Polyurethane sealer

Polyurethane Sealer: The Ultimate Guide

Spread the love

Making sure that your home is well protected from the elements is a vital consideration. The elements are not always kind to wood, and with a clear finish of polyurethane, you can solve that problem. But what is polyurethane, and why is it so effective at doing this job.

You will find as you begin to try to decide which polyurethane finish to go with that more and more questions arise. That is why, in this guide, we are going to breakdown and take an in-depth look at everything you need to know about polyurethane to make the right decision for your home or furniture needs.

What is Polyurethane? And How Is Polyurethane Made?

The first thing to understand is what it is. Polyurethane is a durable varnish that is constructed so that resin molecules in microscopic chains coagulate together as the application dries.

The end result of this is a coating that helps build water resistance, as well as resistance to abrasion and impacts that have been known to trouble traditional varnishes. There are many varieties, which we will discuss in the next section.

But before we get into that, let’s talk about how this amazing varnish is made. Polyurethane is created when polyol reacts with a diisocyanate while being mixed with a catalyst and additives. That wide range of these compounds means that polyurethane can be made into many materials.

Though we are focusing on varnish, it can also be made into foams, coatings, sealants, adhesives, and elastomers. And, our in-depth guide on t Polycrylic vs Polyurethane will help you decide which is the right one for your project. 

Types of Polyurethane

Just like with the materials that can be made from polyurethane, there are also multiple types of polyurethane varnishes. This market opened up because of restrictions on emissions, and here are the different types you have to choose from:

Oil Based

This polyurethane turns amber, which is a great way to warm up woods. This varnish forms a hard and durable layer with minimal coats. Unfortunately, this polyurethane doesn’t meet certain standards in some states, so it is not able to be purchased. This varnish can be cleaned with mineral spirits.


This varnish has a milky consistency until it dries, and then it is clear. It is a great choice if you want to keep the wood the natural color. Because it is watery, you will need more finishes, but it dries super quick in comparison to the other types of polyurethane. This type of varnish still needs ventilated areas while drying. It is easier to clean up as all it takes is some water and soap.

Water-Based with Oil Modification

This is a nice mixture of the other two options. It looks like a water-based polyurethane but dries like an oil-based varnish. That means you can bank on a tough amber layer of coverage on the wood surface you use it on. This varnish dries quick and works with all wood types. It also cleans up with simply water.

Polyurethane Guide

Gloss Levels – What Are They? And How to Choose One?

You will want to understand the different gloss levels as well before you choose which polyurethane varnish you go with. The finishes level of gloss will have effects on the amount of visibility of damages and scratches as well as the dust and dirt.

Here are the levels of gloss you have to choose from:


Matte is, of course, the least shiny of the finishes available when using polyurethane varnishes. This look will leave your wood with a protective layer but a dull, flat appearance that may be great for furniture and floors in more simple homes.


This is maybe one of the most popular choices for homes as it leaves a little shine that doesn’t overpower the rest of the house.


Semi-gloss gives a touch more shine than the satin level gloss but still doesn’t overdo it. This option is great for kitchens and areas where you will see significant traffic as it will allow your floor to have extra protection.


This is really only good for auditorium floors that need an extra shine. These floors with this level of gloss will need a lot of cleaning and maintenance to maintain the appearance you want.

What is the Best Polyurethane? Oil Vs. Water

The best way to determine which polyurethane varnish you should go with, you really need to break it down per the attribute. So, we thought we would help you out and do that for you. Here are the main factors to consider when choosing between oil and water:


If you are looking for the natural color of your wood to be shown off, then water-based is the way to go. If you want to add a slight amber hue to your wood, which could liven up a dull wood, then an oil-based polyurethane is the right choice. Though you do need to know that over time, it will darken, and this could affect the authenticity of the color of the wood.


Water-based varnish dries quicker, which means you will be able to lay down multiple layers in one day. With oil-based, it may take you a few days to get your layers laid down as it needs up to 24 hours to dry and cure. In fact, you will not even be able to walk on the floor for that entire day after you applied the oil-based varnish.


If you are working in an area that doesn’t have excellent ventilation, then you will want to go with a water-based varnish. They tend to have little to no smell, and it is very safe for people and pets to be in the home or area where you use the polyurethane varnish.

Whereas if you go with an oil-based solution, you will need to have specialized gear like a respirator and a well-ventilated room as it has a very strong chemical scent.

