Seal-Once NANO+POLY Penetrating Wood Sealer with Polyurethane - 1 Gallon. Water-based, Low-VOC, waterproofer & stain for decks, fences & log homes.

What I used it on

I put the Nano+Poly sealer to work on two very different projects: a weathered cedar deck and a pair of bare pine patio benches. I stuck with the clear version because I wanted to keep the natural tone of the wood and see grain rather than lay down a pigment. My goals were straightforward—tighten up moisture resistance on a horizontal surface that sees rain and snow, and make the benches wipe-clean without changing their look.

Prep and application

Prep matters more with this product than with many film-forming finishes. On the deck, I did a thorough clean and rinse, then let it dry until the moisture meter read safe for sealing. On the benches, I did a light sanding to knock down fuzz and open the pores; dust was vacuumed and wiped away with a damp cloth so the sealer could penetrate evenly.

The first thing you notice is the consistency—it’s closer to water than to a typical polyurethane. That’s a plus for penetration and cleanup, but it changes your technique. I stirred well, then strained it into a tray to catch any minor settling. A synthetic brush and a small roller both worked, but the brush was better for working it into end grain, checks, and joints.

The most important instruction with Nano+Poly is the recoat window. The second coat has to go on while the first is still damp. In cool, overcast conditions, that gave me roughly 20–30 minutes. In warm sun, the window shrank noticeably. On the deck I worked in small, reachable sections to keep a live edge; on the benches I had a second set of hands ready so one of us could follow with coat two immediately. If you miss that window, the second coat tends to bead and won’t soak in. Plan your workflow with that in mind—don’t bite off a whole deck bay if you can’t get back to it fast enough.

Expect drips when you’re working above waist height. The thin viscosity is a double-edged sword: it penetrates beautifully, but it will run if you overload the brush. When I moved to railings and the underside of the benches, I switched to lighter loads and a slower pace. A pump sprayer would be faster for large runs of fencing or siding, but you’ll still want to back-brush to work it in and catch sags.

Cleanup is easy with soap and water, and the odor is minimal. That’s a big advantage if you’re sealing in an attached space or around living areas.

Coverage and efficiency

Coverage was generous. A gallon went further than I expected across both projects with two wet-on-wet coats. On thirsty end grain and older boards, the first coat disappears quickly—that’s what you want—so be ready to feed those areas a little more. On the benches, the second coat took less; by that point the surface stayed uniformly damp without dry spots flashing off.

If you’re using a tinted version, give it an extra-thorough mix to bring any settling back into suspension. With clear, I didn’t encounter any stubborn sludge, but I still stir before every pour.

Finish and appearance

Clear Nano+Poly dries with a low-sheen, natural look that preserves grain definition. While wet, there’s a slight milky cast, but it flashes off as it dries. On the cedar deck, the finish didn’t amber or cloud the color; on the pine benches, it kept the light tone and provided a more uniform look by filling micro-checks. Because this is a penetrating sealer with polyurethane, you don’t get a plastic film or heavy gloss—something I prefer for exterior wood that expands and contracts.

Knots and dense latewood sections can absorb differently, especially on softwoods. With clear, any minor variation is subtle. If you’re chasing a perfectly even appearance, a pigmented version will even things out, but you’ll still want to test on a scrap to see how knots take color.

Water repellency and day-to-day performance

Water beading was immediate and dramatic after curing. Rain stood up on the deck rather than soaking in, and the benches went from “perpetual dust catchers” to “wipe-clean in seconds.” What I care about more than pretty beads is whether the wood stays dry beneath the surface, and here the penetrating aspect helps. Even after the most aggressive hose test, boards dried quickly without dark, damp halos.

Underfoot, the deck didn’t feel slick once fully cured. I gave it two days before heavy use. Early scuffs and traffic didn’t lift or smudge the finish because there isn’t a brittle film at the surface. That’s a major advantage of a penetrating system for high-traffic, horizontal applications.

Durability so far

Exterior finishes live and die by two factors: exposure and prep. On the vertical bench legs and rail posts, Nano+Poly shows almost no change after months outdoors. On horizontal deck boards, the top surfaces always take the brunt of UV and standing water. After a full weather cycle, water repellency was still strong on the majority of the deck, with a few high-traffic spots softening first. That’s normal for horizontal surfaces. The benefit of a penetrating sealer is that touch-ups don’t require stripping a film—clean, let dry, and reapply wet-on-wet where needed.

If you work in a region with freeze-thaw and long winters, plan on more frequent maintenance for flat surfaces. Vertical fences and siding typically go much longer between refreshes.

One caution: this is a water-based product and can be ruined by freezing during storage or transport. If it arrives gelled or curdled, don’t use it. Keep it above freezing and sealed between projects.

What I liked

• Low-VOC, low odor, water cleanup
• Penetrates well; doesn’t leave a brittle film
• Natural, clear look that preserves grain
• Excellent water repellency immediately after cure
• Generous coverage for a two-coat system
• Brush- or sprayer-friendly, with easy back-brushing

What could be better

• Tight recoat window demands planning, especially in warm, dry weather
• Thin viscosity drips on overhead or vertical work if you overload the brush
• Horizontal durability will still require periodic touch-ups in harsh climates
• Any settling in tinted versions requires careful mixing

Tips for success

• Prep thoroughly: clean, rinse, and let wood dry; sand lightly on new or fuzzy surfaces.
• Work in sections you can recoat within 15–30 minutes. Keep a live edge to avoid lap marks.
• Prioritize end grain and checks on the first coat; feed those areas more product.
• Avoid hot midday sun and wind; aim for cooler parts of the day to extend your wet-on-wet window.
• Back-brush after spraying to push the sealer into the fibers and catch runs.
• Let it cure before heavy traffic; then build maintenance into your seasonal routine.

Who it’s for

If you value a natural look, low odor, and easy maintenance, Nano+Poly fits well. It’s especially good for softwoods, cedar, and pressure-treated lumber where you want moisture protection without a film that can peel. It’s also a smart choice for vertical applications—fences, siding, log and timber elements—where penetration and breathability pay off with longer intervals between refreshes.

If you want a heavy, glossy build or a single-coat, set-and-forget film for a sunbaked, high-traffic deck, this isn’t that product; you’ll be happier with a more robust film-forming system and the sanding that comes with it.

Recommendation

I recommend Nano+Poly for homeowners and pros who prioritize a low-VOC, penetrating exterior sealer that keeps wood looking like wood and simplifies maintenance. It excels when you respect its wet-on-wet recoat window and commit to good prep. Expect outstanding water repellency out of the gate, a natural finish that won’t peel, and straightforward touch-ups down the line—especially on vertical surfaces. On horizontal decks in harsh climates, plan for periodic maintenance rather than multi-year neglect, and you’ll be satisfied with the protection and appearance it delivers.