You don’t need a workshop filled with lapidary equipment to polish stones. As long as you’ve got your trusty Dremel or any other rotary tool, you can get your stone smoothed out and shining.
So, without further ado, let’s hop right in and we’ll show you how it’s done.
An Easy Guide to Polishing Stones With a Dremel
Before you begin, you’ll need to have the right tools and protective gear for the task.
As far as tools, you’ll need the following:
- A Dremel or other rotary tool
- Diamond grinding wheels and burrs
- Sanding drums or Discs up to 1000 grit
- Felt polishing wheel
- Rock polishing compound
Choosing Your Dremel
Any Dremel or rotary you have on hand is capable of polishing a stone with the right accessories.
Here are a couple of recommendations if you’re purchasing one.
The first is to ensure you have variable speeds. Working stone is a low RPM affair, and a high-low switch or single-speed motor will make things harder.
You should also look for a model compatible with a flex shaft. Dremel makes a branded one for their tools and they work better than a standard configuration. You can remove the risk of electric shock by placing the Dremel away from your water source while cutting. The handpiece is also more maneuverable than the rotary tool itself.
Battery-powered Dremels are a favorite, but extensive work can take more than one charge. If you’ve never worked rocks, you’re going to find out that extensive work is much smaller than you think.
Protecting Yourself While Polishing
Grinding stones is a bit hazardous, even when you’re working by hand. Your Dremel is going to throw off a lot of dust, and most of it is bad for your lungs.
In some cases, such as agate, you’ll be creating ultra-fine particles of silica that can lead to silicosis over time. Others can lead to more immediate consequences, like the arsenic in Bumblebee Jasper. In any case, it’s best to avoid dust as much as possible.
Wherever you’re working needs good ventilation. Outside is best, but it’s not possible for everyone.
You should also use a mask, even if you’re working outdoors. Don’t use a regular dust mask, they’re meant for sawdust and large particles. You’ll need at least an N95 rated mask, and you’re best off with a half-face respirator with the appropriate filters.
To keep the dust levels low, you should work stones wet. You can use a drip system or dunking the stone in water repeatedly. If you have access to a flex shaft for your Dremel you can work them directly in the water.
If you’re using a corded Dremel be careful. Even if you’re far from the outlet, it’s a good idea to create a drip loop to avoid water running down the cord. All you have to do is make sure there’s a looped segment lower than the outlet.
Safety glasses are a must. Stones can chip unexpectedly and the resulting stone can damage your eyes. Use an ANSI-rated pair.
If something gets around your glasses, don’t touch your eye. Stone splinters will cause a lot more damage. Take a hint from Ishi and pry open your lids before thumping yourself in the back of the head. It’s undignified and a bit painful but it works. If it doesn’t, get yourself to the local ER.
This isn’t a particularly dangerous task, the hazards are easily avoided with some basic protective gear. As long as you’ve got a mask and goggles you’re good to go!
If you have your tools and PPE together, then you’re ready to get started.
How to Polish Stones With a Dremel
Step 1: Clean Your Rocks
If you haven’t already, you should get your rocks cleaned.
Since we’re going to sand, and possibly grind, the stone it’s not important to get them shining. The dust from the stone is more hazardous than any dirt the Dremel might send airborne.
A bucket with warm soapy water and a wire brush will do the trick. For soft stones, a stiff nylon brush may be better. On the other hand, you’ll be grinding any surface scratches a wire brush will create.
Pay special attention to deeper crevices. The dirt build-up can hide fractures that need to be ground out.
Once they’re clean, it’s time for the fun to begin.
Step 2: Grind to Shape
Diamond grinding wheels and burrs will let you shape the stone.
Keeping the stone wet, grind the stone into a rough shape. You can hold smaller stones in your hand if you’re careful with the Dremel, larger stones may need to be held in a vise.
