Sanding Epoxy Resin: A Full Guide

Epoxy resin is used in a wide range of projects. For example, artists pour colored resin into molds to create unique earrings or necklaces. Furniture makers might pour clear resin over a wood table to seal in a beautiful, natural look while adding a tough, protective layer. Knife makers use epoxy resin to securely bond scales to the tang. Art pieces can also be enhanced with epoxy resin, giving paintings a glossy finish that pops.

Although the results are stunning, sanding is often necessary to smooth out rough spots, get the piece ready for a final coat of paint or varnish, or repair any damage. It’s a process that requires careful work and patience: any mistakes can affect the integrity of your finished product. 

In this blog, the team atRed Label Abrasives explains everything you need to know about sanding epoxy resin, from recommended abrasive grits to the difference between wet and dry sanding. While there are a lot of steps involved, the resulting beauty and durability of the finished workpiece is worth the effort.

Understanding Epoxy Resin

Epoxy resin comes in two main types: casting and coating. Casting resin is normally used for making thick objects like jewelry because it can be poured into molds. It takes longer to harden but results in a clearer and less brittle final product. Coating resin, on the other hand, is perfect for covering surfaces like tables or artwork because it dries faster and is great for thin layers. Once epoxy resin cures, or hardens, it becomes solid and glossy, creating a durable finish that can protect and enhance the appearance of whatever it covers. 

Sanding is often necessary to remove any bubbles or bumps and prepare the surface for painting or adding another layer of resin. The goal is to achieve a smooth, even surface that makes the final product look professional and feel nice to touch. However, when it comes to sanding it down, you might face some challenges. Epoxy resin can be sticky, making it hard to sand smoothly. It also generates a lot of dust, which can be harmful if inhaled, so safety measures are important.

Wet vs. Dry Sanding

When it comes to sanding epoxy resin, you have two main methods to choose from: wet sanding and dry sanding. Both techniques are used to smooth and prepare resin surfaces, but they work in slightly different ways and serve different purposes. 

Dry Sanding

Dry sanding, where you use sandpaper or a sanding tool without any water, is the more traditional approach. It's great for the initial stages of sanding when you're removing larger imperfections or shaping the resin. Dry sanding is fast and efficient, allowing you to quickly see how much material you're removing. However, it creates a lot of dust, which can be harmful if inhaled, so wearing a dust mask is important.

Wet Sanding

Wet sanding involves using water with sandpaper or sanding tools. You either dip the sanding sheet in water or spray the resin surface with water during the sanding process. The water acts as a lubricant, reducing friction and allowing the abrasive to glide more smoothly over the resin surface. 

This method is ideal for the final stages of sanding, as it helps achieve a finer, polished finish. The main drawback is that it can be messier than dry sanding, and you have to wait for the resin to dry completely before you can move on to the next step in your project, like applying a finish.

So, which is better? It really depends on the specific needs of your project:

• Use dry sanding when you're starting out and need to remove lots of material or correct major flaws.
• Switch to wet sanding as you get closer to finishing your piece when your goal is to achieve a smooth, glossy surface.

Most of the time, you'll end up using both methods at different points in your project to get the best results.

Preparing Your Workspace

The environment where you work with epoxy resin plays a key role in how well it cures, as ideal temperature and humidity levels are necessary for the resin to set properly. Aim for a workspace with a temperature between 70-75°F (21-24°C). If the room is too cold, the resin might cure too slowly or not at all, while too warm of an environment can make it cure too quickly, leaving less time to work with it. Humidity levels should also be moderate; too much moisture in the air can cause the resin to become cloudy or introduce unwanted bubbles.

Protecting the Work Surface

Epoxy resin can be messy and once it cures, it's extremely difficult to remove. Protect your work surface with a plastic sheet or a silicone mat. These materials are easy to clean and will save you a lot of hassle if any spills or drips occur. Additionally, consider using tape to secure the protective cover in place, ensuring it doesn't shift and expose your surface to potential resin stains.

Organizing Tools and Materials for Easy Access

Having all your tools and materials within reach can make the process much smoother. Before starting, lay out everything you'll need, including mixing cups, stir sticks, gloves, and any pigments or decorations you plan to add to the resin. This organization not only helps streamline your workflow but also minimizes the risk of contaminating your resin with dust or debris, as you won't need to move around as much once you've begun mixing and pouring. 

