A wood sealer keeps moisture, sun and wear out of timber, and comes in two forms: a penetrating oil that soaks in and seals from within, or a surface film like varnish that seals with a hard clear coat. For a natural, low-maintenance seal, Premium Wood Oil penetrates and protects; for a hard, glossy sealed film, Glossy Wood Copal Varnish seals the surface. This guide explains what a wood sealer does, which type to use, and how to apply it.
What is the best thing to seal wood?
The best wood sealer depends on the wood and the look: a penetrating oil for decks, new timber and a natural finish, or a varnish film for a hard, glossy sealed surface. On decks, garden furniture and new wood, a penetrating Premium Wood Oil seals from within, flexes with the timber and is easy to refresh. On doors, furniture and trim where you want a tough clear film, Wood Copal Varnish seals the surface with a durable gloss. Match the sealer to how the wood is used.
What is a wood sealer used for?
A wood sealer is used to keep water, ultraviolet (UV) sun, dirt and wear out of timber, so it does not dry out, grey, crack, warp or rot. Untreated wood absorbs moisture and swells and shrinks with the weather, and UV bleaches and breaks down the surface. A sealer — whether a penetrating oil or a varnish film — blocks that moisture and UV, keeps the wood dimensionally stable, and preserves its colour and strength. On outdoor timber especially, sealing is what stands between the wood and the weather.
What is the difference between a wood sealer and a wood finish?
"Sealer" describes the protective job — keeping moisture and UV out — while "finish" describes the look; most modern products do both in one. A penetrating Premium Wood Oil seals and finishes at once, feeding the wood and leaving a natural look. A Wood Copal Varnish seals and finishes with a glossy film. So you rarely need a separate sealer and topcoat on these products — the oil or varnish is the seal and the finish together.
Penetrating sealer or film sealer?
A penetrating sealer (oil) soaks into the wood and never peels; a film sealer (varnish) sits on top as a hard coat that can eventually crack or peel if neglected. The penetrating oil is the low-maintenance option — it wears thin gradually and you just re-oil, with no stripping. The film varnish gives a harder, glossier, more wipeable surface, better for indoor furniture and doors, but it needs sanding back if it ever fails. Choose penetrating for decks and outdoor timber, film for hard indoor surfaces.
What sealer works for exterior and coastal wood?
Exterior and coastal timber is best sealed with a penetrating, UV-resistant wood oil, which flexes with the wood and is easy to top up as sun and salt wear it. Outdoor wood takes the full brunt of sun, rain and, near the coast, salt air, which quickly defeats a rigid film. Premium Wood Oil penetrates and gives UV protection while staying flexible, so a coastal deck or gate stays protected with a simple clean-and-recoat. For a glossy exterior door specifically, an exterior-grade Wood Copal Varnish film is the alternative where the look matters more than easy maintenance.
Does a wood sealer make wood waterproof?
A wood sealer makes timber highly water-resistant and stops it soaking up moisture, but wood is a natural material that still moves, so it is water-repellent rather than fully waterproof. A good oil or varnish sheds rain and keeps the wood from swelling and rotting, which is what matters for decks, furniture and doors. It does not turn timber into a waterproof membrane, and it needs maintaining as it wears — an unrefreshed sealer eventually lets water back in. Keep the coat sound and the wood stays protected.
How do you apply a wood sealer?
Clean and dry the wood, sand it smooth, then apply the sealer along the grain — flooding on oil and wiping back the excess, or brushing varnish in thin even coats. Strip off any failed old coating, sand weathered or new timber to a clean, keyed surface, and remove the dust. For Premium Wood Oil, apply generously, let it soak in and wipe off the surplus; for Wood Copal Varnish, brush thin coats along the grain and sand lightly between them. Work in dry, mild conditions and keep new work out of rain until it has cured.
How many coats of sealer does wood need?
Penetrating oil needs coats until the wood stops absorbing it — usually two indoors and more on thirsty new or exterior timber; a varnish film needs two to three thin coats. New and outdoor wood drinks the first coats of oil, so keep going until the surface stays satiny rather than soaking in. Varnish builds with each coat, so three coats give the fullest, hardest gloss. Let each coat dry to the recoat time before the next.
How do you maintain a sealed wood surface?
Keep it sealed by recoating before the finish fails: clean and re-oil an oiled surface when it dulls, and sand-and-recoat a varnish film if it starts to crack. An oiled deck or table is simple — wash it, let it dry and apply a fresh coat, no stripping. A varnished surface lasts well indoors but needs attention outdoors as UV works on the film. Recoating on schedule, before the wood greys or water stops beading, is far less work than restoring bare, weathered timber. See when and how to re-seal wood.
Where to buy
Shop Premium Wood Oil and Glossy Wood Copal Varnish with national delivery, or visit our paint shops in Table View, Cape Town and Edenvale, Johannesburg. For advice, call +27 84 985 6141. See the full wood finish guide.