Grinding will rapidly remove water from the stone’s surface. You’ll need to wet the piece frequently or it will begin throwing off a lot of dust. It can be tempting to just grind through, but you’ll get a rougher finish and make a mess.
For those just trying to get a “tumbled” look, this step will take less time. Use ball burrs to open crevices and remove fractures, and use the grinding wheels for bringing down sharp corners and removing fractured material. The last bit is important: you may lose some stone, but a heavily fractured piece will fall apart in your hands when you get to sanding.
While grinding, you should use a low speed on your tool. Lower is usually better, but you’ll be fine as long as the bit isn’t slinging mud. If a stone is getting too hot to handle, it’s a good sign to lower RPMs.
Use a light touch. Diamond bits burn quickly when you’re pressing them down. A light touch and low RPMs will make them last much longer. But, even with best practices, diamond burrs are disposable. Sooner or later the grit wears off or the diamonds burn, it’s just part of the process.
Some people cut cabochons with a Dremel. It’s a little bit outside of the scope of this article, but all you need is a set of diamond-cutting wheels. Most cabochons will go through a more intensive shaping and polishing process, but the basics are the same as polishing a specimen.
If you’re not carving a particular shape, the most important thing is that the stone has any unstable portions removed through grinding. After that, it’s just a matter of aesthetics.
Once you’re happy with the shape of your stone, you’re ready to move on.
Step 3: Sanding
Sanding the stone is a matter of patience.
You should begin with a lower grit, something in the range of 400 is a good start as long as you ground the stone to your liking. Anything lower will remove a lot of material, a 200 grit drum does well for final touches but lower than 200 grit isn’t advisable. Go back to the diamond if 200 grit won’t make the adjustment.
Then it’s a matter of smoothing the surface of the entire stone evenly. It can take a lot of time depending on the size of the stone, but you need to work methodically.
Letting the stone dry and rubbing off the dust with a microfiber cloth is a good way to figure out if it’s time to move up in grit.
For a complete newbie, I recommend covering the entire stone in Sharpie or another black marker. The ultra-thin layer of ink will be removed easily, and you’ll know that you’ve sanded that portion of the stone.
Lower grits will leave a distinctive scratchy pattern. This comes out with the next grit, and it’s a reliable indicator of how far along you are.
Keep the stone wet while sanding. Dip the stone as soon as you see dust starting to come off.
Work progressively to higher grits. Most sanding drums and discs are spaced apart by 200 grits, which is ideal. Run from 400-1000 or 1200 depending on what you have on hand.
Optional: Hand Sanding
For a better finish, you can also hand sand the stone once you’re beyond 1000 grit and before polishing. We recommend it for cabochons, but it’s not required for polished specimen pieces.
Begin hand sanding at 1500 or 2000 grit. You can find sandpaper up to 5000 grit online, but most hardware stores top out at 3000.
Hand sanding can be tedious but just move to the highest grit you have. At this point, you’ll usually be going up by 500-1000 grit between jumps. Expect to spend at least a few minutes with each grit.
Going over 2500 isn’t required in most cases, but it’s an option for perfectionists.
Step 4: Final Polishing
With the stone properly sanded down, you can create the final polish.
You should remove sanding dust before proceeding. It can lead to small scratches on the surface of your stone as the grit gets moved around. A microfiber cloth is good for removing the fine dust on the rock after sanding.
For most stones, the recommended polishing compound is cerium oxide. It most often comes in the form of a powder. You’ll need to create a paste to apply it to your wheel.
Just mix it with a bit of water to apply it. If you don’t have a felt polishing wheel for your Dremel, you can also apply this paste to a piece of cloth for polishing. Hand polishing is… trying, however, and it won’t achieve better results.
Use the Dremel at a slow speed, you shouldn’t be flinging paste all over. Apply it to the stone and move the wheel over the surface. You’ll also want to move the wheel in small circles as it goes, rather than trying to run it straight across.
Once you’re done buffing, you’ll have a piece you can be proud of!