Tools and Materials Needed

When working with epoxy resin, it’s important to have the right tools and materials for sanding and finishing can make a significant difference in the quality of your final product. Below is an overview of what you'll need:

• Sandpaper:You'll want a variety of grits, starting with coarse (like 60-80 grit) to get rid of big bumps and imperfections. Then, you'll use medium grits (100-150 grit) for smoothing out the surface more gently. Finally, finish with fine grits (200-400 grit) and ultra-fine grits (600-2000 grit) for that polished look. 
• Sanding Blocks: These are helpful for hand sanding because they give you something solid to wrap your sanding sheets around. This makes it easier to apply even pressure and avoid leaving marks on the resin.
• Power Sander: If you're working on a larger project (e.g. a table surface) or just want to save some time and effort, a power sander like a Dremel tool or random orbital sander can help you achieve excellent results. Just be careful not to sand too much off at once.
• Polishing Compounds: After sanding, polishing compounds can be used to bring out a high gloss finish. These compounds vary in abrasiveness, much like sandpaper, and are used in sequence for the best results.
• Finishing Oils or Sealants:To protect your finished piece and enhance its appearance, apply a finishing oil or sealant. These products can add depth to the resin's color, protect against scratches, and ensure your project looks great for years to come.
• Dust Mask: Sanding resin can create fine dust that isn't good to breathe in. Wearing a dust mask will protect your lungs.
• Protective Gloves:Gloves will keep your hands clean and protect them from sharp edges on the resin.
• Safety Glasses:To protect your eyes from dust and small particles, it's smart to wear safety glasses while sanding.
• Vacuum or Dust Collector:Keeping your workspace clean of resin dust is important, so having a vacuum or dust collector nearby is helpful.

Equipping yourself with the right tools and materials can help you achieve a professional finish on your epoxy resin projects. Whether you opt for power tools for efficiency or hand sanding for precision, the goal is a beautifully finished piece.

What is the Best Abrasive For Sanding Epoxy Resin?

Wet sanding requires abrasives that are specifically designed to perform in wet conditions. This means the backing of the abrasive must be suitable for exposure to water without deteriorating (like cloth or film). We specify on each of our product pages whether or not the product you’re interested in can be used for wet sanding. 

Red Label Abrasives sells orange hook and loop sanding discs with a premium waterproof polyester film backing and aluminum oxide abrasive grains. This combination not only ensures durability and resistance to water but also provides a versatile abrasive that's capable of handling both wet and dry sanding tasks. 

Our pressure-sensitive adhesive (PSA) discs are another excellent choice for wet sanding. These discs come with a waterproof polyester film backing and are available in a variety of abrasive materials including aluminum oxide, silicon carbide, and zirconia. Each of these materials is selected for its ability to deliver outstanding results in wet environments. 

Sanding Epoxy Resin With a Sanding Block

Sanding epoxy resin with a sanding block is a simple, effective method that offers good control and even pressure. This technique is especially useful for beginners or those working on smaller projects where precision matters. To use a sanding block, take the following steps:

• Begin with a lower grit waterproof sanding sheet(around 80-120 grit) attached to your sanding block. This coarse grit helps remove any major bumps, drips, or imperfections from the cured resin.
• Sand the resin surface using gentle, circular motions or back-and-forth strokes. Ensure you cover the entire area evenly, applying steady pressure throughout.
• Once the major imperfections are smoothed out, switch to medium grit sanding sheet (180-220 grit) to refine the surface further. After smoothing with medium grit, move on to fine grit sandpapers (320-400 grit) for an even smoother finish. If you're aiming for a highly polished look, you can continue to ultra-fine grits (600-2000 grit).

It's important to remove any dust or residue from the resin surface before switching to a finer grit. This can be done with a damp cloth or by rinsing with water, depending on whether you're wet or dry sanding.

Using a sanding block is a straightforward and effective approach that can lead to professional-looking finishes, especially when you carefully progress through the grits and ensure the surface is clean and even at each step.

Sanding Epoxy Resin With a Random Orbital Sander

Using a random orbital sander is the most popular method for sanding epoxy resin. The random orbital motion minimizes the chances of creating swirl marks or uneven surfaces, which are common issues with other sanders. Many models also support attachments for dust bags or dust extractors, helping keep your workspace clean.

