ESSwirl marks are the small circular scratches that appear in a stone surface just as it reaches a gloss. They stand out most on dark, polished stone, where any change in reflection is obvious. They are also almost entirely preventable, because they come from a handful of causes that the operator controls: the grit sequence, the cleanliness of the pads and the way the machine is run.
What swirl marks actually are
A swirl is a scratch curve left by the pad's rotation, usually from a coarse particle trapped under a finer pad or from a grit step that was skipped. In a perfect finish, each grit removes the scratch pattern of the one before, leaving nothing that can be seen in the reflection. Swirls appear when that chain is broken - coarse grit survives into a stage that cannot remove it, or the pad itself is contaminated.
The usual causes
- Skipping a grit: the most common cause. Move from coarse to fine without a step and the finer pad cannot erase the coarser scratch.
- Contaminated pads: using the same pad for two grits, or a pad that picked up grit from the floor or the sink, drags coarse particles into a fine stage.
- Polishing dry when the pad needs water: slurry that should have been flushed away stays on the pad and grinds into the surface.
- Too much speed: running the pad fast builds heat and makes it harder to control, which leaves marks.
- A rigid backer on an uneven surface: the pad tilts or bridges and cuts unevenly.
- Worn or glazed pads: a pad that has stopped cutting just rubs, spreading existing scratches around.
- Excessive pressure: forcing the pad loads it and produces heat and swirls rather than a clean cut.
Prevention, step by step
- Plan the grit sequence before starting and never skip a step, however tempting.
- Dedicate a pad to each grit - label them if you have to - and never mix.
- Rinse pads and the surface between grits so no coarse grit carries forward.
- Keep water flowing on wet work; a dry surface is a swirl generator.
- Run the machine at a controlled speed and keep it moving in overlapping passes; dwelling in one spot leaves a mark.
- Use light, steady pressure and let the diamond cut.
- Match the backer to the surface: rigid for flat, flexible for curved.
The same discipline that avoids swirls also avoids the haze and uneven gloss covered in our polishing pad troubleshooting guide.
Fixing swirls you already have
Once swirls are in the surface, polishing harder will not remove them - it can make them worse. The fix is to go back to the grit that created the scratch and work forward again, cleaning everything thoroughly first. If the swirls are fine and shallow they may respond to stepping back one or two grits; if they are deep, the surface has to be re-cut from coarser. Check pads for contamination before restarting, because using the same dirty pad will recreate the problem.
Matching pad and stone
Soft, light-coloured stones hide swirls better than dark, dense ones, but none are immune. If you polish a lot of dark stone, a wet diamond polishing pad run through a full grit sequence is the safest route to a swirl-free finish, and a final pass with a clean, fine pad brings up the gloss without dragging grit across the surface.
Safety
Wear eye protection, a dust mask or respirator and hearing protection, use water or extraction to control dust, and keep water away from electrical connections with an RCD or GFCI. Secure the workpiece, respect the tool's speed and follow the manufacturer's instructions. Clean your pads properly at the end of every job - contaminated pads are both a quality problem and a hazard when they throw grit.
Avoiding swirls in short
- Never skip a grit, and never share a pad between grits.
- Keep it wet, keep it moving, keep the pressure light.
- Match the backer to the surface.
- Fix swirls by going back a grit, not by polishing harder - browse the polishing tools range for pads and backers.
