Sanding epoxy resin can be an arduous task if you lack certain tools or knowledge.
In this Primaloc Guide, we'll be explaining what you need to sand and how best to go about it.
Why Do We Sand Epoxy?
To smooth out a surface is often the primary goal of sanding.
There are various reasons why someone would sand their epoxy surfaces, such as:
- To correct a mistake. Maybe while pouring your epoxy, some of it didn't flow onto the surface evenly, or it was disturbed while curing.
- To prepare a surface for polishing.
- To prepare an epoxy surface for an additional coating of epoxy.
Other reasons exist as well, but these three are the most common.
Is Sanding Epoxy Difficult?
It's certainly time-consuming—maybe even tedious, if you're going the extra mile. But it's usually worth it.
For an epoxy resin finish, sanding can take quite a while. Epoxy is incredibly durable, and its resilience actually works against you when sanding. The stronger the epoxy, the more challenging it will be to sand it.
Using the proper tools and techniques will make this task much more manageable, though. Notably, you can complete the entire sanding process over multiple sessions; it doesn't need to be completed in one.
When it comes to sanding, the first thing to consider is safety. Some basic precautions will keep you from breathing in any particulates that the sander you use stirs up into the air.
Always wear a face mask/respirator—N95 or KN95 suggested—when working with a sander.
Wet and Dry: The Two Methods of Sanding
There are two contemporary methods for sanding: wet sanding and dry sanding.
Wet sanding for epoxy involves dampening the epoxy surface first, then using an appropriate sanding pad, which will collect the wet dust as it's generated. This method kicks up much less dust into the air.
Dry epoxy sanding, on the other hand, is sanding with an appropriate abrasive on a dry epoxy surface. This method tends to add more dust to the air (which does eventually settle, but is unpleasant in the mean time).
We'll be recommending a mixture of wet and dry sanding for optimal results.
How to Sand Epoxy Resin
Step #1: Acquire the necessary supplies.
You'll first need some basic tools and supplies. Here's a list for a typical epoxy sanding endeavor:
A random orbital sander. This power tool will make smoothing your epoxy much easier than manually efforts. A 5-inch or 6-inch sander are both fine. Make sure any of the disposable attachments you obtain work for the sander you've chosen.
Hook-and-loop sanding discs. You'll attach these to your sander to grind down the epoxy surface. You'll want a variety of grits, as the sanding process will start low and gradually rise to higher, finer grit levels.
We recommend 120, 180, 240, 400, 800, and 1200-grits.
If you just need to sand a lightly scratched epoxy surface, you can also just use 400, 800, and 1200-grit discs.
Regardless, you'll want 1 or 2 of each, depending on the size of your project. For instance, a large bar top will likely need 2. An ordinary table top, probably 1.
A spray bottle filled with water. This is for dampening the surface before you start wet sanding it.
Microfiber cloths. These are great for cleaning the surface after each pass to prepare it for the next one.
A dust extractor or dust bags. These can pull dust out of the air. This can be considered optional, but it's quite nice to have.
- A black permanent marker. This will help you keep track of your sanding. The marker goes on the surface, then the sander grinds it away. If you still see marker after a pass, it means you didn't grind it down enough.
Step #2: Set Up Your Workspace.
Gather your tools and supplies, placing them in convenient locations so you can quickly reach them as needed, but where they won't be in the way (to avoid knocking them down or causing any issues).
If you have a dust extractor, make sure it's set up. If you're using sand bags, make sure one is attached to your sander.
Step #3: Sand the Epoxy Resin Using, Starting With Low-Grit Discs
At this point, it's time to sand. Keep your mask on for this process to avoid inhaling any epoxy dust.
RLTB Sanding Technique: "Right to Left, Top to Bottom"
Our sanding method involves the "right to left, to to bottom" technique—a long name with a simple premise.
You start sanding form the top-right corner. Slowly move it toward the top-left corner. When you get there, bring it down a little—about half the width of the sanding disc—and go back toward the right.
By overlapping each streak about halfway with the previous one, you can ensure you don't miss a strip of surface.
When you're sanding, move the sander slowly, about one inch a second. This gives the tool time to work on the resilient epoxy surface.
Repeat this process until you've done an entire pass. Also, after each pass you'll rotate the directions you move in. So for the second pass, you'll move top right to bottom right, move left about half-a-disc length, then slowly sand upward. Repeat this like you did with the previous pass until you reach the end.
For mixed material surfaces (a rare situation), such as a river table with wood that has no epoxy seal, you'll move more quickly while over the other materials, as they're less durable and won't need as much time under the sander.
After a pass, you'll check to see if the scratches have been replaced with newer, fine scratches. If not, do another pass. If so, you're good to move onto your next grit level.
Sanding Instructions (Skip to the 400-grit step for light sanding)Start with the 120-grit.
- Do the RLTB technique mentioned above for each pass.
- After a pass, you should wipe the surface down with a microfiber cloth to clear away dust. Check your disc occasionally to see if it needs to be washed/replaced. It's not good to sand with a clogged disc.
Next up is the 180-grit disc.
- First mark your surface with the black marker, making some zigzag lines on the epoxy surface. These will help you track your progress—i.e., if the line is visible, you didn't sand that spot enough. Do this in a wide pattern over epoxy surfaces only. When the sander grinds the epoxy enough, the lines will have been removed.
- Do 5 more passes with the same RLTB technique from earlier. After each pass, mist the surface and wipe it down, then apply new marker lines.
- Examine your surface, the new scratches should be even lighter, indicating that they're from the 180-grit disc. If not, you can do another pass and check again. Otherwise, it's time to use the 240-grit.
Next, you'll use the 240-grit.
- It's actually the same process as for the 180-grit. Mark the surface, do a pass, clean the surface, repeat.
- You'll do another 5 passes here. Remember to take it slow to achieve optimal results.
At this point, switch to the 400-grit disc.
- Mist the surface and wipe it with a microfiber cloth. Use the black marker to apply zigzag lines to your epoxy surface (just epoxy, not wood or any other material).
- Use the RLBT technique to do a pass.
- After each pass, repeat these steps. You'll do 7 passes for this one.
- Note: There shouldn't be any significant scratches at this point. If you see some, you'll need to return to a lower grit and work your way back up to 400-grit.
From here, it's time for the 800-grit disc.
- Repeat the same process as above (for the 400-grit). 7 passes total.
- Then move to the 1200-grit
Finally, the 1200-grit disc.
This one is a little different and will include wet sanding. Put the marker aside, you won't need it anymore (water and ink make a mess).
- Wipe the surface with your microfiber cloth.
- Mist it with a spray bottle. You want the surface wet for your 1200-grit wet sanding disc.
- Do 4 passes, then examine the surface. It should not appear scratched anymore—i.e., the scratches are so fine that they're practically imperceptible at this point.
At this point, you're finished! You should have a well-sanded epoxy surface. It's also ready for polishing at this point, if that's your goal.
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