Rotary Rock Tumbling: Get Rolling

Part 5 of 6 – It’s time to get rolling!

You’ve done it! You have made through our first four sections on getting started, choosing material, loading the barrel, and adding water and grit and not it’s time to fasten that barrel lid in place and start rolling. Before you do please make sure to read through this list of pro-tips, tricks and advice which starts off with a ‘generic’ four stage tumbling cycle packed with specific information from our expert rock tumbling community members.

Before we get to the “Get Rolling” list of pro-tips, tricks and advice, what follows is a description of a rotary rock tumbling cycle through which a batch of rocks comparable to agate or jasper can be reliably transformed into gorgeous polished rocks every time. Please consult a recipe specific to the size of your tumbler for the actual measurements of how much grit to add to your barrel at each step of the cycle.

  • Stage 1 – Course grind with 60/90 SiC with no time limit.
    Check the rocks and recharge the grit weekly until every rock in the barrel is ready to move on free from pits and major cracks that will be impossible to clean the grit out of. Don’t be afraid to cull out problematic rocks during this cycle. Much more is said about stage 1 rough grinding in the tips and advice below, so take the time to keep reading for now.

  • Stage 2 – Medium 120/200 SiC for one week.
    Check the rocks and remove any new problem rocks that have appeared. Medium tumbled rocks that are ready to move on should have a very finely abraded (dull) surface and they should feel very smooth but not look it. If you did a very careful job on stage 1 getting every rock in the batch ready to move on, you probably won’t need to keep rolling on stage 2 after one full week. That being said, with the amount of rock material lost on this step being substantially lower than on stage 1, don’t be afraid to recharge grit and keep going if you think it needs it.

  • Stage 3 – Fine 500 SiC for one week.
    Check the rocks again and remove any new problem rocks that have appeared. Fine tumbled rocks of a hard material like jasper or agate should be very smooth and starting to show a patchy shine. Again, never be afraid of recharge and go another week if you think they are not ready.

  • Stage 4 – Polish with *AO powder for one week.
    Check the rocks and if you have followed these steps carefully and patiently you should be looking at a beautifully polished rocks that have reached the full potential of the material.

*As a side note of caution, certain materials do not respond well to aluminum oxide (AO) polish so you might have to venture out of your comfort zone and experiment with other polishes such as tin oxide or tripoli for the final polish.

What follows next in no specific order is a bullet list of pro-tips, tricks and advice on the subject of getting your rotary rock tumbler rolling, contributed by the Rock Tumbling Hobby Forum community.

  • Before getting rolling it is a great time to start recording the steps you take including photos of the rocks before they started in the stage, date the stage started, grit/polish amount, description of content etc. This can be anything from keeping a notebook to using your phone or other device app to record the information. Recording and photographing all of this makes for a great batch report for us to admire and learn from when posted as a new thread on the Rock Tumbling Hobby Forum.
  • After closing and sealing your tumbler lid and starting the tumbler rolling, it is wise to recheck everything 15 minutes or so after it starts rotating just to make sure you have sealed the barrel securely and now is the time to fix any leaks that might be showing.
  • After two to three days of running a newly loaded tumbler barrel, it’s a good idea to open the barrel and check to make sure a good thick slurry has developed, completely coating all of the rocks. If you can still see the actual colors of the rocks, add a bit more grit (and a spritz of water) and check it again in a couple of days.
  • When opening the barrel gently insert the edge of flat screwdriver or a washer between bottom lip of lid and where it meets barrel and turn to break the seal. Anytime you have opened the barrel you can place the washer back on the inner lid post and start the nut on the screw thus making them easy to find.
  • Checking the barrel as mentioned in the previous tip also serves to let off any pressure that might have built up, thus avoiding a barrel blowout.
  • Don’t skimp on the amount of time stage 1 rough grind takes. Regardless of what the recipe you are following says, rough grind should not have an assigned timeline, and should not be rushed.
  • Stage 1 rough grind is the best time to thoroughly cull out bad rocks that cannot be saved because they have irregular shapes or pits, cracks or soft spots, that are so deep they can not be ground away. Upon examination of the tumbled rocks, the rough grinding stage should be culled and repeated as often as necessary until all of the stones have achieved the shape you are looking for and all of the imperfections have been removed.
  • When inspecting, allow your stones to dry out completely so you can see any flaws that would be invisible when the rocks are wet.
  • It’s important to remember that as you continue on with rough grinding, the overall size of a stone will have to be reduced to the depth of the deepest pit on the stones you are trying to fix, and choosing instead to cull out a cracked or pitted stone might be the best solution for the sake of the rocks in the load that are already perfect in quality, shape, and size.
  • Another idea to go along with the above tip is to cull out the ‘perfect’ rocks and keep adding rocks that need more work to remove imperfections until you have enough of a collection of perfect rocks to continue on to the next step of the cycle. As you can imagine, this method adds a significant amount of time to the overall tumbling cycle.
  • If new rocks have been introduced to replace any of the rocks that you have culled out, remember that this restarts the cycle for all of the rocks in the barrel, which probably is not a bad thing. Rough grind should only be considered finished when your tumbler has produced a bowl of beautifully shaped rocks that do not have any irrecoverable flaws as mentioned in the previous tip.
  • As was mentioned above, rough grind is about keeping the rocks in a waterfall motion, suspended in a thick slurry of fresh grit so that shaping and grinding occurs fairly quickly. As you progress through towards the latter stages it becomes about slowing the rocks banging on rocks action down, to reduce bruising, chipping, or breaking . To achieve this we use some type of media between the rocks so they don’t hit each other as hard.
  • Be creative and experiment by adding as many stages as you think the rocks need – some experienced tumblers like to run a 1000 AO grit stage in between 500 and final polish.
  • It is wise to use a piece of masking tape to write on with a sharpie, on the top or bottom of the barrel that identifies what is currently in the barrel and when it was started, or any other data about the barrel that helps you remember where you are at with it. This is especially important if you have a multiple barrel tumbler, or multiple rock tumblers running. You might think that it will be easy to remember but trust us on this, it’s not.
  • Borax is an excellent detergent booster and is often used as a one or two day tumble cleaning between grit stages. Some tumblers use it between every stage and others before they switch to final polish – and maybe again after final polish.
  • Devote separate media or plastic pellets for all stages if you can, including Borax cleaning stages. Some tumblers even use separate cleaning buckets for every stage to avoid grit contamination.

Now that your tumbler is happily rolling, lets take a look at the final Part 6 of the series, Rotary Rock Tumbling Cleaning Up, and start thinking ahead to what you will need to make your final cleanup efficient and maybe even enjoyable.

If you would like to offer feedback about your own experiences, pro-tips, tricks and advice, please post in this thread in the Rock Tumbling section of the RTH Forum, and they might eventually make it into the appropriate category in this article series.