How to use a Vibratory Tumbler for polishing rocks
Tumbling rocks in a vibe tumbler is a bit different to using a rotary tumbler so please see the following instructions to get you started:
Vibratory tumblers work much faster and are cheaper to run than Rotary tumblers. As a guide, you can expect to polish a batch of rocks in around a quarter of the time required in a Rotary tumbler. Apart from the time saving, vibratory tumblers also use significantly less grit or polish to process a batch of rock.
Vibratory tumblers do not significantly change the shape of the rough rock but rather smooth the surface. By contrast, the tumbling action of a Rotary tumbler produces a much more rounded shape.
Vibratory tumblers generally work faster and use less grit. However, they do require more active monitoring while the batch is being processed. The principles are quite simple though so please use following instructions as guide when operating your new tumbler.
Safety:
- Always connect the tumbler to a properly grounded power outlet on a circuit with an earth linkage safety switch installed. Check power cord and plug before each use.
- Do not cover the tumbler with a blanket, box or similar cover to reduce noise - this reduces air flow to the motor and may cause overheating and increased fire risk. The motor will run warm to the touch - this is normal so make sure air flow is not restricted.
- Vibratory tumblers may "walk" if not on a completely flat surface. If this happens, you may need to block or "fence" the tumbler in on a workbench. Using a rubber mat can help to stabilise the tumbler. Do not operate unsecured on a bench if tumbler is at risk of falling off.
General Set-Up and Instructions:
In addition to your tumbler, you will need to source appropriate grit, polish and/or other media as required for your job. We recommend porcelain (non-abrasive ceramic) shapes as filler media rather than plastic pellets as these react better to the vibratory action of these tumblers.
For tumble polishing rocks, we generally recommend 3 to 4 step process. You may be able to skip one or more of the earlier stages if your material is very smooth and partly processed. The following is one example of a 4 step process – depending on your material, you may adjust this procedure.
- Step 1- Medium Grind - Silicon carbide Grit #220 - ½ to 1 tablespoon per kg of rock
- Step 2 – Fine Grind - Silicon carbide Grit #400 or #600 - ½ to 1 tblsp per kg of rock
- Step 3 – Pre-Polish – Silicon Carbide #1200 or Aluminium Oxide #1500 - ½ to 1 tblsp per kg of rock
- Step 4 – Polish – Cerium, Aluminium or Tin Oxide - ¼ to ½ tablespoon per kg of rock
Optional Preliminary Step - Coarse Grind:
Using #80 grit is not recommended in vibratory tumblers as the aggressive action can lead to premature wear of the bowl. Some may like to tumble rocks in a rotary tumbler with #80 as a preliminary step to get the stones nice and rounded with all rough edges removed before tumbling in the vibratory tumbler. Clean the rocks very thoroughly before moving on to the Medium Grind Step.
Step 1 - Medium Grind:
Start by loading clean rocks into the bowl, filling it to within about 3/4 full or 3-5cm from the top. You may add some porcelain shapes if you do not have sufficient rough to fill the bowl to the optimal level.
Fill the bowl with water to wet the rocks and the inside of the bowl and then drain all the water. You are aiming to have the rocks wet so that the grit sticks to them and forms a slurry but not have excess water which will wash the grit from the rocks. Look for a constantly rotating action where the rocks move in towards the centre of the bowl as they rotate around in a circular motion.
Add about half to one tablespoon of #220 silicon carbide grit per kilogram of rock added to the bowl. The tumbling action of the rocks removes material from the rocks and a thin layer of "mud" begins to build up on the surface of the rocks. After about 12 hours, stop the tumbler and rinse the rock by filling the barrel and draining the muddy water out a few times. Reload the bowl with new grit and run for another 12 hours.
IMPORTANT NOTE: When you rinse the rock don't allow the slurry to go down the drain - it can clog your plumbing! Better to dump the rinse water into a bucket, allow the grit/mud to settle, pour off the clear water, and dispose of the dry grit/rock residue.
