clear coat for painted woods and how to seal painted wood for outdoor use.
Can you put a wood sealer over painted wood?
Yes, wood sealant can be put over painted wood for outdoor use to protect the wood against external elements to last longer.
What is the best exterior clear coat for painted wood?
The best exterior clear coat is spar varnish. Spar varnish clear coat is best for painted outdoor woods because it is flexible. Hence it can move with wood with changes in changes in humidity. Spar varnish contains UV blockers which offer protection against scorching sunlight more than oil.
All at a Glance
How do you waterproof outdoor woods?
There are three ways you can waterproof outdoor paints:
Use of Exterior Oils: Linseed or Tung oil to create warm, hand-rubbed (wiping) oil
Over time, linseed and Tung oils have been used as a waterproof sealant mainly for dark-colored woods such as mahogany and walnut. To prepare a standard hand-rubbed oil, mix one-part oil (either Tung or Linseed oil) with one-part polyurethane and one-part mineral spirits and stir well.
Materials Needed: A garden sprayer or natural bristle brush, a clean rag
Application:
- Apply oil mixture with a natural bristle brush to dry surfaces and allow it to soak into the wood fibers
- Wipe off excess oil with a clean rag and allow the wood to dry overnight
- Sand lightly using fine-grit sandpaper
- Recoat again as many times as you desire.
- Re-application can be done once a year.
Exterior Varnish or Urethane (Sealing of wood with Polyurethane, Varnish, or Lacquer)
Polyurethane, varnish, and Lacquer, all referred to as “Vanishes,” have excellent waterproofing properties. They are all formulated to absorb UV radiation and moisture, preventing damage. Exterior Vanishes are flexible and are less likely to crack with changes in season.
However, while varnish resists scratches without discoloration, Lacquer, on the other hand, can develop a yellow discoloration over time.
Application:
- Apply up to eight thin coats with sanding in between
- Reapplication can be done after two to three years
Epoxy and exterior varnish combo
However expensive, this is the most durable finish for outdoor woods. Boatbuilders mostly use it as it is known to last long.
The epoxy creates an impenetrable barrier against moisture hence preventing swelling and shrinkage with seasonal changes. The exterior varnish, on the other hand, provides UV protection.
Application:
- Apply three to four thin coats of epoxy using foam coats
- Leave to dry before sanding with 100-120 grit sandpaper
- Wipe sanded epoxy with clean water and dry using paper towels
- Apply light coats of exterior varnish with light sanding in between
- Leave to dry overnight.
Types of Wood Sealant for Outdoors
To seal painted wood for outdoor use, you should choose the appropriate wood sealant or coating. Some wood sealants are suitable for painted wood, while others are appropriate for bare wood. Woods sealants suitable or compatible with painted wood for outdoor use are:
- Polyurethane
- Polycrylic
- Paint and sealer combination
Polyurethane: Polyurethane is a clear topcoat used for sealing exterior paints. Polyurethane, when used, helps to extend the duration of a finish. Polyurethane forms a shining protective covering on furniture, kitchen cabinets, and other outdoor woods.
Polyurethane exists in two forms: water-based polyurethane and oil-based polyurethane. Water-based polyurethane is most suitable for latex and acrylic painted finishes. Oil-based polyurethane can be used on painted and bare wood surfaces. It contains toxic volatile organic compounds; hence You should apply it in a well-ventilated environment.
Polycrylic: Polycrylic wood sealant is a water-based topcoat sealant that also helps protects outdoor woods from moisture and adverse weather conditions. Because Polycrylic is water-based, it is best compatible with water-based or flat latex paints only. Polycrylic wood sealant will not bind with oil-based paint or gloss.
Paint-Sealer Mixture: These products are a combination of paint and sealant in a can. No additional topcoat is needed with it. The paint-sealer mixture is mainly used to paint and seal white furniture, and unlike most sealants like polyurethane and Polycrylic, they do not cause discoloration on white paints.