Thickness & Hardness

Oil-based polyurethane is a thicker solution, but it is also a softer compound. With a water-based option, you are dealing with acrylic, which ends up being a thinner and harder coating. Oil-based tends to be less durable and gather scratches and dents quickly. You will want to judge the choice off of the traffic type and amount when considering this category.


You may think that water-based is less expensive, but you will be thinking wrong. This product actually runs at a higher price than the oil-based option. Sometimes by double the amount to be honest. So, if you are dealing with large square footage, you may want to go with the oil option to save some money.


Some people have said that water-based varnishes leave a rougher feel. That would mean that with oil-based, you will be dealing with a smoother finish. Though if done properly, you should have just as smooth a result with either.


The durability of the varnish, no matter what type you choose, if done properly, will herald the same level of durability. Though many may say that water-based polyurethane is not as strong as the oil option, the truth is with the right product and extra layers; you can achieve the same level of durability.

Polyurethane FAQs

Now that we have taken a good look at some of the most important aspects regarding polyurethane varnishes, we are free to take a more in-depth look at some of the commonly asked questions online. Hopefully, the questions below will help you feel better equipped with the knowledge you need about polyurethane.

What is polyurethane used for?

Though, as we said, we focused on the varnish application of polyurethane, there are many other materials and applications that this product is used for. In fact, a majority of the application of this compound is in the form of foam. 

Though you can also find polyurethane in:

  • Elastomers in footwear
  • Hard plastics used in bezel and structural parts of electronic instruments
  • Plastics used in straps and bands
  • Injection-molded components for multiple markets

What kind of brush for polyurethane?

There are a lot of options on the market, and the best way to decide which brush you should buy to use with polyurethane is to understand the aspects of the product that needs to be considered. These are the factors that when combined, can create the perfect brush for you varnishing needs:


There are two options for bristles that you can choose from. You will have to choose from natural and synthetic bristles. Natural bristles usually are crafted of animal hair and work better with oil-based polyurethane. With the synthetic bristles, you will get a great option for rough-surfaced projects or if you are using a water-based option.

Width & style

This choice is made by the size and kind of project you will be working on. If you are looking to complete a big project, then you will want to go with a wider choice. The opposite is true if you are looking at a small project. Then you need to consider if you are going angled or flat. Most projects will work well with either, and so it really is a preferential choice at that point.


You will want to pay attention to the handle as it does play an important part in the process. If you go with a short, dense handle, this will be best for smaller projects. A larger, well crafted and contoured handle will offer a firmer grip, which will be handy when dealing with a larger project.


You will want to make sure, before you spend your hard-earned money, that the metal strip that keeps the bristles in place are sturdy. To do this, you will want to pull on the bristles a little and look for movement or shedding of the bristles.


Though you may want to skimp to save some money, you will definitely want to make sure that you are grabbing the best quality brush you can possibly grab. By spending a little extra up front, you will ensure durability and a better result on the project.

How to Fix Polyurethane

No matter what type of polyurethane you use, it is susceptible to scratches, which is one of the biggest issues you will face. There are many methods to fix this problem, but most will follow these steps:

You will need to decide what type of scratch you are dealing with. Is it deep or shallow? The type of scratch will determine the method of dealing with it. Though all of the options will start with the following steps.

You will want to clean the surface thoroughly. There can be no dirt or dust present on the surface.
If you are dealing with a shallow scratch, then all you have to do is apply a bit of wax then buff it until it is flush with the floor. Then let it dry and repeat the buffing.

If the scratch is deep, you will want to sand the area down with fine sandpaper. Make sure to move with the grain of the wood and use a light touch. Then clean the area again and let it dry completely before you move to the next step.

Once you have the wood fixed, you should add a stain to help hide the divot. Then you will add a new layer of the finish used initially.

How long does polyurethane need to dry?

Though the time allotment for your varnish to dry is dependent on a lot of other factors, the basic estimate of time for each type goes a little something like this:


  • 24 hours until it is safe to walk on the floor
  • 24-48 hours with socks, absolutely no shoes or bare feet. Try to keep pets off it as well.
  • After 48 hours you can walk the floor with shoes.
  • 4 days and you should be able to move the furniture back to its location.
  • 1-2 weeks would be perfect before you let any dogs or other housed pets walk on it without pet socks.
  • A full 30 days until you can say the floor is completely cured. Once this is done, you can replace any rugs.


  • 4-6 hrs. until you can walk on floors
  • 6-24 for walking with socks but still no shoes or bare feet. Also, keep pets off of the floor.
  • 1 day and then you can walk the floor with shoes.
  • 1-week until pets with socks can walk the floor.
  • A full 30 days until you can say the floor is completely cured. Once this is done, you can replace any rugs.

