Whether you have an art project that features a wood frame or simply want to pour epoxy floor over your hardwood floors, you might be wondering whether the material even sticks to wood. Even though these are different types of epoxy, they have similarly strong adhesion.
Epoxy resins stick to wood in most cases, with the only exception being wood with a smooth finish being subjected to extra-thick epoxy resin. In such a case, the resin would not get into pores where it can solidify and anchor. In all other cases, it will have a firm hold on wood.
In this article, you will discover what factors affect epoxy resin’s adhesion to wood. Starting with the roughness of the wood and ending with the pouring period, this post tells you everything you need to know to pour a long-lasting epoxy layer over a wooden surface.
The Roughness of the Wooden Surface
Epoxy resin starts off as a viscous liquid and turns into a supercooled liquid. In case you’re not familiar with supercooled liquids, these are solids that result from a very thick liquid curing at room temperature.
Glass is an example of a commonly used supercooled liquid. Does Glass stick to wood? No, because it is cured in isolation. Similarly, the epoxy resin would not stick to a wooden surface if it were pre-cured.
Supercooled liquids latch onto another surface when they’re poured in a liquid state on the said surface. The liquid seeps into the pored of the surface and solidifies, which creates roots that hold together the supercooled liquid and the surface it cures on. For maximum hold, the surface must be rough. The more porous the wood on which you pour an epoxy resin, the better hold epoxy will have on it.
To facilitate this phenomenon, the wood surface undergoes surface preparation. In this, the surface is cleaned and then roughed with sanding paper of appropriate grit. I’ve discussed selecting the right sandpaper in my post on pouring epoxy on wood.
Whether the Surface is Polished or Sealed
Resulting from the phenomenon of seeped liquid solidifying to form surface roots is the second factor that dictates the degree of hold epoxy has over a piece of wood. Just like sanding makes the wood more porous, polish and sealant can make the wood too smooth for the epoxy to latch on. This would fall under the surface roughness if it weren’t possible to polish wood and still have it ready for an epoxy pour.
It is a myth that epoxy won’t stick to polished wood or sealed surfaces. The true element is that if a sealant or polish is thick enough to fill the pores on a wooden surface, epoxy will form a layer over the wood instead of seeping into it and latching on. With that in mind, one can deduce that how thin a polish is dictates how well the epoxy sticks to wood. Obviously, the surface is most conducive to the resin when there is no polish clogging up its pores.
However, if a sufficiently thin polish is applied to wood, it can still have room for the epoxy resin to seep in and grab hold. The case is a little less practical with a sealant since the latter’s main function is to block pores. Diluting a sealant to the point that it is too thin to block surface pores would defeat the purpose of a sealant.
The Viscosity of the Resin
Polish thickness isn’t the only type of viscosity that matters. In fact, the resin’s own thickness matters more. Even if a wood surface is completely clogged to a smooth finish, you can always send it to make it ready for pouring epoxy.
Sometimes, you might need power sanding, but still, you’ll be able to make epoxy stick to wood. However, if the epoxy resin itself is too thick, you’ll have tough luck pouring a stable layer and getting it to stick.
Always get a two-part epoxy resin system and rest it on a patch of the same wood surface. Make sure the test surface is prepared in the same way as the main surface and features the same wood, polish, and sanding. If the epoxy you pour doesn’t cure to touch with a hint of stability, you must add thinner to facilitate flow and deeper reach in smaller pores.
Period Since Pouring
The keyword in the previous section is “cure to touch.” Epoxy resin cures in two main milestones. The first is where the surface becomes dry to touch. The resin hasn’t fully cured at this point but can be touched without transfer.
Usually, you’re supposed to supervise the surface until it is dry to touch, which usually takes an hour. The thinner the resin, the longer it takes. When enough time passes, epoxy can stick to almost any surface, albeit with a different degree of adhesion. But how well the resin sticks to wood depends on when you’re checking.
If 24 hours have passed since you poured epoxy resin on a wooden surface, the resin should stick to the wood. In case the time since pouring is less than an hour, the resin will not stick. Do not touch the epoxy resin, and don’t second-guess your pour during the first two hours. If the resin doesn’t cure to a stable degree after two hours, it may be too thin, or the pour itself must be too thick. This can be a little confusing.
For epoxy resin to stick to wood after one hour of pouring, the resin must be thin enough that it can flow and spread all over the surface. It should not be any thinner than it has the be. This refers to the dilution of the epoxy with a thinning chemical.
The thickness refers to the layer of epoxy poured atop the wood. When this layer is too thick, it becomes unstable. Pouring thinner layers in succession after curing one at a time is the practical way to get a thick body of epoxy to stick to wood.
The epoxy resin sticks to wood in most cases. The conditions under which epoxy won’t stick to wood are so rare that even unintentional pours have excellent adhesion. In fact, you have to actively try to pour resin in a way that doesn’t stick to wood. That said, you should still prepare a wooden surface to be optimally conducive to epoxy.