Polyurethanes are some of the most commonly found materials in human-made objects. Their durable, malleable and anti-weathering properties leave them with no shortage of possible applications. From making your mattresses more elastic to insulating your homes and refrigerators, it’s hard to imagine how you could go wrong with polyurethane.
Wood workers are especially familiar with this magic material as it is used as both a sealant and finisher for wooden floors, cabinets and furniture, but also as a binding agent between different materials. For small wooden projects, most wood workers use a brush to apply their coats of polyurethane. However, for a larger wood working project, like a wooden floor, it is possible to achieve great results using a roller instead.
So if you’re looking to finish or refinish a large wooden panel or a wooden floor, you’ve come to the right place. In this blog we will guide you through the step by step process of using a roller to apply polyurethane. The Guide will lay out the process of using Polyurethane to finish a wooden floor, as that will provide an overview of all the essentials of using a roller to apply Polyurethane.
- Paint Roller
- Lamb’s Wool Applicator for roller
- Mixing Pan
- Mineral Spirits
- Oil-Based Polyurethane
- Cotton Cloth
- Vacuum Cleaner
- Painter’s Tape
Oil-Based V.S Water-Based Polyurethanes
All Polyurethane that is manufactured specifically for finishing and sealing wooden panels is readily available at any hardware store. These kinds of polyurethane come in metal cans and have a liquid like consistency to them.
The very first fork in the road that you are likely to encounter when taking on any project involving polyurethane is likely to be: should I use oil or water based polyurethane? The answer is not so simple and depends on the kind of project you are working on as both kinds of polyurethane provide great protection. However, there are some key differences that must be understood.
The first thing to note is that oil-based polyurethane are less expensive than water –based. So right off the bat, if you’re working under a budget this might be the right choice.
However, there are other factors that you might want to be aware of. Oil-based polyurethane leaves an amber glow and requires fewer coats to get the final finish. Further, oil-based polyurethane contains 40 to 50% more solids making it more protective and requiring less maintenance over time.
These benefits do come with a cost though. The higher durability of oil-based polyurethane means that there is a minimum 5-hour wait in between each coat application. This will mean that during your project you’re likely to put a whole room out of commission for a day or two.
This kind of material is also very hard to clean and tends to ruin brushes and stain clothes. Lastly, oil-based polyurethane tends to give off a pungent odor for a few days after application which might be a deal breaker in itself.
On the other hand, water-based polyurethane provides a clear, non-glowing finish and gives off much less odor. Moreover, this type of coat dries in about half the time as its competitor. This means that you might be able to get all your coats finished in a single day and not put the room out of use a night.
Water-based polyurethane works really well on certain types of woods, like maple, which have an inherently more natural look to them. The water-based material allows the wood to be the star of the show. However, some woods, like oak cry out for that shiny amber coat left by oil-based polyurethane.
Again, the choice of water-based polyurethane comes with a few costs. Firstly, this material is normally about twice as expensive as oil-based. Moreover, these polyurethane are less durable and protective, containing about 10% less solids than their oil-based counterparts. This means that you have to apply more coats to achieve your final finish.
These types of polyurethanes have a tendency to go clear soon after application, making it necessary to mark where you have applied the material. Lastly, the lack of durability of water-based also means you might have to apply a refinish every two years or so.
Mixing Polyurethane with Mineral Spirits
Since the most popular choice for wood workers when finishing a floor seems to be Oil-based polyurethane, we will stick to that material throughout our guide. As mentioned, these polyurethanes contain more solids and are hence thicker and more durable.
However, this too comes at a price. The thicker the polyurethane that is used the more likelihood there is to get trapped air in between coats. The thicker material acts as a protective layer around trapped air, not allowing it to escape.
A simple hack solution for this problem (other than choosing water-based polyurethanes) is to mix your oil-based polyurethane with Mineral Spirits. This is an organic solvent made of 100% petroleum distillates. It is used for a wide variety of applications, but is most commonly used for thinning oil-based paints.
A good ratio to follow for making this mixture is to use 3 parts oil-based polyurethane and 1 part Mineral Spirits. This will thin out your oil-based material, decreasing dry time, but more importantly, reducing the likelihood of trapping air in between your coats. This hack is used by many wood workers and painters, and allows you to achieve a middle-ground between oil-based and water-based polyurethane.
Why Use a Roller?
Coming closer to the main objective of this guide, which is to learn how to successfully apply a polyurethane finish using a roller, you might be asking this question. Why use a roller at all? Why not just a regular brush?