This method requires the use of sanding discs. Once you’ve assembled all your tools and prepared your workpiece, take the following steps:

• Begin sanding using the lowest grit (120-grit if starting from scratch or 400-grit for light scratches), applying the "right-to-left, top-to-bottom" technique. This method involves overlapping each pass by about half, ensuring full coverage. Move slowly to sand the tough epoxy.
• After using the coarse grit, wipe down the surface and inspect for scratches. Move to the next grit size (180-grit), marking the surface with a permanent marker to track your progress. Repeat the sanding process, alternating between horizontal and vertical passes to minimize scratching.
• Once you've addressed any deeper scratches, move on to finer grits (400-grit, 800-grit, and then 1200-grit). For the 1200-grit phase, switch to wet sanding by lightly misting the surface with water to prevent dust and clogging. Complete several passes with each grit, wiping down the surface between passes.

After completing all sanding passes, inspect the surface for any remaining scratches. The final 1200-grit pass should leave your epoxy resin smooth and ready for polishing, without any visible scratches.

Avoiding Common Sanding Mistakes

Several common sanding mistakes can compromise the quality of your epoxy resin finish. Here are some missteps you’ll want to avoid:

• Over-sanding, or removing too much material, can create dips and uneven surfaces. To avoid this, use even pressure and regularly check your progress. 
• Uneven pressure, another common mistake, can result in an inconsistent finish. Always ensure you're applying consistent force across the entire surface. 
• Rushing through the grits or skipping sizes can leave deeper scratches that are hard to remove later. Take your time to work through each grit incrementally for the best results.

Applying a Finish: Choosing Between Oils, Sealants, and Varnishes

The right finish depends on what you want to achieve:

• Oils can enhance the natural beauty of the resin, giving it a soft, warm sheen while providing some protection. 
• Sealants, such as epoxy resin sealants, offer a layer of protection against moisture and can be ideal for pieces that will be handled frequently. 
• Varnishes provide the most durable finish, protecting against scratches, moisture, and UV rays, and are best for pieces that will be exposed to harsher conditions or need a high-gloss finish. 

Each type of finish has its own curing time, ranging from a few hours to several days. It's important to follow the manufacturer's instructions for the best results. During this time, keep the project in a dust-free environment to prevent imperfections. After the finish has cured, you may want to apply a polishing compound for an extra glossy shine or simply enjoy the natural look of the cured finish. For long-term care, keep your epoxy resin project away from direct sunlight to prevent yellowing and clean it with a soft, damp cloth, avoiding harsh chemicals that could damage the finish.

Troubleshooting Common Sanding Issues

Sanding epoxy resin is a critical step in achieving a flawless finish for your projects. However, even with careful planning and execution, you might encounter a few common issues. Here's how to address them.

Correcting Cloudiness or Dull Finishes

Cloudiness or a dull finish can be caused by several factors, including moisture trapped during the curing process or sanding too aggressively with coarse grit sandpaper. To restore clarity and shine, begin with fine grit sandpaper (around 600 grit) and wet sand the surface. This will help to remove the top layer that contains the cloudiness or scratches. Gradually move up to ultra-fine grit (up to 2000 grit), keeping the surface wet to minimize dust and scratches. Finish by applying a polishing compound and buffing the surface to a high shine. 

Repairing Accidental Gouges or Deep Scratches

Accidents happen, and sometimes your resin might end up with gouges or deep scratches. To repair these, clean the area thoroughly and then fill the gouge or scratch with a new layer of epoxy resin. 

If the scratch is not too deep, you can also try to sand it out starting with a medium grit sandpaper and working your way up to a fine grit, followed by polishing. For deeper repairs, after the filler resin has cured, begin sanding with a medium grit to level the repair with the rest of the surface, and then proceed through finer grits to blend the repair seamlessly into the surrounding area.

Get Your Epoxy Sanding Discs & Sheets From Red Label Abrasives

Mastering the art of sanding epoxy resin is essential for achieving a smooth, glossy finish. From selecting the right abrasive grits and tools to understanding both wet and dry sanding, each step plays a critical role in the final outcome. 

At Red Label Abrasives, we offer a wide range of high-quality sanding belts, sanding discs, sanding sheets, and other abrasive products designed to meet the demands of any project, big or small. Our expert team is always ready to provide advice and support, helping you choose the perfect abrasives to achieve outstanding results. If you have questions or would like to place an order, please contact us by calling 844-824-1956 or filling out our contact form today.