After 24 hours of tumbling the rocks should be ready for the next step. Instead of stopping the tumbler now, for easier rock cleaning, remove the lid and add a few drops of liquid dishwashing detergent to the bowl and a small amount of water. The soap and water form a froth that washes the grit and mud from the rocks - run for another ten to fifteen minutes until the mud slurry starts to come away from the rocks. Stop the tumbler, remove the barrel and thoroughly clean the rocks and the bowl - be sure to clean away every speck of grit and mud.
OPTIONAL BURNISH STEP: Run the clean rocks in a soapy water mix for another 15 minutes as a "super-wash" step before proceeding to the next stage.
Step 2 - Fine Grind:
After the rocks and bowl are thoroughly clean, return the rocks (and clean porcelain shapes if you need them) to the barrel, fill it with water, turn it upside down and allow the water to drain. Add about half to one tablespoon of #600 silicon carbide grit per kilogram of rock added to the bowl and tumble for 12 hours. At the end of 12 hours, stop the tumbler, rinse the rock, reload with grit and run for another 12 hours.
After 24 hours of tumbling with #600 grit the rocks should be ready for the polishing step. Repeat the ten to fifteen minute wash with dishwashing liquid and some water and then clean every speck of mud and grit from the rocks, porcelain shapes and the bowl.
Step 3 - Pre-Polish:
Repeat Step 3 with a pre-polish grit if desired - this is optional so see if your rocks need this extra step. We recommend a fine grit such as #1500 Aluminium Oxide for this stage. Paying close attention to the pre-polish stage will make a good polish much easier to achieve.
Step 4 - Polishing:
It is recommended to keep one bowl only for polishing - this prevents any possibility of grit contamination in the polish stage. If you are using the same bowl, take special care to wash it thoroughly.
Load the bowl with thoroughly clean rocks and porcelain shapes if required for filler - wet the rocks by filling and then draining the water. The thoroughly washed rocks and cylinders are placed in the polishing barrel and it is filled with water and turned upside down to drain.
Add about ¼ to ½ tablespoon of oxide polish (Cerium, Tin or 1 micron Aluminium) per kilogram of rock.
After 12 hours of tumbling, check the load. If the slurry consistency is about right (a "milky" slurry coating the rocks) and the load is tumbling properly, allow to tumble for a further 12 hours. If the polish has turned to a sticky paste, add just a few drops of water - just enough to remobilise the polish into a milky consistency. A quick spritz with a spray bottle is usually enough.
The amount of time needed for the polishing step depends upon the material being tumbled. Some rocks will polish beautifully in just 12 hours but other types of rock will require more time. Some may not polish well at all no matter what you do - experience will tell the difference.
NOTE: Some rocks will not polish well with cerium oxide - particularly the harder type rocks - in these cases, you may try aluminium or tin oxide instead.
At the end of 24 hours in the polish, take a few rocks out for thorough inspection - wash, dry and then carefully check them for polish quality. If some of the rocks are not brightly polished, try again for another 12 hours. Once a satisfactory polish has been achieved, rinse the rocks to prepare them for burnishing.
OPTIONAL Step 5 - Burnishing:
The final (optional) step is a short tumble in soapy water known as burnishing. Place the cleaned rocks back into the bowl, add about three tablespoons of water and a small amount of burnishing compound (eg. MP103), pure soap powder or flakes or even a drop or two of dishwashing liquid. Tumble the rocks for an hour or so in this soapy water. This last step removes any polish trapped in tiny spaces and just gives a final clean to the surface of the rock. One last rinse and you're done.
FINAL NOTES:
A proper slurry is needed for optimal action. If there is too little water, then the thickness of the mixture will prevent proper movement and slow the polishing/grinding action. Too much water results in too thin a slurry and slow working time significantly or the grit may settle out of the mixture altogether. If the load is too dry, it will stop rotating - add moisture with a spray bottle to get it moving correctly again. If the load is too wet, it may look like it is tumbling but grit can be washed off the rocks and start to wear the bowl. Check about every 12 hours for evaporation and add water (sparingly) if required to maintain correct slurry consistency.
Make sure you include some small rocks in the load. Adding smaller rocks helps carry the grit evenly throughout the load and improves tumbling effectiveness. You can use porcelain shapes if you dont have any suitable smaller rocks.
