The Difference Between Polyurethane and Natural Wood Sealers
If you're building raised garden beds, protecting a fence, or finishing a pergola, chances are you've already spent time picking up the right wood. But have you given much thought to what you're going to seal it with?
Many homeowners reach polyurethane wood sealer almost out of habit. It's one of the most widely available finishes out there, and it's been protecting furniture, floors, and outdoor builds for decades now. Part of that comes down to durability. Part of it is water resistance.
But not every job calls for the same finish. A coating that works beautifully on hardwood flooring can fall short in a vegetable garden or a backyard living space. Weighing polyurethane against a natural wood sealer? It helps to know how each one actually works before you commit to one.
What Is Polyurethane?
Polyurethane is a synthetic plastic polymer. Most of them are made from petroleum-derived chemicals. Once it's brushed onto wood and left to cure, it hardens into a coating that sits right on top of the surface, sort of like a clear plastic shell.
You'll typically find it used on:
(1) Hardwood floors
(2) Indoor furniture
(3) Cabinets
(4) Doors
(5) Trim
(6) Outdoor furniture
(7) Decks
Its main selling point is that the hard barrier it leaves behind. Scratches, stains, and moisture hold up well against all of it.
How Polyurethane Protects Wood
Polyurethane doesn't soak into wood the way a penetrating sealer does. It lays a film across the top instead.
That film offers protection against:
(1) Water
(2) Dirt
(3) Surface scratches
(4) Everyday wear
(5) Minor stains
Indoors, that works out fine. The finish isn't dealing with much more than stable temperatures and everyday use.
Outside is a different story. Wood expands and contracts as temperatures and moisture swing through the seasons. Years of sun, rain, and snow take their toll, and eventually a polyurethane coating starts to crack, peel, or flake. Once that happens, moisture works its way down to the wood underneath.
How Natural Wood Sealers Work
Natural wood sealer goes about it differently. There's no plastic film sitting on top. They soak into the wood fibers themselves, which cuts down on water absorption and lets the wood hang onto its natural look.
There's no thick coating to fight with later, either, so upkeep is usually painless. No sanding off an old finish before redoing it, just clean the wood and add another coat whenever it needs one. That's probably why so many people lean toward natural oil-based finishes for outdoor work.
Why Seal It Green Is Different
At Seal It Green, we don't think wood needs a petroleum-based synthetic coating to stay protected.
Our sealer is built from 100% plant-based natural oils, with natural essential oils added in.
Seal It Green doesn't form a plastic film over the wood. It works its way deep into the fibers instead, so you get lasting water protection without losing the wood's natural character.
Here's what goes into our formula:
(1) 100% plant-based natural oils
(2) No petroleum-based ingredients
(3) No synthetic plastic polymers
(4) Natural essential oils
Whether you're working on raised garden beds, planter boxes, pergolas, fences, or outdoor furniture, Seal It Green gives you a natural option outside of the usual polyurethane finishes.
Polyurethane vs. Seal It Green
Polyurethane
(1) Forms a hard protective plastic film on the wood
(2) Made from petroleum-derived synthetic polymers
(3) Excellent scratch resistance
(4) Commonly used on floors, furniture, and cabinets
(5) May crack or peel as outdoor wood expands and contracts
(6) Refinishing often requires sanding before reapplication
Seal It Green
(1) Penetrates deep into the wood fibers
(2) Made from 100% plant-based natural oils
(3) Contains no petroleum-based synthetic polymers
(4) Naturally scented with essential oils
(5) Easy to maintain with a simple cleaning and reapplication
(6) Ideal for raised garden beds, fences, pergolas, and outdoor wood protection
Why Ingredients Matter
Homeowners today pay closer attention to what they're bringing into their yards. Natural mulch. Organic soil. Untreated wood. Eco-friendly cleaners. It's the same mindset, just applied to wood finishes now too.
Polyurethane leans on petroleum-based synthetic polymers that harden into a durable plastic layer. Seal It Green does it another way of plant-based oils that sink into the wood instead of sealing it under plastic.
For a lot of homeowners, especially anyone growing vegetables or building a pollinator-friendly yard, that distinction really matters.
