Magnifying glass held over a pile of pebbles to inspect them

Troubleshooting Your Tumbling Problems

Most tumbling problems have a simple cause and an easy fix. Find what you are seeing below, check the likely causes, and follow the fix. If you are still stuck, tell us what happened and we’ll help you sort it out.

Problems with the finish

Stones are hazy or dull after the polish

Likely causes

  • Leftover coarse grit in the barrel, the filler or the stones.
  • The coarse step ended before every pit and rough spot was gone.
  • Steps were too short, so scratches from the last grit remained.
  • The stones are porous or grainy and will never take a glassy shine.

Fix

  • Check the stones dry, under good light.
  • Scrub the barrel, lid, stones and filler, then rerun the 500 pre-polish with fresh grit and plastic pellets.
  • Run the final polish again, ideally in a separate polish barrel.
  • Finish with a short burnishing run. More detail: keeping that underwater look.

Stones look great wet but dull when dry

Likely causes

  • Water fills fine scratches, so wet stones always look polished.
  • A step was skipped or cut short.

Fix

  • Judge every step on dry stones only.
  • Go back to the step where the surface still looks scratched, and work forward again.
  • See how to tell when a step is done.

Scratches appear in the pre-polish or polish

Likely causes

  • A coarse grain carried over on the stones, the filler or the barrel seal.
  • A cracked stone shedding sharp pieces.

Fix

  • Clean everything thoroughly and pull any cracked stones.
  • Use separate plastic pellets for the polish steps.
  • Rerun the step before the one where scratches appeared.

Problems with the stones

Stones are chipped, bruised or broken

Likely causes

  • The barrel is too empty, so stones crash instead of rolling.
  • No cushioning in the finer steps.
  • Hard and soft stones mixed in one load.
  • Brittle stones such as obsidian, or cracks that were already there.

Fix

  • Fill the barrel two-thirds to three-quarters full, topped up with filler.
  • Add plastic pellets from the pre-polish on, or from the start for brittle stones.
  • Pull broken stones, then go back a step to grind out chips and bruises.
  • Full guide: chipped, bruised or broken stones.

Stones are still rough or pitted after the coarse step

Likely causes

  • The coarse step needs more time; one week is often not enough.
  • The grit wore out, or too little was used.
  • The rock needs a coarser start.

Fix

Stones are wearing away or getting too small

Likely causes

  • Soft stones tumbled with harder ones, or run too long.
  • Too many coarse steps.

Fix

  • Check the hardness chart and tumble soft stones on their own.
  • Shorten each step and check every two or three days.
  • Start already-smooth stones at 120/220 instead of coarse.

Stones came out with a frosted or uneven surface

Likely causes

  • Mixed hardness within one stone, such as softer veins or inclusions.
  • Granular rocks like granite or quartzite.

Fix

  • This is often the nature of the stone and not a fault.
  • A longer pre-polish and a finer polish can improve it.

Barrel and machine problems

The barrel is leaking

Likely causes

  • Grit on the rim or seal stops the lid from sealing.
  • The lid is worn, cracked or not seated evenly.

Fix

  • Wipe the rim and lid dry and clean before closing.
  • Check the lid and gasket, and replace them if they are cracked or stretched.

The lid is swollen or the barrel builds pressure

Likely causes

  • Some stones and reactions release gas as they grind, especially in the coarse step.

Fix

  • Open the barrel every day or two during the coarse step to let it vent.
  • Point the lid away from your face when opening it.

The barrel stops turning or slips on the rollers

Likely causes

  • The load is heavier than the motor is rated for.
  • A stretched or cracked drive belt.
  • Grit or slurry on the rollers.

Fix

  • Stay within the rated weight.
  • Clean the rollers and replace a worn belt.
  • Set the tumbler on a level surface.

The slurry is too thick, or too thin and watery

Likely causes

  • Too much grit or too little water makes a thick, sticky slurry; too much water makes a thin one that cushions poorly.

Fix

  • Keep the water just below the top layer of stones.
  • Measure the grit for the weight of the load.
  • If the slurry is very thick at the end of a week, that is normal: the grit has done its job.

The tumbler is too noisy

Likely causes

  • A hard plastic barrel, or a barrel that is not full enough.

Fix

  • Fill the barrel properly and add filler.
  • Rubber barrels run quieter. Put the tumbler in a garage or basement on a rubber mat.

Vibratory tumbler problems

The load stops moving or moves slowly

Likely causes

  • The slurry has thickened or dried out.
  • The bowl is overfilled or underfilled.

Fix

  • Add a little water two or three times a day as the slurry thickens.
  • Fill the bowl to its rated load. See our vibratory guide.

Grit settles and wears the bowl

Likely causes

  • Too much water lets grit settle out.

Fix

  • Pour off standing water and keep a creamy slurry.

Steel shot and metal problems

Metal is still dull or tarnished

Likely causes

  • Not enough soap or burnishing compound, or a run that is too short.
  • Old, dull or dirty shot.

Fix

  • Run 1 to 4 hours with enough water to cover the load and a few drops of soap.
  • Rinse the shot after every batch until the water runs clear.
  • See our steel shot guide.

Steel shot is discolored or rusty

Likely causes

  • Shot stored wet in dirty water.

Fix

  • Store it dry, or covered in clean water.
  • Our shot is 304 stainless steel. Light discoloration usually cleans up with a soapy run.

Pins are stuck inside brass casings

Likely causes

  • Stainless pins can lodge inside cases. They are not magnetic, so a magnet will not pull them out.

Fix

Still stuck?

Send us your tumbler model, what you are tumbling, which step you are on and what you are seeing, and a photo if you can. Contact Rockridge and we’ll help you work out the fix.

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