The most obvious advantage that using a roller provides is the exact same reason why painters use a roller when applying coats to walls or large panels. Using a roller eliminates brush strokes and makes for the possibility of a smooth and even coat of polyurethane. Using a roller also prevents one from over applying the material to the surface. This factor is very important for applying polyurethane as an uneven coat can cause cracks in the wood in the long-run.
Second, due to the way they are made, it is very easy for air to become trapped within the bristles of a brush. This can cause many problems when applying our coats as the air can interfere with the evenness of the coat. Moreover, brushes often shed their fine bristles while in use, especially when using thick materials. These bristles are very hard to see when they fall onto the floor and if they get stuck in between coats, they will stay there and ruin the evenness.
Using a roller helps to avoid all of these problems and of course saves time as you are able to apply coats to larger areas in shorter spans of time.
What Kind of Roller Should I Use?
While it is possible to get the job done adequately with pretty much any type of roller, using specific kinds can help you avoid cracks and discrepancies in your polyurethane coat. Since oil-based polyurethane is quite think, it is quite hard to prevent dust and lint from mixing with the finish. This problem is compounded with the use of normal paint rollers which are not super absorbent and might leave dust and lint behind in their tracks.
A very good alternative is lamb’s wool applicator. As the name suggests this is a material made of lamb’s wool fibers, which can be wrapped around the regular roller spool. This material is highly absorbent, which means you don’t have to repeatedly dip it in the polyurethane to get good results. Importantly, this attribute also lowers the possibility of dust and lint being left behind by the roller.
Before we can get to our polyurethane application we need to make sure we prepare both the room we are working in, as well as the materials we are working with.
Cleaning the Floor
Before you get started, it is essential to get rid of all the dust on your wooden floor that has already collected. Start by using a vacuum cleaner to get rid of all the large debris like lint, dust balls and hair.
The next thing is to use a wet rag to mop the floor. This will make sure to catch all the minute dust particles that have collected on your floor. Make sure to do this step slowly and thoroughly. Moreover, make sure you have many rags on hand as you don’t want to keep using the same one once you’ve already used it to clean up dust.
Finally, once this is done leave the floor to dry completely. It is best to let it dry naturally, rather than exposing the room to ventilation from outdoors. This may just cause fresh dust and small debris to wash up on your clean floor once again, making the entire process futile.
Cleaning the Roller
Dust tends to accumulate on the material used for rolling as well. If you have ordered a new lamb’s wool applicator for your roller, this is no exception. Dust from the manufacturing and packaging process may have accumulated onto the material. As mentioned, any source of dust means bad news for your polyurethane coat.
Cleaning the woolen applicator is only a three-step process. The first step involves some painter’s tape, which is designed to have lowered stickiness so that painters can remove it from their canvas easily. Fold a piece of the tape into a loop with the sticky side on the outside. Now brush the sticky side of this tape across your lamb’s wool applicator. The material is sticky enough that it will catch dust laying on your applicator, but not so sticky that its starts taking apart the fibers that make up the material.
After this step pour some mineral spirits over the applicator and wash it in with your fingers. Please wear protective gloves during this stage!
Remember not to rub too abrasively as you might ruin the fibers of your roller’s material. Use gentle but thorough rubbing and make sure to get every inch of the material’s surface. After this you can leave the applicator out in the sun to dry. Do not use it until it has dried properly and completely.
Applying Polyurethane to the Wooden Floor
Image Text: Refinishing your wooden floor can have a lasting impact on your home
Alt Text: For glistening and healthy wooden floors use Polyurethane as a finisher
Image Description: A home set up with couches and a rug over well-finished wooden flooring
Before touching any of your materials make sure you are wearing protective gloves and a nose mask. The pungent odors from both the mineral spirits as well as the oil-based polyurethane can be quite harmful so make sure to take proper safety measures.
You also might want to wear an apron, or some old clothes that can afford to get dirty. While you should try to work as cleanly as possible, accidents do happen and it’s best to be prepared rather than sorry. Another pro-tip for applying finishes to floors is to protect your shoes using a plastic covering tied at your ankles.
Once you’ve got protective gear on, mix 1 part of your mineral spirits solution with 3 parts of your oil-based polyurethane. Make sure to pour and stir the two very slowly as any harsh motions will cause air to become trapped within the mixture itself.
Mentally mark out sections of your wooden floor each about 5 feet by 5 feet and choose which one you are going to start with first. This is an important step and trying to apply coats to the entire floor in a single go can easily cause mistakes.
