Barrel & Grit field manual
Rock tumbler grit chart: a clean four-stage schedule
The mesh number matters, but inspection and cleanliness decide when a batch is ready to move forward.
Stage 1 — coarse shaping
Use coarse silicon carbide, commonly in the 60/90 range. Run until pits, cracks and sharp edges are gone—not merely until seven days pass.
Stage 2 — medium smoothing
A 120/220 or 150/220 abrasive removes the deep scratches left by coarse grit. Wash the barrel rim and lid separately before reloading.
Stage 3 — fine or pre-polish
Fine silicon carbide around 500 mesh prepares a uniformly smooth surface. Any stone with a fresh crack should go back, not forward.
Stage 4 — polish
A suitable aluminum oxide polish produces the final shine on compatible material. Keep polish barrels, media, scoops and brushes isolated from coarse grit.