How to Sand Resin and Don´t Lose its Transparency

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Resin often has a perfect surface finish after it has cured but sometimes you want to remove parts from the resin or sand the resin down. I personally worked a lot with all kinds of resin and often had to sand resin as a final finishing step. In this article, I will show you exactly how to sand resin. But firstly, can resin even be sanded?

As a whole, resin can be sanded with regular sandpaper but it is highly recommended to wet sand resin to bind any harmful dust from the resin. The water will also keep the resin from melting and getting foggy as you sand it.

How to sand resin step-by-step:

  1. Fill a small bowl with water
  2. Dip the sandpaper in the water and sand the resin
  3. Use very fine-grit sandpaper to do a final pass
  4. Fix holes and deep scratches with some resin

There is a detailed step-by-step guide in the following section that will tell you exactly how to sand resin. I will show you the best way to sand resin and explain what can be done and what not to do when sanding resin.

Materials Needed for Sanding Resin

Here are the materials you need to sand resin:

  • 150 to 200 grit Sandpaper for sanding
  • 750 to 1000 grit sandpaper for the final finish
  • FFP2 mask or similar
  • Some protective gloves (latex for example)
  • Some water
  • Paper, plastic sheet, or a silicone mat
  • Some resin to fix holes and deep scratches

And that´s about it.

I recommend using wet sandpaper for sanding resin but I also wet sanded resin with regular sandpaper and didn´t really run into any issues.

You can get sandpaper at your local hardware store or right here on Amazon.

You will also need something to put the resin piece on while you sand it. You can really use anything from newspaper to a plastic sheet. I personally prefer using silicone mats because they are easy to clean and infinitely reusable. You can get them right here on Amazon.

You can get the rest of the supplies at your local supermarket.

How to Sand Resin Step-By-Step

Now that you have all of your materials it´s finally time to sand the resin!

I will show you how I sanded a small diorama that I made so that you can follow along. The whole process of the creation of this diorama is shown in my guide on how to make fake water with resin. You can read it right here.

1. Fill a Small Bowl With Water

First, let´s start by setting up our workspace.

Place a sheet of paper or plastic or your silicone mat on the worktable.

Then place your resin object, that you want to sand, on there as well.

Get a bowl of water that is big enough so that you can easily dip the sandpaper or the resin piece in it.

Then put the gloves and the mask on.

2. Dip the Sandpaper in the Water and Sand the Resin

Here you can see the diorama after I got it out of the mold. The surface was really dirty and a lot of stuff and bubbles were visible. So I decided to sand the whole surface to remove all of that.

Start with sandpaper that has a grit of about 200. This is rough enough to shape the resin piece or to get rid of any bubbles or dirt trapped under the surface.

Dip the sandpaper in the water repeatedly every few minutes to keep everything wet and to wash away the resin dust on the sandpaper.

Sand until the resin has the desired shape or the surface is free of any dirt.

You can use power tools, like a disc sander for example, to sand the resin but try to keep the speed to a minimum or you might melt the resin.

You don´t have to worry about any scratches that are visible on the surface of the resin. We will be cleaning those up in the next two steps.

3. Use Very Fine-Grit Sandpaper to do a Final Pass

We will repeat the last step but before we do we will change the water to dispose of all the resin dust and debris that is in there.

Then, we will sand the surface again but this time with very fine grit sandpaper. I usually use 750 grit to get a nice and smooth finish.

It will take quite some time to get a smooth finish but it will be well worth it!

4. Fix Holes and Deep Scratches With Some Resin

You might have some holes that were created by sanding over some bigger bubbles that were trapped right under the surface of the resin surface.

You have two choices to deal with these holes.

Either sand everything down even further until the material around the hole is gone and everything is flush or add a very thin layer of resin to the top of the resin piece to fill these holes and any deep scratches.

You can also use something similar like white crafts glue or, what I used, water texture from Vallejo.

The crafts glue and the water texture paint are both dry transparent and solid. So once they are dry you won´t see any of the holes or scratches anymore.

I would not recommend using white glue for making resin jewelry, for example, but it is a solid choice for dioramas, for example.

And then here is the finished diorama after the texture paint has dried.

How to Make Resin Transparent Again

Often, when you sand resin it will become opaque or you might have some white dust on the surface that won´t come off.

This isn´t a big issue though and can be easily fixed.

The thin white layer of dust comes from the resin slightly melting under the heat of the sanding process. Basically, the dust from the resin will stick to the surface of the resin creating this white layer of dust.

Or, if your resin became opaque during the sanding process then that is most likely because you did not wet sand it. So all of the scratches in the resin are quite rough and make the resin appear opaque instead of transparent.

No matter which one is the case the fix is always the same.

Simply use very fine grit sandpaper, around 750 grit, and wet sand the surface of the resin. It will take quite some time but after a while, you will see a noticeable difference for the better. Keep the sandpaper wet all the time, this is important or the surface might become opaque again.

Be patient, this method will take quite some time. In fact, I often need around half an hour to properly sand a medium-sized piece of resin to a smooth finish.

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