How to Rock Tumble: How to Use a Rock Tumbler (4-Step Guide)

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Here's how to rock tumble: fill the barrel about half to two-thirds full of rock, add grit and water to just reach the top layer, and run it for about a week. Then clean everything and repeat with finer grit: coarse (60/90), medium (120/220), pre-polish (500 to 600) and polish. Hard stones like agate and jasper take about four to six weeks from rough to shine.

This guide walks you through each step with the fill levels, grit doses and stage times that manufacturers such as Lortone, Harbor Freight and Kingsley North publish. It covers rotary tumblers, the kind almost every beginner owns.

The 4 Stages at a Glance

Stage times come from Kingsley North's rotary instructions and Harbor Freight's manual; Lortone's manuals give 5 to 7 days per stage. Times vary with rock hardness. Our rock tumbling timeline calculator adjusts them for your stone.

What You Need

• A rotary tumbler with a rubber barrel. See our best rock tumbler picks if you don't have one yet.
• A four-stage grit kit. Our rock tumbler grit guide compares kits.
• Rough rock of similar hardness, ideally about 6.5 to 7 on the Mohs scale.
• Ceramic media or plastic pellets to top up the barrel when you're short on rock.
• A bucket, a strainer or colander, and an old toothbrush for cleanup.
• A spot in a garage, basement or laundry room, on a level surface you can wipe down.

If you're starting from scratch, a complete rock tumbler kit bundles most of this.

Step 0: Pick and Sort Your Rocks

Good results start before the barrel goes on. Tumble rocks of similar hardness together. Highland Park Lapidary recommends grouping stones by Mohs hardness so softer ones don't wear away too fast.

Beginner-friendly stones (about 6.5 to 7 on the Mohs scale): agate, jasper, quartz, petrified wood. They're hard, take a great polish and forgive mistakes.

Avoid for now: anything soft (below about 5.5, such as calcite or fluorite), crumbly, deeply cracked, or layered. Soft stones lose a lot of size in the coarse stage and bruise or pit when tumbled with harder rock.

Mix sizes. Lortone recommends assorted sizes. Small stones fill the gaps between larger ones, which improves the grinding action. Keep stones within the barrel's limit; Lortone rates its 3A for stones up to 1-1/4 in.

How to Rock Tumble: Step-by-Step Rock Tumbler Instructions

1. Load the Barrel and Run Stage 1 (Coarse Grind)

1. Fill the barrel about 1/2 to 2/3 full of rock, per Lortone. Kingsley North and Harbor Freight allow up to 3/4. Below half full, stones crash into each other instead of rolling, and they chip.
2. Add coarse grit. Use 60/90 silicon carbide at the dose for your barrel (see the chart below).
3. Add water until it just reaches the top layer of rocks. Don't overfill; Kingsley North notes that excess water inhibits tumbling.
4. Seal the lid and wipe the rim clean. Grit on the seal causes leaks. Harbor Freight's manual says to watch for leaks during the first 10 minutes.
5. Vent the barrel early. Gas can build up in the first day. Kingsley North says to open the barrel after 24 hours; Harbor Freight vents at 12 and 24 hours. After that, Lortone says to open the barrel occasionally to vent.
6. Run 7 to 10 days. Check every few days. If the slurry turns thick and pasty, add a little water.
7. Inspect. Rinse a few stones and look closely. If any still have sharp edges, pits or rough patches, repeat stage 1 with fresh grit. Kingsley North calls this the most important step, and it's where patience pays off.

2. Clean Out Between Every Stage

1. Pour the barrel contents into a strainer over a bucket, never a sink. Lortone warns against pouring rinse water down a household drain, and Kingsley North notes that slurry settles in pipes and hardens.
2. Rinse stones thoroughly, then wash the rocks and barrel parts with mild soap and water, as Lortone recommends.
3. Scrub the barrel, lid and seal with a toothbrush. Even a few leftover coarse grains will scratch your stones in later stages.
4. Cull broken stones. Anything cracked or badly chipped goes back for another coarse run or in the reject pile.
5. Dispose of slurry in the trash once it settles and dries.

Repeat this cleanup after every stage.

3. Stage 2: Medium Grind (120/220)

1. Return the stones to the barrel. If it's now below 2/3 full, top it up with ceramic media or plastic pellets.
2. Add 120/220 (or 150/220) silicon carbide and water as before.
3. Run about 7 days. Kingsley North suggests a first check at 2 to 3 days. By day 7 the stones should have an even, smooth matte finish; if not, run 2 to 3 more days.
4. Clean out thoroughly.

4. Stage 3: Pre-Polish (500 to 600)

1. Load the stones, top up with pellets if needed, and add pre-polish grit and water. Lortone uses aluminum oxide pre-polish; Kingsley North and Harbor Freight use 600 grit.
2. Run about 1 week, checking every other day.
3. Stones should have a faint sheen when dry and feel silky. Clean out very thoroughly; this is the last chance to stop contamination.

5. Stage 4: Polish

1. Load the stones with plastic pellets to reach 2/3 to 3/4 full. Kingsley North notes that pellets carry the polish and cushion the stones.
2. Add polish (aluminum oxide, cerium oxide or tin oxide) and water.
3. Run 5 to 7 days.
4. Test: rinse and dry a few stones. Kingsley North's rule is that a finished stone looks the same wet and dry. If it only shines when wet, go back to pre-polish.

6. Optional: Burnish

1. Run the clean stones with plastic pellets, water and powdered soap: about 1 tablespoon for a 3 lb barrel, per Kingsley North and Harbor Freight.
2. Run for at least 4 days. Kingsley North warns against liquid detergents, dishwasher powders and products with bleach, which can damage the barrel and ruin the polish.
3. Rinse and dry. You're done.

How Much Grit to Use

Here's Lortone's chart in level tablespoons per barrel:

As a cross-check, Rocktumbler.com recommends about 2 level tablespoons per pound of rock in a rotary tumbler.

Amazon availability: Lortone's 4-Stage Grit Pack showed as currently unavailable on Amazon.com when we checked in October 2026, and Lortone sells mainly through lapidary dealers. If you'd rather order on Amazon, the National Geographic Rock Tumbler Grit and Polish Refill Kit is a four-stage alternative sold by Amazon; National Geographic rates it for up to 20 lb of rock and says it works in any tumbler.

Common Rock Tumbling Mistakes

• Cutting the coarse stage short. Most dull, pitted results trace back here. Don't move on until every stone is rounded and free of pits.
• Underfilling the barrel. Below half full, stones bang together and chip. Top up with media.
• Carrying grit into later stages. One coarse grain can scratch a whole polish batch. Scrub the lid and seal.
• Mixing hard and soft stones. Soft stones wear away or come out pitted. Sort by Mohs hardness.
• Too much water. It cushions the load and slows grinding. Aim for the top layer of rocks.
• Pouring slurry down the drain. It settles and hardens in pipes. Use a bucket.
• Forgetting to vent. Open the barrel early in each run, especially stage 1, to release gas.
• Judging the polish wet. Always check stones dry.

If something still goes wrong, our upcoming rock tumbler troubleshooting guide covers pitting, leaks and dull shine.

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