How to Apply Polyurethane

Though you may have different methods that you use, the basic structure will be the same. Here are the steps that you need to take:

  1. Prep by sanding the area. You will want to make sure that you have sanded the floor until it is smooth.
  2. Then you will want to seal the surface with polyurethane varnish and mineral spirits.
  3. Then you will want to apply a watered-down polyurethane coat.
  4. Then you will want to look for imperfections by shaving off them to make a smooth surface.
  5. Now it is time for the final coat.

How to Clean Polyurethane Off a Brush

Just as important as the actual application is the cleanup process. So that includes the steps you need to take to clean the polyurethane from your work brushes. Here is how you do that:

  1. You will need to gather together the equipment that you will need for the process. You will need paint thinner, a bowl, and a towel.
  2. Now you will want to fill the bowl up with paint thinner until it is about halfway full. This will only be used to dunk the bristles in, not the whole brush.
  3. Next, you will dip the brush into the bowl until the bristles are thoroughly saturated with paint thinner.
  4. If you need to add more paint thinner than do that here.
  5. Leave the brush in the bowl with the bristle fully covered for 15 to 20 minutes. This will allow the thinner to work its way into the brush.
  6. Next, you will remove the brush from the bowl and begin to rinse it in lukewarm water. It is important that you do not use cold water, as this may cause the compound to harden. You will also want to stay away from hot water as well as this can cause the adhesive holding the bristle in place to loosen.
  7. Now that the brush is clean of the substance, you will want to pat dry the brush with the towel.

What polyurethane is best for wood floors?

Either type of polyurethane would be suitable for any wood floors. It is more about what you are looking for rather than the materials it will be used on.

How to Get Polyurethane Off Skin

Typically, you will be using gloves when using polyurethane, but there may be the odd occasion that you may find polyurethane on your sin. If this happens, you will want to make sure that you act quickly to remove the compound for your skin. Here is how you do just that:

  1. You will want to use mineral spirits to rinse your hands. These can be bought at any hardware or art store and should be kept to clean the finish anyway. So, don’t worry, you will get use from it.
  2. Once you have rinsed your hands with the solution, you will want to rub the affected skin area with your hands vigorously.
  3. The next step is to wash off the mineral spirits.
  4. The next part of the process will be you taking a pumice stone and scrubbing the area for several minutes. You should begin to feel the compound removing itself from your skin. A pumice stone is easily found at any supermarket.
  5. If you still have some polyurethane present on your skin, you will want to repeat the process. Do so until the substance is fully removed from your skin.

How to Remove Polyurethane from Wood

There will be many occasions where you will want to strip the varnish from your wood floor or furniture. Here is how you will do that:

  • Gather together the tools you will need. This will be found on the varnish you previously used. Then you need to get all your protective gear on.
  • The next step is to apply your chosen stripper to your brush. The stripper needs to be thick but not thick enough that it will dry out in the time allotted. Typically, this is 10 minutes. You will want to work in small areas.
  • Now it is time to scrape the area of application with a putty knife or scraper. Clean the area as well then dry to decrease the wetness.
  • Then continue the process in the next area that is adjacent to the previous area.
  • Once you are done, you will want to sand the wood with fine-grained sandpaper. This will get rid of any raised areas left from the previous varnish application.
  • Then you will want to wipe down the area again to remove excess sawdust created by sanding.
  • Now you are free to begin the new application of your varnish or whatever treatment you are looking to do.

With all these questions answered, you are ready to get going on that project you have been holding off on. You have the ability to choose the right equipment, apply the compound, and clean up after. All your bases are covered so that no matter how big or small the project you are undertaking, you will have the answer for whatever comes up.

Final Thoughts

Understanding the ins and outs of polyurethane varnishes will allow you to complete your project with the best possible results. There is a lot to take in, and we hope that with all this information and knowledge that we have laid out above, you feel better able to make those critical decisions with the confidence of knowing that you will have no regrets. 

Now you have all the information you need about polyurethane thanks to this polyurethane guide. We hope all of your projects will be successful!

Leave a Comment

Your email address will not be published. Required fields are marked *

Data protection
, Owner: (Registered business address: Germany), processes personal data only to the extent strictly necessary for the operation of this website. All details in the privacy policy.
Data protection
, Owner: (Registered business address: Germany), processes personal data only to the extent strictly necessary for the operation of this website. All details in the privacy policy.