For those using polyurethane as a finisher for wood, you may have many questions — especially if this is your first time. People often wonder how long you need to wait for the poly to dry or how long it takes for polyurethane to completely cure? Don’t worry! We have the answers that you’ll need below.
The short answer: While polyurethane can dry in only a few hours, you’ll want to allow it to cure past contact dry before applying more poly or a wax coating. It can take polyurethane up to 30 days to fully cure; however, allowing 1-2 days should be long enough to keep you from running into any issues.
What is Polyurethane, and How Do I Apply It?
Polyurethane is a synthetic polymer made of organic urethane groups. While mainly used as a finishing layer for wood, it can also be used as a foam to act as a supporting agent for furniture. By applying polyurethane to your project, you protect it against scratches and water damage. Plus, you will give it a nice glossy finish bringing out a deeper color signature.
Use a fine brush or rag to get a thin coating onto the wood to apply polyurethane properly. Ensure that you are moving along the grain. Going against the grain during polyurethane application means there is a chance that you can raise it. It can also lead to an uneven coating.
If you’re new to working with polyurethane ensure that you’re using it correctly as per manufacturers directions, and follow their safety data sheet.
How Much Polyurethane Should I Apply?
The amount of polyurethane you apply will depend on what kind you are using. Polyurethane can be water-based or oil-based, and there are big differences between the two.
Water-based polyurethane is thinner than its oil-based counterpart. While it dries quickly and does not have such strong fumes, it is weaker, more expensive, and requires at least four coatings for it to be effective. Additionally, wood treated with water-based polyurethane should be re-treated roughly every two years.
Oil-based polyurethane is a thicker solution, meaning it takes longer to dry. While it does emit fumes, it is more effective at protecting the wood while also offering a darker color finish. Due to it being thicker than the water-based finisher, you will only need to apply around two coats to be efficient. (Although you may need more if you are light-handed with your poly!)
How Long Should I Wait Between Polyurethane Coats?
The ideal time to wait in between coats is about two hours. Adding coats promptly means any dust or particles that found their way into your poly won’t need to be sanded until the final coat is applied.
However, if you take your time, and more than twenty-four hours have passed before the last layer being applied, then the most recent layer will need to be sanded properly.
In simpler terms, layers applied to each other within two hours will form a chemical bond, while layers several hours old will need to be sanded down for a mechanical bond to be developed. With sometimes upwards of four to six layers required to get a proper coating, it is best to begin applying when you have an adequate time bank to save yourself unnecessary sanding.
How Long Before the Polyurethane Smell Goes Away?
The polyurethane smell should go away naturally anywhere from five to seven days after applying. However, faint scents can always linger around in your home for up to a month — especially if the odor seeps into carpet or furniture.
A good way to prevent this is by opening windows and turning on fans to promote constant circulation of the smelly air.
Should I Wax After Polyurethane? Can Polyurethane be Properly Waxed?
After polyurethane has had the proper time to cure, it would be optimal to apply a wax coating on top. To get a fully cured workpiece, it is best to wait roughly three to four weeks before applying a wax coating.
Pro Tip: Paste wax is the best option for polyurethane finishes. It adds another depth of color and beauty and fills minor scratches while preventing new ones.
Adding wax will further reinforce the polyurethane and protect your handiwork more efficiently. You must work in the direction of the grain when applying the paste wax. This technique not only applies a more even coating but also covers any fine scratches that may not be easily visible.
How Long Should Polyurethane Dry Before Waxing?
If you are looking to apply wax immediately after drying, you will need to wait around four to six hours rather than waiting for a complete cure. However, if you have more time on your hands, then waiting up to a whole week would be a much safer choice.
While it isn’t nearly enough time for a complete cure, the polyurethane will have at least some time to settle and develop properly.
