Barrel & Grit field manual
How much grit to use in a rock tumbler
The correct rock tumbler grit amount depends on barrel size, abrasive stage and manufacturer instructions—not on filling the barrel with powder.
Use the product instructions first
Grit concentration varies by abrasive and formulation. Follow the tumbler or grit supplier’s measurement for each pound of loaded rock rather than assuming every scoop is equal.
More grit is not automatically faster
A barrel can only use abrasive while it is moving correctly. Excess grit may remain in the slurry without improving the surface and makes cleaning more wasteful.
Recharge coarse grit when needed
Coarse silicon carbide breaks down during the run. If a difficult batch still has pits after a week, clean it, inspect the stones and reload with a fresh measured charge.
Keep notes for repeatable batches
Record rock weight, media, water level, grit amount and run time. A simple notebook turns the next batch from guesswork into a controlled adjustment.