Polyurethane is the best finish for wood. Most woodworks are not complete without a polyurethane coating. Polyurethane varnish or coating consists of polyurethane resins that are dissolved and carried by a liquid solvent. It typically creates a type of plastic in the liquid state.
On the other hand, cleaning polyurethane stains caused by grease and grime after applying it on the wood can be challenging. Therefore we have prepared knowledge on how to clean polyurethane. Click; How to clean polyurethane for clear guides.
Varieties of polyurethane.
It is necessary to consider the types of polyurethane as you will be required to comprehend the product you are dealing with before looking at the drying times.
Water and oil are considered to make the liquid base of polyurethane. Both of them produce very different products with unique polyurethane dry times.
- Water-based polyurethane is safer and less harmful. Polyurethane contains lesser amounts of VOCs.They do not produce strong odors and are safer and easier to work with.
- Water evaporates fast, therefore, meaning that this type of polyurethane dries faster.
- Also, water-based finishes create a thinner coating hence making them dry faster.
Disadvantages of Water-Based Polyurethane
- You will be required to apply more coatings because a water-based polyurethane finish doesn’t last.
This thickness, combined with the oil composition, makes this polyurethane take more time to dry. However, you will eventually get a more substantial and long-lasting finish.
Disadvantages of Oil-based polyurethane
- Oil-based polyurethane can have high levels of VOCs, making them reasonably harmful due to the chemicals.
- They also produce a pungent smell.
Difference Between Oil and water-based polyurethane
The main difference between oil and water-based polyurethane is its clarity. Both of them become clear but oil-based ones yellow or darken over time. Water-based ones, on the other hand, generally maintain a better level of clearness with time.
Types of Sheen.
Second, consider the type of sheen the product has. Polyurethane coatings have three types of sheen.
- Satin- this type of finish is not as shiny as the others. It has an almost matte look with very little subtle shine. This type takes the fastest time to dry.
- Semi-gloss- this is the middle ground between glossy and flat. The semi-gloss ones give a finish that has some shine but is not as shiny as the high-gloss ones. It is an available choice due to its versatility and durability. It dries faster than high-gloss ones but slightly slower than satin products.
- High-gloss– these products give a gleaming and good-looking finish. It is durable and offers excellent flexibility.
Factors to consider when choosing the type of polyurethane
Indoors and outdoor wood surfaces can use the high-gloss product. However, this type takes a slightly longer time to dry.
Also, before looking at the drying time of polyurethane, it is best to look at its cure time. The cure time of polyurethane is affected by the temperature, humidity as well as surface.
Water-based polyurethane takes around 8 hours before adding another layer, 24 hours to dry for touching, two days to place items on the surface, and 20 days to be completely cured.
On the other hand, oil-based polyurethane takes 24 hours for you to be allowed to add another layer, 48 hours to dry for touch, four days for placing items on the surface, and 30 days to get fully cured.
In addition, please wait for a month for you to place things like rubber mats on the surface to prevent them from leaving visible marks on the floor.
Difference Between Curing Time and Drying Time
Dried polyurethane is not cured polyurethane.
Drying is when the external coating of polyurethane hardens. It means that the polyurethane neither in a liquid state nor wet.
This state, however, does not dictate that the surface is ready for use. Too much pressure and wrinkles can damage this finish. Therefore, do not put the surface under heavy use when it is just dry.
Curing, on the other hand, is when the polyurethane has completely hardened. Here, the polyurethane has been highly exposed to oxygen and has undertaken a complete chemical reaction with the oxygen.
Cured polyurethane, therefore, is the final, hardened finish. This final condition then allows you to exert hard use on the surface. Curing is a long process that could take from a day to almost a month.
The period needed for both water-based and oil-based polyurethane to dry.
- appears dry six hours after being applied. This duration means that;
- it should not feel wet when touched, and no pets or shoes should touch it. After that, it is okay to sand and cleans well after sanding.
- Next, add another layer of varnish. After 24 hours, it will be okay to wear shoes. Two days later, it will be okay to replace the furniture. Do not cover the surface for a minimum of 2 weeks. The surface cures entirely after 30 days.
- surface should appear dry or not feel wet when touched after 24 hours.
- Please do not step on it, and no pets.
- After that, sanding is a necessary and thorough cleaning.
- It is now okay to add another layer of coating.
- 48 hours after application, it is now okay to wear shoes.
- 4 days after application, it is acceptable to replace the furniture. Lastly, leave the surface uncovered for at least two weeks without placing any throw rugs or mats. The surface cures fully after 30 days.
How to speed up the drying time for polyurethane.
If you want polyurethane to dry faster, follow the following essential guides.
- Use heat in cold weather conditions or cold areas. Apply a heat source if the cold weather delays the drying period of polyurethane, for example, using a hairdryer or wall heater. Apply a gentle amount of heat because too much heat will damage the finish.
- Use a paint roller to smoothen polyurethane that becomes too thick. Roll over the applied finish to give even and thin layers. Rolling also makes the coating to be completely smooth.
- Always check on the weather conditions from the weather report before deciding to apply polyurethane outdoors. If it will rain or there is any humidity coming, the change the day of doing so.
- When in humid conditions, consider applying oil-based polyurethane, unlike water-based one, because of its sensitivity to humidity. Oil drys faster in humidity and gives you a durable outcome.
- Always ensure that the surface you are going to apply polyurethane on is appropriately prepared. A clean, clear, and sanded wooden surface will make the polyurethane adhere better and dry quickly.
Lastly, to achieve the best finish, you will be required to apply polyurethane in layers. You must know when to apply the next layer and when the underlying coat is dry enough.
To apply the next layer, ensure that the first layer is not wet anymore. Gently touch the surface to determine when to apply the next layer. The same applies to the third layer.
After the last layer, leave the polyurethane to cure completely before use. Depending on the type of product, each layer could take about 1 to 8 hours to dry.
Factors that affect drying and curing time of polyurethane.
Type of polyurethane.
It is crucial to note that there are many other subcategories in every water-based and oil-based polyurethane category.
Also, some manufacturers might include drying agents. Some add oil and probably other solvents. You can also get stains to add colour and so on.
Therefore every component could affect the dry and cure time slightly, or it could force you to adjust your entire approach.
In conclusion, water-based polyurethane dries faster than oil-based polyurethane.
Type of wood.
Some woods emit chemicals that prevent polyurethane’s crosslinking process, making them not dry entirely. For example, some aromatic cedars and Rosewoods.
Temperature and Humidity.
The period mentioned above is 70° F/ 21°C a day and 70% humidity.
If the temperature rises and becomes dryer, the drying time fastens than earlier mentioned.
From another perspective, a cooler temperature on a wet day might extend the drying period by as much as half a day.
The surface you begin with.
Raw sanded surfaces absorb the first layer, thus decreasing the dry time. This fall-off is because the first layer wets and seals the wood.
Every next varnish consists of applying one layer on top of an existing layer of polyurethane, and it will take more time to dry.
To conclude, the safety of using polyurethane depends on the specific type and brand. Before using any chemical, always read the instructions first.
Oil-based polyurethane is more harmful. Therefore, if you suffer from any respiratory diseases, consider that polyurethane generates fumes that irritate people with these problems. Oil-based polyurethane is also flammable when wet during the drying period. If exposed to any ignition source, they could catch fire. Therefore, avoid smoking or any other activity that would generate sparks and have a fire extinguisher.
In addition, stay away from prolonged exposure while working with polyurethane. Ensure that the area is well ventilated and follow the instructions.