Sometimes it can happen that the oil-based polyurethane does not dry well. This does not probably really means it is a bad polyurethane. It is more likely that the wood you are working on contains natural oil, or perhaps you have applied oil to the wood, and it has not dried.
In both cases, it has to do with only the first layer of polyurethane. Once the first coat is dry, no additional drying problems should occur.
Nevertheless many exotic kinds of wood ( jungle wood), excluding mahogany, contain natural resin, which is very greasy. You can feel the greasiness when you touch wood. The solvent of mineral spirits in polyurethane is also the solvent of the resin.
So when you apply polyurethane on bare wood, the polyurethane mixture and the oily resin slow down the drying of the polyurethane. The same explanation applies to the situation with the application of polyurethane on linseed or other oil until this oil is completely dry.
If after you’ve applied polyurethane and it doesn’t dry, then you can try using heat, for instance, from a heat lamp or hairdryer. This will speed up drying, though not by much. You may need to remove the polyurethane with a strong solvent like varnish or acetone thinner or strip of paint and start over.
How Long should You wait for the Coat of Polyurethane to dry?
In the case of wood flooring, it reaches its maximum durability after up to 4 weeks, depending on weather conditions (e.g., heat, humidity, etc.) and the thickness of the polyurethane coatings. Until you don’t smell the odor given off by the surface, it shows it is still curing.
Sometimes nothing is wrong except for the fact you are impatient. You must understand that the finish layer dries in two phases. First, the thinner will evaporate, and will not feel sticky when you touch the surface.
However, oxygen exposure then triggers the varnish curing process. This is the second stage when the woodwork is completely dry and hard.
What to do when Polyurethane doesn’t dry? The Ultimate Solution
Why is the varnish not drying after following all of the application processes accordingly? If the polyurethane still feels sticky after two days ( 48 hours), the wood likely contains natural oil that is preventing it from drying out.
Most of the time, when the situation occurs, it appears on the first level. The second should have no problem drying as long as you add it when the first is completely dry.
Aside from mahogany, exotic woods (a term often used to refer to wood from forest) usually have a very greasy resin. You can feel how slippery it is by touching the deck.
However, polyurethane contains a mineral alcohol solvent that can dissolve the resin. So when you apply the lacquer to the wooden board, the substances mix and prevent the last layer from drying out.
The final solution for this type of wood is to wipe off the oil on the surface with naphtha, acetone, or lacquer thinner before applying the polyurethane. Or you can use shellac to seal the resin in the wood. The substance also ensures that the surface does not bleed oil out later.
If you make a mistake: apply the coating without removing or handling the oil and try using the heat of a lamp or fryer to speed up the drying process. The effect is modest but worth trying. Otherwise, you’ll have to remove the last layer and apply a new one.
How to Remove Sticky Polyurethane?
First, use an old brush or roller to apply a layer of paint stripper to the area. Ensure that all corners are covered with the substance. Let it soak into the paint for 10 minutes. If the surface is bubbly and wrinkled, it can be treated. Do not use a water-based stripper, as this will take much longer.
Then use a scraper to scrub the transparent hard protective film (varnish). You must use plastic if you do not want to scratch and destroy the surface. Polyurethane is easily removed when you move the tool along with the wooden board. Just keep moving in the same direction as the wood grain.
So after washing, use a solvent that is used after the paint stripper to wipe the polyurethane. You can use a paper towel to remove the substance and wipe off the remaining varnish. Unlike a stripper, this substance does not need to be soaked before it is removed. If necessary, repeat the process until the sticky coating is completely removed.
How long do You wait before applying Polyurethane?
After staining, you must wait long enough before applying the finishing coats. Otherwise, the surface will not be able to dry and may look like the skin of a lizard.
So how long would it take a wood stain to dry? The waiting time may be different. However, it depends on the brands and conditions of the weather.
Most stain brands require consumers to wait 12 to 24 hours before adding the polyurethane coating. However, for best results, allow the interval to last 24 to 48 hours, especially if environmental factors are not ideal.
In short, you have to wait more than 24 hours before applying the first layer of polyurethane. Each top layer must remain untouched for at least 6 hours before a new one is applied.
The temperature best suited for drying stain is about 75 degrees Fahrenheit. However, as long as it’s anywhere between 50-90 degrees Fahrenheit, the drying process would take place accordingly.
Colder temperatures and high humidity tend to slow down the rate of drying. Hence you can direct the fan wind towards the surface or open windows to increase ventilation and speed the rate of drying.
On the other hand time taken for brands with penetrating stain to dry should not be too long. Except, you have applied too thick a layer on the surface. If the stain remains sticky after 12 hours, then it may need to be removed. If you leave the varnish there, it won’t dry naturally.
To remove the excess stain, apply another layer, and leave it on for a few minutes. Then wipe the surface. The movement only leaves the penetrated stain. Now you can allow it to dry and apply the polyurethane. If all of the stains are removed after you wipe it, consider sanding the surface again.
Application Process For Polyurethane
The application of polyurethane is easy, but it takes a long time, as each layer must be completely dry before you can apply the next. Some products are designed to be brushed, while others are made to be wiped on.
The painted product requires two or three thick coats, each of which must dry overnight. On the other hand, a wipe-on product takes four or five coats, each of which takes only two or three hours to dry.
Also, varnishes that are brushed are usually a little more stable, while the wipe-on ones have a slightly softer appearance. Keep in mind that dust from your work area can damage the coating if it gets into your project.
Frequently Asked Questions
How do you fix messed up polyurethane?
Apply polyurethane with a paintbrush in the direction of the wood grain. Brush on a thin, uniform layer to the sanded area and let it dry for about 12 hours before examining the finish for uniformity. Lightly hand sand the area and apply polyurethane continuously in thin coats until the finish is even.
Can you sleep in the house after polyurethane?
We recommend at least two days of sock-only traffic for finished floors with oil polyurethane. The house is not habitable for at least two days after the work has been completed. It is better to stay outside for at least five days as inhaling the fumes/exhaust fumes is not advisable even if there are other rooms to sleep in.
Can I sand tacky polyurethane?
If it’s sticky, then don’t sand it, or you’ll just have things gummed up like crazy. High humidity and low temperatures destroy the curing process. Also, keep in mind that there is a difference between touch attempts and hardening. You should be able to sand easily and get a fine powder at 220 or more, without lumps.
What is the best temperature to apply polyurethane?
The ideal conditions are 70 degrees Fahrenheit and 50-70% humidity. Refinishing furniture in an area of space that is below or above the range of 65-75 degrees Fahrenheit can cause problems, and the area below 55 degrees Fahrenheit is frigid.
Finally, it’s not rocket science to finish your wooden floors with polyurethane. However, it is a challenging job. A combination of skills and knowledge is required to apply the product.
Just like it is with any other home improvement project, proper selection and preparation will affect the results. Therefore you should take the time to practice your technique on scrap wood. One important thing you shouldn’t forget is to let your floors dry before sanding or walking on them.