Part of the process
Loading the barrel
Fill the barrel between half and three quarters full with a mix of sizes, add about two level tablespoons of grit per pound of rock, and bring the water to just below the top layer.
A barrel tumbles properly only when it is between half and three quarters full; about two thirds is the usual target. Emptier than half and the stones are thrown against each other and chip. Fuller than three quarters and they cannot fall, so nothing grinds.
Grit is measured against the weight of rock: about 2 level tablespoons per pound in a rotary tumbler, the same in every grit step. Water goes in last, up to just below the top layer of stones. The grit calculator does the arithmetic for your barrel.
If you do not have enough rock to reach the fill line, top the load up with ceramic media. Plastic pellets do a different job: they cushion fragile stones. Count either one as rock when you measure the grit.
Common mistakes at this stage
- Running a barrel that is under half full.
- Covering the rocks with water, which floats the grit away from them.
- Reusing plastic pellets from a coarser step in a finer one.
Notes for this stage
- Rock tumbler grit substitutes: what works and what failsSand, aquarium gravel, crushed glass, baking soda and no grit at all, each with a verdict. Only silicon carbide (Mohs 9 to 9.5) cuts quartz-hard rocks.Explainer
- Ceramic media vs plastic pellets in rock tumbling: when to use eachCeramic media fills the barrel and helps the grind. Plastic pellets cushion fragile stones. A table by step and tumbler type shows which to add and how much.Comparison
- Can you reuse rock tumbling grit, slurry or media?Used silicon carbide grit is spent after a 7-day run and cannot be reused. See what can be: polish slurry, ceramic media and plastic pellets, with rules.Explainer
Gear for this stage
- Best plastic pellets for rock tumbling and when to use themFive plastic pellet options for rock tumbling compared by listing: pack weight, plastic type and packaging, plus why each grit step needs its own batch.Gear guide
- Best ceramic media for rock tumbling: sizes and how much to buySeven packs of ceramic media for rock tumbling compared by listing: shape, piece size, pack weight from 1 lb to 8 lb, and the material stated.Gear guide
- Best grit refills for a National Geographic rock tumblerSeven grit refills for National Geographic rock tumblers compared by listing: grit format, stated coverage and extras. Independent site, not affiliated.Gear guide
- Best rock tumbler grit kits for a full 4-stage runSeven 4-step rock tumbler grit kits compared by listing: grade and weight of each step, total weight, stated coverage, container and included media.Gear guide