Polyurethane was invented in the 1930s and can be found in both liquid and solid forms, including insulation, sportswear, adhesives and coatings. It is a type of varnish that provides better protection against water, impacts and other solvents than traditional varnish.
Water-based polyurethane was introduced in the 1990s and found immediate acceptance among flooring specialists, painters and homeowners due to its low odor, reliable performance and ability to stay clear for years after application. What is the best choice for your floor finish? Let’s discuss the features and benefits of interior and exterior water-based polyurethanes and how they should be applied.
Water vs. Oil-Based Polyurethane Finish
Water and oil-based polyurethane finishes are both extremely durable finishes for flooring. However, there are a few differences worth noting:
Oil-based products usually contain higher VOCs and need to be applied when sufficient ventilation is available.
Only two coats are required with an oil-based polyurethane. Three coats may be recommended when using water-based products on floors.
Dry times for oil-based could be extended. For instance, water-based polyurethane could need two hours between coats and oil-based could need up to 24 hours between coats.
Water-based polyurethane cleans up easily with soap and water.
Most oil-based finishes will give a yellow or amber tone to the wood, which is why water-based polyurethanes are also recommended for light woods or over light-colored stains.
Selecting the Correct Finish for Exterior vs. Interior Applications
When it comes to applications, it is important that exterior polyurethane be used on the exterior and interior polyurethane be used on the interior. Exterior polyurethane contains UV absorbers that need direct sunlight to properly cure. However, exterior products could be applied inside if the desired area is exposed to direct sunlight for the majority of the day. Exterior polyurethane will also flex better when the wood surface expands and contracts due to weather and temperature changes.
The Best Interior Water-Based Polyurethane Finish Option
ZAR® Interior Water Base Poly Crystal Clear is a clear protective coat recommended for light bare wood or light stain colors. It is environmentally safe and non-yellowing, so you can use it with confidence to protect your interior wood projects. ZAR® Poly is approved for exotic hardwoods and recommended for Teak, Brazilian Walnut and similar species.
Which Interior Surfaces Can the Finish Be Used On?
Crystal clear poly is recommended for use on wood cabinets, furniture, interior wood siding and wood floors. It dries very quickly and provides a tough finish that will stand up to the everyday use of a modern home.
How To Apply Water-Based Polyurethane Indoors
Preparing the Surface
Any surface to be covered must be completely dry, free of grease, dust, oil and stains. Here are some general preparation guidelines to follow:
Stir the contents of the can — do not shake!
Sand smooth using fine sandpaper and then vacuum any sanding dust. Wipe using a tack cloth to remove any remnants of dust prior to application.
Do not use steel wool.
If open-grained woods are to be filled, use a filler that does not contain stearates or waxes, such as ZAR® Patch Wood Filler or ZAR® Trowelable Wood Patch.
For old finishes in good shape, make sure all wax, grease and dirt are removed.
Old finishes in bad condition should be removed completely.
Applying the Polyurethane
The contents appear milky when first applied, but will dry clear.
Always test an inconspicuous area first to ensure great results.
Stir the contents of the can — do not shake.
Use a synthetic fiber or foam brush.
Do not use a roller.
Apply in thin coats to avoid bubbles and drips.
Check finish yearly for signs of wear.
Special Instructions for Floors:
Follow the general guidelines above. If the floor is to be stained, follow the manufacturer’s directions. Specific directions to be followed:
Areas with poor ventilation, such as closed rooms, corners and hallways, may take longer to dry.
Apply ZAR® Interior Water Base Poly Crystal Clear using a brush, synthetic applicator or pad. A minimum of three coats is required.
Allow floors to dry for 24 hours before subjecting them to light foot traffic. Let them dry for three to five days before allowing moderate traffic or placing furniture.
One week is required before maximum hardness is achieved. Do not cover floors with rugs before a week has elapsed. If the floor should become marred or scratched, sand lightly using fine sandpaper. Vacuum any sanding dust, wipe with a cloth dampened with water and apply another coat.
The Best Exterior Water-Based Polyurethane Finish Option
The best exterior water-based polyurethanes are environmentally safe, have additives to absorb the UV rays of the sun, protect against harsh weather conditions and contain antioxidants to protect the finish. In addition, the best exterior water-based poly should be compatible with multiple surfaces. ZAR® Water Base Poly Exterior HP provides protection and flexibility.
Which Exterior Surfaces Can the Finish Be Used On?
ZAR® Water Base Poly Exterior HP can be used on most exterior surfaces. Unlike other brands, ZAR® is a premium product approved for use on wood, metal and fiberglass — anywhere a durable, clear finish coat is desired. ZAR® can be used on marine surfaces above the waterline.
How To Apply Water-Based Polyurethane Outdoors
Preparing the Surface
Any surface to be covered must be completely dry, free of grease, dust, oil and stains. Here are some general preparation guidelines to follow:
Do not use it on painted surfaces.
If you are using on stained doors that have not been covered with ZAR®, do not sand first.
Apply when air and surface temperatures are between 60 – 90℉.
When covering old clear surfaces, make sure all grease, dirt and wax are removed, then lightly sand in the direction of the grain to remove any gloss.
Old clear surfaces in poor condition should be completely removed, but do not use steel wool.
Applying the Polyurethane
The contents will appear milky when first applied but will dry to a rich amber color.
Always test an inconspicuous area first to ensure excellent results.
Stir the contents of the can but do not shake.
Use a synthetic fiber or foam brush.
Do not use a roller.
Apply in thin coats to avoid bubbles and drips.
Check finish yearly for signs of wear.
How To Select the Best Water-Based Polyurethane Finish for Your Project
ZAR® Premium Finishes is part of United Gilsonite Laboratories, which has been developing industry-leading interior and exterior coatings for 85 years. We use the finest resins in our finishes, and our commitment to quality extends to the DIYer as well as the professional contractor.
Our water-based finishes provide the beauty of oil base stains with the environmental benefits of a water-based product. ZAR® ‘s water-based stains and finishes meet all environmental standards for low emissions of solvent vapors. Check out our website for product guides, safety data sheets and how-to videos. Contact us today to find a ZAR® dealer near you.
