Step 2 of the process
Medium grind
Removes the scratches left by the coarse grit and leaves a smooth, matte surface.
- Goes in the barrel
- medium grit, 150/220 silicon carbide
- Typical run, rotary
- about 7 days
Step 2 uses medium 150/220 silicon carbide (some brands label it 120/220). It does not change the shape any more. Its job is to remove the deep scratches left by the coarse grit.
Before you load it, wash everything: stones, barrel, lid and the lid seal. A few grains of coarse grit left in the barrel will keep scratching all week. Then load the same way as before, with the same amount of grit, and run for about 7 days.
The barrel will be a little emptier now, because the stones lost size in step 1. Bring it back up to the fill line with ceramic media.
Ready to move on when: The stones are smooth and evenly matte. Under a bright light there are no coarse scratches left.
Common mistakes at this stage
- Skipping the wash between steps.
- Letting the barrel drop under half full after the stones have shrunk.
Gear for this stage
Useful at every step
- How much grit to use in a rock tumblerHow much grit, rock and water for your barrel, with run times for every step.Tool
- Rock tumbling grit chart: grit size, amount and time for each stageRock tumbling grit chart for all four steps: grit size, what each step does, days per step and how to tell it is done, plus about 2 tbsp of grit per pound.Chart
- How long to tumble rocks: time for each stage and the full runHow long rock tumbling takes: about 7 days per stage and 4 to 6 weeks for a full batch, with times by rock type and the signs that a stage is finished.How-to
- How to tumble rocks: a step-by-step guide for beginnersHow to tumble rocks in a rotary tumbler: load the barrel 2/3 full, run four grit steps of about 7 days each and clean between them. 4 to 6 weeks in total.How-to