Step by Step Guide on How to Seal Painted Wood for Outdoor Use
How do you waterproof outdoor paints? How do you seal painted wood furniture for outdoor purposes? How do you protect outdoor wood furniture from rain? And how do you seal your painted wood crafts? This step-by-step guide will answer all your questions on how to protect your outdoor wood of any kind.
Step 1: Identify the appropriate wood sealant
You should first identify the finish on the wood as either water-based or oil-based. You should use Water-based wood sealant on water-based or flat latex and acrylic painted finishes, while an oil-based wood sealant is best appropriate for gloss.
Step 2: Clean work surface before application
A clean surface is necessary for the clear topcoat to bond with the paint. Dirt, the oil may prevent the Polycrylic or polyurethane from sealing properly with the painted wood. Start by removing rough spots by sanding with 220-grit sandpaper lightly—clean dust and oil with a tack cloth to ensure a clean work surface.
Step 3: Stir wood sealant
If you must stir the sealant, stir gently to prevent bubbles from forming in
the fluid.
Step 4: Applying sealant on the wood surface
Here, you should note two important things: your brush and the way you paint.
Choosing the right brush for clear coat/ wood sealant
Choosing the right brush for painting wood that needs to be sealed is as vital as choosing the best clear coat over wood paint because the better the brush, the better your finishing turns out to be.
There are two types of brush: the natural bristle brush and the synthetic bristle brush.
Natural bristle brush swells when in contact with water, and they lose their shape. This can affect the appearance of your painted wood when you seal painted wood with Polycrylic wood sealant. Instead, use synthetic bristle brushes such as the Minwax Polycrylic Brush for Polycrylic sealant (water-based) and water-based polyurethane as synthetic bristle brushes do not swell when in contact with water. Use a natural brush instead for oil-based polyurethane.
Best way to apply Polycrylic and polyurethane wood sealant on painted wood for outdoor purpose without bubbles
With a quality painting brush, apply Polycrylic or polyurethane wood sealant on the wood surface. The best way to apply Polycrylic or polyurethane without bubbles is to dip the brush into a wood sealant can and do not wipe excess sealant on the can edge to prevent bubbles in the finish.
Also, painting in one direction and the direction of the wood grain prevents bubbles from forming. This also allows your paint looks as natural as possible when dry.
In addition, do not over-brush. Over-brushing makes your brush sticky instead of moving freely over the painted wood and can cause air bubbles to form as the painting dries. Keep painting forward rather than backward.
Smoothen out bubbles or drips when the coat is still wet and allow the sealant to dry for one to three hours, depending on the manufacturer’s instruction
Step 5: Sand lightly using 220-320 grit sandpaper. Wipe sawdust with a tack cloth.
Step 6: Apply wood sealant again for the first time and allow it to dry again to ensure maximum protection and durability of the wood.
Step 7: Sand lightly again and apply the sealant as before.
You can use three additional coats of Polycrylic or polyurethane wood sealants. Moreover, when you apply too many coatings or apply your coat too thick, it becomes sticky. Also, sanding between coatings and drying prevents your painting from having a sticky finishing. However, do not sand after the final coating.
Step 8: Dry wood overnight before using.
How to Seal And Treat Painted Wood For Outdoor Use
The best finish on outdoor woods wears out with time. It is essential to know how to seal and maintain outdoor furniture. Choose Finish with UV and moisture blockers: Choosing the best paint with UV blockers, an exterior primer top coated with oil-based paint, or exterior latex like Spar Varnish.
Sanding:
- Ensure you sand the wood to the bare wood to promote adherence to the wood
- Seal wood completely
- Recoat yearly or every two years
- Deliberate protect furniture from sun and rain. Putting outdoor furniture under shade instead of leaving them out in the yard will make them last much longer.
Wood sealants, though they help protect painted outdoor furniture, are not the best way to maintain the integrity of your painted outdoor furniture. Painting your outdoor woods with acrylic enamel makes it durable. Acrylic enamel is a waterproof paint, and it does not require any topcoat sealer against moisture.
In the same way, paints with UV blockers are better than a clear finish. They can last up to seven to eight years and are durable. Paints are capable of protecting outdoor wood from ultraviolet light and moisture. Exterior varnish is, however, the best.
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