Epoxy and polyurethane both are very essential items to make your woodwork project weather-resistant and shining. Both have different characteristics and applying methods. So, let’s find out what is the best way to use them together.
Can you put epoxy over polyurethane?
Applying epoxy over polyurethane is possible. But it should not be done intentionally as it has no benefit. If one has previously polyurethane coated wood, he can apply an epoxy layer over it without any problem. However, to apply epoxy over polyurethane, the poly must not be water-based.
Epoxy and polyurethane can bond nicely with each other. Epoxy is harder and polyurethane is flexible and weather-proof.
Let’s break it down. To understand why epoxy over polyurethane is not a good idea, we will have to understand the nature of each material.
Epoxy is durable and rock-solid when cured. It can take heavy loads and is flexible enough to make different shapes with mold. Those things make it a decent base building material. But it has some problems too.
The UV ray of the sun reacts with its molecules and makes it unappealing and weak. It also does not resist high moisture and some chemicals.
As epoxy is hard and non-flexible, it is prone to scratches. Those characteristics make it a bad choice for applying at the outermost part of a woodwork project.
Let’s keep it here. We will discuss polyurethane in the next section where we will explain the advantages of polyurethane over epoxy layers.
So, when should you apply epoxy over polyurethane? Can you put tabletop epoxy over polyurethane? Or clear epoxy resin over a polyurethane surfboard?
When you have something that has a polyurethane layer previously, and you want to coat it with epoxy, you can go on.
If you applied polyurethane over a table before. Then if you change your mind and want to apply both epoxy and poly layers to make it more durable, you can apply epoxy over it. But the table must be sanded properly before applying.
Epoxy resin can be applied over a polyurethane surfboard, but another poly layer must be applied to make it tough and weather-proof.
It is also possible to use 2 part epoxy over the polyurethane layer. That means you can make as many parts as you want over poly if you have mold.
Check out if those combinations are possible.
Epoxy over an oil-based polyurethane:
Epoxy over oil-based poly is possible, but the oil-based poly must be cured.
Epoxy over water-based polyurethane:
Epoxy must not be used over water-based poly. It is hard to apply and does not stick well.
Does epoxy adhere to polyurethane?
Epoxy perfectly adheres to polyurethane and polyurethane also sticks to epoxy nicely. But before applying epoxy or polyurethane, some procedures must be followed for perfection.
First, the epoxy (or poly) layer should be sanded with 100x sandpaper to make the surface smooth. The sanding process also helps the next layer to be stronger.
Before applying, the previous layer must be cured perfectly. Patience is key to getting perfectly done resin layers.
Also, before applying any resin or poly, make sure to clean any kind of dust and substrate over the wood surface.
How do you prepare polyurethane for epoxy?
For wood, oil-based polyurethane is best as it gives the wood a nice warm color and it is easy to use.
It does not require any fancy preparation method before using it anywhere. Follow the tips below to perfectly apply polyurethane.
The polyurethane liquid must be mixed before applying but shaking will create air bubbles inside. Air bubbles must not be there for a smooth finish.
Instead, mix the polyurethane with a stick properly. Do it nice and gently to avoid air bubbles. After mixing it for 3-4 min, it is ready to use.
Use a synthetic paintbrush to apply polyurethane. A foam brush can be also used for application.
Pull a long, straight line with your brush. Always follow the wood stain while applying the polyurethane.
After applying a layer, wait for one hour before applying another. At least 3 layers should be applied. After completing the layering, wait for 24 hours.
Sanding and polishing:
The polyurethane layer should be polished for best results. Polishing must be done after about 24-48 hours.
How to apply epoxy over polyurethane?
For applying epoxy over polyurethane, you will need a cleaning agent, sandpaper, and safety equipment. Here are the steps of applying epoxy over the polyurethane layer.
First, use sandpaper to make the surface smooth. 100x sandpapers are the best for sanding polyurethane layers.
Wash the surface:
Wash the surface with mild detergent to remove all the dirt and dust. Make sure to remove any kind of dirt or outside particles. After washing, wipe the surface with a clean napkin.
Dry the surface:
Let it dry for a few hours. Make sure the surface is dried completely. Now it is ready to apply epoxy.
Follow the same way as applying epoxy on wood. The Epoxy applying method is further described below.
Can you put polyurethane over epoxy?
Polyurethane should be applied over the epoxy layer for the best outcome. Those two make an amazing combination. Polyurethane is not so hardy as epoxy. While epoxy can’t resist so many things that polyurethane can resist easily. A few layers of poly protect epoxy from UV rays of the sun.
Epoxy can resist water and makes an object hardy. But it is not good to be used in the outermost layer of something. The polyurethane layer protects the epoxy layer from UV light, chemicals, and scratches. Here are some features of polyurethane.
Polyurethane can bear a high amount of load while being flexible. The flexibility helps to make the surface scratch-proof.
It can resist not only water but also oil and grease. It is an important feature as a coating of tables or floors.
Polyurethane is a good insulator of heat and electricity. It can resist mold and funguses when cured perfectly and does not get affected by harsh environmental conditions and degradation.
So, what else can you ask from the outer layer of a table or floor!
There are many reasons why you should use a polyurethane layer over epoxy resin. The polyurethane layer absorbs less moisture than the epoxy layer. Epoxy starts to degrade in direct sunlight.
The polyurethane layer protects it from UV rays. When epoxy and poly are used to coat something, it becomes durable and protected.
Check out if those combinations work or not.
Polyurethane over epoxy resin:
Polyurethane can be applied to epoxy resin and it is the most preferred way to use them.
Polyurethane over epoxy paint:
Polyurethane over epoxy paint is also applicable. It is a good way to make the paint long-lasting. But make sure to clean the surface before you start brushing.
Oil-based polyurethane over epoxy:
Oil-based polyurethane is best to use over epoxy layers. Before applying oil-based poly, the epoxy resin must be sanded and polished well.
Water-based polyurethane over epoxy:
Water-based polyurethane can be applicable over epoxy layers, but oil-based poly shows the best result.
Can you put polyurethane over sticky or tacky epoxy?
You can put polyurethane over sticky or tacky epoxy. But it is not advisable as it will be glomy as a final result. But if you can ensure that you clean and wash the surface thoroughly, then you can put the polyurethane coat over.
This way, you can easily make the top coat look smooth and finished as a shiny one.
How do you apply polyurethane to epoxy?
Before starting, prepare your place and collect all the safety equipment. Protective chemical-proof hand gloves, eye protectors, and respirators should be equipped before starting the work. Follow the steps to apply polyurethane over the epoxy layer.
First of all the wood should be nicely shaped and sanded. Old burnish or other coats must be removed. Use 100 and 220 grit sandpaper to make the surface smooth.
Prepare your epoxy by mixing it with resin and hardener. The ratio is 2:1 for most of the epoxy brands.
After mixing, apply the epoxy over wood. It should take 24 hours to dry but it needs to cure for another 7 days before applying polyurethane.
After opening the can, stair the poly with a clean stick. After mixing it well, use a synthetic brush or foam brush to apply polyurethane.
Use long and straight strikes to apply it. Do not overlap and follow the wood stain while applying.
After completing a layer, wait for 1-2 hours. Follow the instructions to know the exact time between layers. Then apply another layer of poly and wait another 1-2 hours. Keep applying like this.
You must apply 3 layers minimum while 4-5 layers are best. Finish the job by sanding and polishing after curing.
Polyurethane over epoxy is the most preferred way to coat something. Epoxy can also be used over poly layers but it does not have the benefits of the poly layers. The application process must be done with proper ventilation, lights, tools, and safety equipment.