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Primaloc Answers: Should You Sand Between Applying Coats of Epoxy?

Premium epoxy resin is remarkable. Tough like metal but clear like glass, while also resilient to many different types of corrosive chemicals, it's become a premium choice as a sealant for major furniture and fixture projects such as table tops, bar tops, and countertops.

Moreover, its aesthetic appeal and highly customizable appearance lends itself well to many forms of art and similar creative endeavors, showing up in homes as a decorative element, as well as for use in the creation of functional items such as trays, coasters, and tumblers.

As well, epoxy resin is also accessible, being easy to learn and straightforward in application. The process is time-sensitive but not too rigid.

Epoxy Is Applied in Layers, One at a Time

That said, epoxy in its simplicity does exhibit its own peculiarities. It starts off in a liquid form as two separate components. These components are measured and mixed together to instigate the curing process, which allows it to harden into its iconic form.

While in that liquid form, though, it's quite viscous. This viscosity varies by brand and variant but is a fundamental trait to epoxy as a sealant. As such, the application of epoxy must be done in layers with a maximum thickness/depth.

Most premium epoxies—especially bar top epoxies—are self-leveling, meaning they spread out naturally until they reach a point of equilibrium, settling at an inherent thickness level. This is considered the maximum recommended thickness for an epoxy layer, with additional layers being added on as needed to achieve particular project goals.

An epoxy finish with air bubbles suspended within.

Air Bubbles, the Reason for the Rule

The reason why epoxy is applied in layers is due to air bubble formation. In most cases, epoxy resin is applied to porous substrate. These materials have numerous pores, which are essentially tiny holes that tend to house pockets of air.

When a liquid sealant is applied to a porous material, the fluid permeates those pores, pushing out the air and allowing it to escape. Premium epoxy, however, is so viscous that it can prevent the air from fully escaping if the coating is too thick; the air instead becomes suspended within the epoxy finish, often appearing to be a blemish or imperfection.

To avoid this issue, epoxy is applied in multiple, subsequent layers. The first layer is often a seal coat of epoxy. This is a thin, manually brushed-on layer of epoxy resin that forces the air out. Notably, it's thinner, allowing the air to escape easily so that it doesn't become suspended in the finish.

A few hours after a seal coat begins curing, the epoxy flood coat is applied. While most projects—e.g., an epoxy table top—will only need one, a second flood coating can be performed after a partial curing of the previous.

It's when multiple coatings of epoxy are involved that we get to the question at the crux of this article, "Should you sand between applying coats of epoxy?"

A man holding an orbital sander about to begin sanding

Should You Sand Between Applying Coats of Epoxy?

In most cases, yes, you should sand between applying multiple coatings of epoxy, especially if you're applying multiple layers to add a clear topcoat over colored or textured epoxy or simply to build up thickness. Sanding ensures proper adhesion between layers and creates a smoother, more professional finish.

Here's When and How You Should Sand:

#1: Wait for the Epoxy to Partially Cure

Before sanding, the initial epoxy layer should be cured enough to be solid but not fully hardened, usually after 24 hours. If the epoxy is too soft, it will gum up the sandpaper; if it's too hard, sanding will be more challenging and less effective.

#2: Use an Appropriate Grit Sandpaper

Start with a medium-grit sandpaper (around 120-220 grit) to lightly scuff the surface. You're not trying to remove the epoxy layer; you just need to create a slightly textured surface that the next epoxy layer can mechanically bond to.

#3: Clean the Surface

After sanding, it's crucial to remove all dust and debris from the surface. Wipe it down with a tack cloth or a clean, damp rag to ensure no particles are left behind to interfere with the next coat.

#4: Apply the Next Coat

Once the surface is clean and dry, you can apply the next layer of epoxy. The mechanical bond created by the sanding will help the layers adhere more securely, reducing the risk of delamination.

If you're applying a final topcoat or if the subsequent layer is the last one, sanding can also help remove any imperfections or bumps from the previous layer, ensuring a smooth, high-quality finish. Always follow the manufacturer's instructions regarding the curing time and sanding recommendations for the best results.

A flood coat batch of epoxy resin being poured onto a wooden substrate surface.

Which Coats Should You Sand After?

Sanding isn't necessary after every type of coating. During a typical epoxy project, there are usually two different types of coating you'll encounter: an epoxy seal and an epoxy flood coat.

Epoxy Seal Coats

An epoxy seal coat is a thin layer of epoxy that gets brushed onto the project's substrate surface, usually with a paintbrush. This seals any pores in the substrate material and prevents numerous air bubbles from forming within the resin finish.

Seal coats can also be applied on non-porous substrates if the goal is to embed small items within the finish. A thick seal coat will bind to both the items and the substrate, securing them in place so that they remain positioned for the flood coat.

Sanding is almost never required after an epoxy seal coat.

Epoxy Flood Coats

An epoxy flood coat, on the other hand, is the thick, proper layer that makes up the bulk of the epoxy finish. It's poured onto the substrate surface directly from the mixing container, and involves mixing up a larger batch than the seal coat.

For additional layer, sanding is almost always recommended after an epoxy flood coat.

Sanding Is Also Necessary if You're Refreshing Your Epoxy Finish

If your epoxy finish needs to be refreshed, either because of some unfortunate damage or because it's finally reaching the end of its lifespan, you'll need to clean and sand it first.

This helps prepare the surface for a new coating, which, if applied properly to a clean surface, will mesh seamlessly with the old finish, renewing it and making it look good as new.

A wooden epoxy bar top.

Primaloc Epoxy: Premium Epoxy for Premium Results

When it comes to epoxy resin, Primaloc Epoxy gets the job done. Our epoxy resin is premium-grade, with high performance in every category, including:

  • Unmatched Strength: A Primaloc finish won't buckle, even under high pressure.
  • Long-Lasting Resilience: Primaloc epoxy lasts for many years with minimal care, and can endure high-traffic environments with ease.
  • A Crystal-Clear Coating: With its pristine, transparent appearance, looking at a cured Primaloc coating is like peering through a window.

Epoxy resin can be beautiful, strong, and long-lasting—which is why you shouldn't compromise on quality. With Primaloc Epoxy Resin, you get the ultimate finish in durability and visual appeal.

Protect your surfaces by giving them a rock-solid epoxy finish. Choose strong. Choose reliable. Choose Primaloc.


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