Rock Tumbling Secrets

Rock Tumbling Secrets

Want to get a great tumbler with grit for one complete tumbling, plus RockMan Pat’s secrets for tumbling? Click here!

Rock Tumbling Secrets

There is a beach out on Whidbey Island (that’s in Puget Sound here in Washington state) that we love to take groups to in order to find the best assortment of stones and rocks for their collections or to study. We can find agates, lavas, serpentinite, quartzite, jasper, and so many others. And these rocks have been tumbled by the ocean, and are so shiny and smooth! At least, while they are still wet.


But as soon as they dry off, they are dull, not even beginning to exhibit the brilliance of when they were wet. This is so often a disappointment to the kids, as they pick their samples with such care as to color, shape or size. But especially color.

The quickest solution to this is to give them a good coat of shellac or polyurethane that makes them appear to be polished. The more permanent solution is to tumble them yourself to get that glorious shine!

Rock tumbling can be a very fun hobby. Many folks have tried it, and almost as many have quit. It takes time, and many kids don’t want to wait 5-8 weeks for results! And there are tricks to getting it right, and often the instructions that come with your tumbler aren’t very clear about that. So with that in mind, and if you are one of those that wants to tumble rocks, here are some pointers for you!

Get a good rock tumbler!

Don’t spend your money on a tumbler from a craft store, or even one of those that you can find in a museum. These are noisy, and often made of very inferior material that breaks easily. They may be good for one or two batches of rock tumbling, and then you are out of luck. We would recommend that you get one that has a rubber barrel to cut down on the noise that is generated. And get one from a reputable maker. We suggest Lortone, among others. You can get one from us here, along with enough grit to get you through your first batch of stones.

Where to put the tumbler?

We would suggest that you put the tumbler somewhere that won’t drive you to distraction. If you followed our advice and got a tumbler with a rubber barrel, then it may actually produce a rather soothing white noise. But soothing or not, we keep ours in the garage. You should also consider if it is convenient for you to get to in order to tend to it. It should not be out of sight, out of mind. That could be a mini catastrophe waiting to happen!

How do I choose rocks to tumble?

You need to choose rocks that are the same hardness for each batch that you do. If you are not familiar with this idea, be sure to look up what is the relative hardness of the stones you are tumbling. And be aware that some stones, like obsidian, are just too soft to tumble. You will have nothing left if you tumble them.

Also, mix the different sizes of stone. Small, medium and large. And mix jagged with smooth. You want to fill your tumbler about ¾  full. When you finish the whole process, a good deal of the stones will have been ground away, leaving the barrel only about half full. This is normal.

The First Step in Rock Tumbling

After you have selected your stones to polish, put them in the barrel, and fill the barrel with water to the top of the stones, and add the grit. After putting the stones in the tumbler, along with the appropriate grit, then you wait. I would suggest 10 days for each stage. You will clean out the grit at the end of each stage, and then put in a smaller grit and repeat the process. You will do this several times before you get to the finished product. And always be sure to clean out the barrel and the stones completely after each stage. You will go through three stages of tumbling, with three different grits,  before you get to the polish stage.

Cleaning the grit out after each step is important!

First, don’t run the grit down your sink. That could be a costly plumbing bill, as the grit could harden in your pipes. Find a good place outside to rinse the grit, using a garden hose. And be sure to be very thorough. Any leftover grit in your stones will etch them as they go through the next phase. Your barrel, as well as the stones, need to be completely free of any residual grit.

The Pre-Polish Stage

Now, before proceeding onto the polish stage, examine the stones for the “smoothness” factor. If you are satisfied with the smoothness of the stones (they should feel satiny, but have a dull finish), then place the stones into the barrel and again fill with water to the bottom of the top layer of stones. If, however, you are not satisfied with the smoothness of the stones, replace the stones and repeat this most recent (pre-polish) stage. This stage is crucial, as it sets up the stones for an effective polish. Add the appropriate pre-polish grit and tumble again continuously for 10 DAYS. If you are satisfied, go on to the next step. Be sure to remove any broken stones. Carrying them forward will scratch the other stones. They can be tumbled again in the next batch of stones.

The Polish Stage

Now, here is what you have been waiting for, the stage when you put a shine on the stones. After cleaning the barrel and stones thoroughly, place the stones back into the barrel, fill with water to the bottom of the top layer of the stones and add the appropriate amount of polishing grit. At this stage, you may have found that there is quite a bit of room left in the barrel. What now? Use some kind of media like small wooden pellets or plastic beads to fill some of the space. The media will help carry the polish and also assure that your stones will not be scratched or damaged during the polish stage. If you only use this media for the polish stage, there is no need to clean it between batches. If you need media for your previous stages, use new or different media.

Tumble the stones on the polish stage for 10 days. At the end of this stage, take out a few of the stones, rinse them and check the shine. If you are satisfied with the shine, then you are ready for the burnishing stage. If you are not satisfied with the shine or the stones are dull in appearance, you will have to go back to the pre-polishing stage and repeat that stage. More polish will not help! More time will not help! The pre-polishing stage must be repeated. Be sure to clean your barrel thoroughly, as a dirty barrel may have contributed to the problem.

The Burnishing Stage

When beginning this stage, it is not necessary to clean the barrel or stones. Simply dump as much of the polish liquid as possible (not down your sink!), and then add water up to the bottom of the top layer of stones. Clean the lid and seal of the barrel so that there will be no leakage, and dry thoroughly. Before replacing the lid, add one cup of plain Tide powder detergent. Do not use a liquid detergent, as this will ruin your polished stones. Liquid detergent will scratch the newly polished stones! Reseal the barrel and let tumble for a day or so. Burnishing helps clean the stones and puts that extra shine on them. Remove the stones and enjoy what you have waited so long to appreciate! Then do it again.

And there you have it! Rock tumbling made easy!If you have specific questions, don’t hesitate to contact us for some sage advice!

To purchase a 6-pound Lortone tumbler, with the grit you need for one tumbling, as well as our secrets for tumbling, click here.

Leave a Reply

Your email address will not be published. Required fields are marked *

Join the Northwest Treasures Newsletter!

When you join the Northwest Treasures newsletter, you get our monthly newsletter, which includes a video Geo Talk, as well as announcements about specials and upcoming events. Be the first to know about our Yellowstone Creation Adventures, or our summer camps!

By submitting this form, you are consenting to receive marketing emails from: Northwest Treasures, 18421 10th Drive SE, Bothell, WA, 98012, You can revoke your consent to receive emails at any time by using the SafeUnsubscribe® link, found at the bottom of every email. Emails are serviced by Constant Contact