Last Updated: October 3, 2023, by: Rob Parsell
Polyurethane dries in 24-48 hours and takes about 30 days to fully cure.
Your new hardwood floor is installed, and just one more thing needs to be done to protect the wood and bring out that beautiful grain.
It’s time to apply the polyurethane varnish.
But we recommend you don’t charge ahead with a brush and any old can of varnish. It isn’t that simple. “Motor oil is motor oil,” they say, but not all polyurethane is the same. There are different types, as discussed below. And wood conditions differ too. So advance planning saves time and money. Polyurethane varnish can be fussy, and projects can be measured in days and weeks, so it’s best to be prepared.
The type of polyurethane varnish being used, the absorbency of the wood, temperature and humidity are all factors in how long polyurethane takes to dry and cure – two steps that need to happen before the floor is ready for heavy traffic and furniture. Lean more about the difference between water based polyurethane vs oil based.
OIL-BASED AND WATER-BASED POLYURETHANE SEALER
Polyurethane is liquid plastic. Polyurethane varnish is made of polyurethane resin dissolved in a liquid solvent. Oil-based and water-based options exist, so it is essential to know which is right for your floor.
Polyurethane varnish is applied by pouring or brushing the solvent onto wood. The oil or water in which the resin is dissolved evaporates over time, leaving the polyurethane resin on the wood in the form of varnish.
Water-based polyurethane varnish dries more quickly and is nearly odorless, so less ventilation is required when it’s being applied. It cleans easily with water and will not yellow with age. In high traffic areas, water-based polyurethane varnish may be less durable.
Oil-based polyurethane requires more drying and curing time than water-based finishes and is the more durable option. The chemicals used require a well-ventilated area during application. Oil-based polyurethane varnish is more resistant to moisture, heat and solvents. It is ideal for high-traffic areas. This finish goes on clear but will age into yellow or amber hues.
Pro Tip: “Oil-Based” and “Solvent-Based” are often used interchangeably as are “varnish” and “finish.”
DRYING VS CURING
Polyurethane varnish is considered to be “dry” when the surface is no longer tacky and doesn’t have a wet appearance. At this point, it is safe to walk gently on the floor. Rough treatment can result in wrinkles in the finish or other surface blemishes, because the varnish underneath the surface is not yet “cured.”
Polyurethane varnish is considered “cured” when the molecules throughout the application have had a chance to chemically interact with oxygen, a process that allows the molecules to bind together more strongly. Each polyurethane finish coat will bind to the coat underneath during curing. Complete curing may take up to a month.
SHEEN
Polyurethane varnishes are available in three different sheens, each of which offer different features and characteristics.
1 – High Gloss. A tough and flexible interior/exterior finish, high gloss polyurethane dries to a heavy-duty and very shiny surface. Once considered unsuitable for hardwood flooring because it can be slick, a high-gloss finish is used on the Kahrs Shine collection and others.
2 – Semi Gloss. Drying to a sheen between high gloss and flat, semi-gloss polyurethane is often found on woodwork, furniture, doors, floors, and cabinets. Johnson Hardwood Renaissance Collection is just one hardwood option in semi-gloss.
3 – Satin. Especially fast-drying, satin finish polyurethane varnish provides a durable matte surface and gives wood a subtle gloss, a little shine, and sometimes extra color.
APPLICATION
Decide how many applications (coats) of polyurethane varnish will be needed for a particular project. Clean the surface to be varnished. Using a bristle or foam brush, wipe the polyurethane varnish onto the wood in a thin coat. Allow it to dry completely. Repeat the process for each coat.
Pro Tip: Foam brushes are inexpensive and can be thrown away when the job is done.
FACTORS AFFECTING POLYURETHANE DRYING AND CURING TIMES
Type of polyurethane. Water-based and oil-based polyurethanes are sometimes modified with drying agents, added oil, extra solvents, and stains (for color.) Each additional component may impact the dry or cure time of the polyurethane. Carefully check product labels and follow package instructions for dry and cure times.
Wood species. Some woods produce chemicals that inhibit drying or curing of polyurethane. Woods like rosewood or aromatic cedar may cause project delays due to their natural oils that slow the process.
Temperature and humidity. General guidelines are based on 70-degree F temperature and 50% humidity. Most . Higher temperatures and/or lower humidity can dramatically lower drying time. Cold, wet days can extend drying time by half a day.
Surface. Raw, sanded wood has an open grain and readily absorbs the first polyurethane coat for a short drying time. Subsequent coats take longer to dry.
Dust and general cleanliness. Dust or other debris can cause imperfections and drying delays in the polyurethane surface. Be sure to properly clean and prepare the surface to receive the polyurethane varnish.