What About Microplastics?
Microplastics has become a bigger focus in scientific research lately. Studies keep digging into how plastic weather breaks down in the environment.
Polyurethane is a synthetic plastic polymer, so it's not exempt from that. Years of sun, rain, temperature swings, and everyday wear will age it, same as any other plastic material. Researchers are still sorting out exactly how much weathering contributes to microplastic pollution in soil and waterways.
Seal It Green takes a different path.
Our sealer is made entirely from plant-based natural oils, so there's no synthetic plastic polymer in it at all. No plastic coating sitting on the wood. Nothing there to eventually break down into plastic particles.
For homeowners trying to cut back on petroleum-based plastic in their gardens, that difference can matter quite a bit.
Application and Safety
There's another difference worth mentioning what you're actually putting on the wood in the first place.
Many polyurethane products contain petroleum-derived ingredients. Depending on the formula, they may also carry solvents or other reactive chemicals that need careful handling. That's why labels often call for gloves, good ventilation, and keeping the stuff off your skin and out of your eyes until it's fully cured.
Seal It Green, on the other hand, is built from plant-based natural oils.
It also includes natural, essential oils.
It's designed for homeowners who'd rather protect their outdoor wood without relying on harsh chemicals.
Of course, no matter which finish you choose, it's always worth reading and following the manufacturer's instructions.
Which Wood Sealer Is Right for You?
Every project has its own quirks, its own demands.
If you're working on hardwood floors, cabinets, or furniture where scratch resistance is the top priority, polyurethane is probably still the better fit.
But if you're protecting:
(1) Raised garden beds
(2) Vegetable gardens
(3) Planter boxes
(4) Pergolas
(5) Fences
(6) Chicken coops
(7) Outdoor furniture
A penetrating, plant-based sealer like Seal It Green gives you a natural alternative that protects the wood without wrapping it in synthetic plastic.
Protect Your Outdoor Wood from Weather Damage
Final Thoughts
No single wood sealer is the right fit for every project. Polyurethane has earned its reputation as one of the toughest finishes around for indoor surfaces that see a lot of wear.
But for outdoor projects, gardens especially, many homeowners are drawn to materials that feel closer to nature, and that's where a penetrating, plant-based sealer comes in.
Seal It Green is made from 100% plant-based natural oils, skips the petroleum-based synthetic polymer altogether, and protects wood by soaking into the fibers rather than covering them in plastic.
Whether you're preserving a raised garden bed, protecting a pergola, or helping an outdoor fence last longer, picking up the right wood sealer can keep your project looking good for years to come.
Frequently Asked Questions
1. What's the main difference between polyurethane and a natural wood sealer?
Polyurethane sits on top of the woods. It's a synthetic plastic polymer that cures into a hard film over the surface. A natural wood sealer does the opposite. It soaks into the fibers rather than coating them, and that's really why the two hold up so differently once you take them outdoors.
2. Is polyurethane wood sealer good for outdoor wood protection?
Sometimes, but not always. Outdoor wood expands and contracts as the weather changes, and that movement wears a polyurethane coating over the years. Eventually it can crack, peel, or flake, and once it does, moisture gets straight to the wood underneath. Raised garden beds, fences, pergolas, a penetrating wood sealer usually fares better on things like that over the long haul.
3. Can I use polyurethane on a raised garden bed or planter boxes?
Technically, yes. Most people skip it anyway. Polyurethane is petroleum-based, and it can shed microplastics as it weathers, so a lot of homeowners growing vegetables or keeping a pollinator-friendly yard go with something plant-based instead, like Seal It Green.
4. Is a natural wood sealer as water resistant as polyurethane?
Yes, just through a different mechanism. It soaks into the wood fibers and cuts water absorption from the inside out, so there's no need for a surface film to get the same water resistance. Different approaches, same result.
5. Do I need to sand before reappearing a wood finish?
Depending on the finish. With polyurethane, usually you're recoating over an existing plastic layer, so sanding is part of the process. A natural wood sealer doesn't ask for that. Clean the wood, add another coat when it needs one, and you're done.