Pro Tip: Make sure that the first 5 by 5 section you cover is the corner of the room farthest from the exit. This means that you should progressively apply coats to your sections in a manner that leaves the section nearest the door for last. This is important as you don’t want to have to walk over an already coated section just to apply a coat elsewhere. You want to coat the room in such a manner that you never have to step on a spot that is already coated with your polyurethane mixture.
Dip your roller into the polyurethane mixture, making sure to dampen the entire surface of the roller.
Place your roller in the very middle of one of your 5 by 5 sections and begin to apply the coat moving outward from this centre point. This is to ensure that you don’t get large blobs of polyurethane mixture in the sides or corners of your floor where you won’t be able to spread them out. Create a blob in the middle of the section and spread the mixture out in lines towards the sides and corner.
For this you will need a very light touch on the roller. Remember that you are not trying to work the polyurethane into the wood, as you might when working with paint. You are simply using the roller to lay the polyurethane mixture onto the surface of the wood in even coats.
Therefore, do not press down on your roller very hard and lightly lay the mixture onto the surface in vertical lines that move into one another. This will ensure that you apply a level coat and don’t miss any spots. Continue until there is no more polyurethane mixture left on the roller.
Repeat step three and move on to the next 5 by 5 section, making sure to leave the section closest to the door for last.
You will notice that the certain spots of your Polyurethane coat start to show white bubbles on the surface. This is completely normal and not a cause for alarm, as it is a part of the Polyurethane’s drying process. The majority of these bubbles should disappear once the coat is dry. And if a few bubbles still remain by that point, then you’ll know for sure that there was something wrong with the applicator or the method of application.
Allow the first complete coat adequate time to dry. You can find the approximate time it takes for your polyurethane product to dry by reading the manufacturer’s label on the can. Remember, however, that the addition of mineral spirits to our oil-based polyurethane tends to reduce the dry time.
Pay special attention to your drying coat, making sure not to disturb it while it is still wet and keeping the room well ventilated to allow the pungent smell a chance to escape.
Once the first coat has entirely dried, it is time to sand. Using sandpaper to roughen the surface of your Polyurethane coat will pop some of those nasty air bubbles that might still remain. This will also prepare it for the second coat.
Use a 280-grit sand paper or slightly higher and rub the entire surface of your polyurethane coat. Make sure not to rub too abrasively as you aren’t trying to flush down the surface, only roughen it up.
Next, dip a cotton cloth into the mineral spirits solution to dampen it and wring out the excess. Use this damp cloth to wipe down the surface to clean off any dust left over from the sanding.
To apply additional coats of Polyurethane repeat steps two to eight. Apply the coat to the 5 by 5 sections in the same order as you did before.
Coating the Edges
One of the biggest drawbacks of using a roller to apply a coat of anything is that it is terrible at reaching corners and the edges where the floor meets the wall. These edges can be coated using a brush made from animal hairs, like oxen hair brushes. Do not use paintbrushes when working with Polyurethane as its sticks to the paintbrush fibers.
This step needs to be done while the roller is being used to apply the coats across the floor. Alternatively it can be done right before, starting with the edges of the floor farthest from the door and working in a way that leads you outside the room.
However, note that this step cannot be done after the coat is already applied across the floor as that would mean stepping over the already applied Polyurethane in order to apply a coat on the edges. If you are working on the project alone, get these hard-to-reach areas first. If you have a partner to help you, coordinate accordingly and do them more-or-less at the same time.
No good wood working project can possibly be complete without clean up at the end. In this case, cleaning up can be a real pain as oil-based Polyurethane tends to dry up into a thick and durable layer over anything it comes into contact with.
To clean your paint roller, run hot water over it to remove any remaining Polyurethane and mineral spirits off it. For the pan that contained the Polyurethane mixture you can also use hot water, however, since the pan is likely made of plastic or a cheap metal, the substance will dry over it in large blobs. You get rid of these you can use a large flat-head screwdriver to wrench them off.
If it seems that you are unable to get some Polyurethane off your mixing pan, it might be best to dispose of the pan altogether as using it again in the future might causes problems for whatever project you will work on.
So there you have it! Through this complete step by step guide to applying Polyurethane using a roller, we hope that you can successfully apply a beautiful and lasting finish to your wooden flooring. Using chemicals and similar materials in DIY projects can be confusing, but by staying informed and practicing the steps, we are sure that you shouldn’t encounter any problems.