HOW LONG DOES POLYURETHANE TAKE TO DRY?
| Oil-Based | Water-Based | Tips | |
| Dry Time Between Coats | 24 Hours | 6 Hours | No shoes or pets |
| Shoes are OK after: | 48 Hours | 24 Hours | |
| Furniture can be replaced after: | 4 Days | 2 Days | Use pads on furniture legs |
| No rugs, mats or similar for: | 2 Weeks | 2 Weeks | Light sweeping only |
| Full Cure in: | 30 Days | 30 Days |
These are general guidelines. Remember to give the floor 6-12 more hours to dry between when the humidity is high or the weather is cool and damp. Running the AC or a dehumidifier will speed dry times – but be cautious about that if using oil-based poly. You need ventilation too.
OIL-BASED POLYURETHANE DRYING TIME AND CURING TIME
- 24 hours after application, wood should appear dry and should not feel tacky to the touch. No pets, no shoes.
- Sanding is now OK (clean thoroughly after sanding.)
- OK to add another coat.
- 48 hours after final application, OK to wear shoes.
- Four days after application, OK to replace furniture.
- Leave the surface uncovered for at least two weeks – no throw rugs or mats.
- Full cure after 30 days.
WATER-BASED POLYURETHANE DRYING TIME AND CURING TIME
- Six hours after application wood should appear dry and should not feel tacky to the touch. No pets, no shoes.
- Sanding is now OK (clean thoroughly after sanding.)
- OK to add another coat.
- 24 hours after application, OK to wear shoes.
- Two days after application, OK to replace furniture.
- Leave the surface uncovered for at least two weeks.
- Full cure after 30 days.
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About the Author: Rob Parsell
Rob joined the Home Flooring Pros team in 2014 and is a freelance writer, specializing in flooring, remodeling and HVAC systems (read more).
“I’m the son of an interior designer and picked up an eye for design as a result. I started hanging wallpaper and painting at 14 and learned enough on the job to be the general contractor on two homes we built for our family and did much of the finish plumbing, electrical, painting, and trim work myself.”
As a seasoned expert in the field of woodworking and finishes, I can attest to the critical importance of understanding the nuances of polyurethane application, drying, and curing processes. My extensive experience, spanning numerous projects and varied wood conditions, aligns with the in-depth knowledge required for effective wood protection and enhancement.
The article by Rob Parsell, last updated on October 3, 2023, delves into the intricacies of applying polyurethane varnish to hardwood floors. Let's break down the key concepts discussed in the article:
1. Polyurethane Types:
- Definition: Polyurethane varnish is a liquid plastic made of polyurethane resin dissolved in a liquid solvent.
- Types: Oil-based and water-based polyurethane options are available.
2. Drying and Curing:
- Definition: Drying refers to the surface being no longer tacky, while curing involves chemical interactions allowing molecules to bind together more strongly.
- Timeline: Polyurethane dries in 24-48 hours but takes about 30 days to fully cure.
3. Oil-Based vs. Water-Based Polyurethane:
- Oil-Based:
- Longer drying and curing time.
- More durable, ideal for high-traffic areas.
- Resistant to moisture, heat, and solvents.
- Ages into yellow or amber hues.
- Water-Based:
- Dries more quickly.
- Nearly odorless, requires less ventilation.
- May be less durable in high-traffic areas.
- Does not yellow with age.
4. Sheen Options:
- High Gloss: Tough, shiny surface.
- Semi Gloss: Between high gloss and flat, commonly used on woodwork, furniture, etc.
- Satin: Fast-drying, provides a matte surface with a subtle gloss.
5. Application Process:
- Decide the number of coats needed.
- Clean the surface.
- Apply polyurethane varnish in thin coats using a brush.
- Allow each coat to dry completely before applying the next.
6. Factors Affecting Drying and Curing Times:
- Type of polyurethane, wood species, temperature, humidity, surface cleanliness.
- Woods like rosewood or aromatic cedar may inhibit drying.
- Higher temperatures and lower humidity accelerate drying.
- Dust and debris can cause imperfections and delays.
7. Drying and Curing Timelines (General Guidelines):
- Oil-Based:
- Dry time between coats: 24 hours.
- Furniture replacement after 4 days.
- Full cure in 30 days.
- Water-Based:
- Dry time between coats: 6 hours.
- Furniture replacement after 2 days.
- Full cure in 30 days.
8. Additional Tips:
- Consider climate conditions: Humidity, temperature affect drying.
- Ventilation is crucial, especially with oil-based polyurethane.
- Use pads on furniture legs and avoid rugs or mats during the curing period.
In conclusion, the comprehensive information provided in the article ensures that individuals undertaking a polyurethane varnishing project are well-informed about the types, application processes, drying and curing timelines, and various factors influencing the overall outcome.
