Quick Answer

Uneven gloss on polished concrete almost always comes from uneven scratch removal in earlier grits, not from the final pad. Fix it by going back one grit, checking pad pressure on the grinder, and re-running the floor with fresh, matched sets of resin polishing pads. Run a gloss meter or a flashlight at a 15-degree angle across the floor to find the dull patches, then re-polish those zones. The goal is the same scratch depth and the same pad pressure across every square meter - not more gloss on the final step.

Why Gloss Goes Uneven

Gloss is a measure of how flat the surface is. Flatness comes from the entire grit sequence, not just the last pad.

Diagnose With Light, Not Eyes

Walk the floor at dusk or with the lights off and a bright flashlight at 15 degrees. The light reveals the scratch pattern before the gloss does. Every patch that looks dull in the flashlight is a place where an earlier grit was not fully removed.

If you have a gloss meter, target readings and record them:

• 60-degree gloss meter - 20 units variation across the floor is acceptable; 50+ units is a problem.
• Walk grid - every 5 m, take a reading. Mark low spots with tape.
• Compare to sample board - most clients approve a sample; match it.

Re-Polish the Low Zones

Once you have the dull patches marked, fix them. Do not try to burnish them brighter - that just moves the problem.

1. Drop back one grit (e.g. from 1500 to 800).
2. Run fresh pads across the whole marked zone, overlapping into the good area by 1 m.
3. Move to the next grit up - whole floor, not just the patch, to blend.
4. Repeat through 1500, then 3000 if needed.
5. Burnish the whole floor flat.

Use a spiral-segment resin pad on re-work - the spiral design cuts evenly and does not leave arc marks that confuse the final gloss.

Pad Pressure and Machine Setup

Gloss also depends on the head sitting flat on the slab. If the head tilts, one side cuts harder than the other.

• Check head level - place a straight edge on the plate; adjust link arms.
• Even weight - split weight evenly across the head, not all on one side.
• Matched pad set - pads wear at different rates; replace all three together.
• Pad temperature - let pads warm up for 30 seconds before judging gloss.
• Direction overlap - 30% overlap between passes; missing a strip leaves a dull stripe.

Frequently Asked Questions

Q: Why does my floor look glossy in the morning but dull by afternoon?

Dust and traffic. Burnish the floor once a week. If the gloss still varies, the base scratch pattern is uneven.

Q: Can I fix uneven gloss by adding more sealer?

No. Sealer smooths small variations but cannot hide a 50-unit gloss difference. Re-polish.

Q: How long does re-polishing a 200 sqm floor take?

8-12 hours: 1 hour diagnosis, 4 hours re-run through 800/1500, 2 hours 3000, 1 hour burnish, 1 hour cleanup.

Q: Should I use gloss meter readings on the sample board?

Yes - record the gloss on the approved sample and match it at the end. This prevents "I wanted more shine" arguments.

Conclusion

Uniform gloss is a flatness problem, not a final-pad problem. Diagnose with a flashlight, drop back one grit, re-run with fresh matched pads, and burnish flat. JOY TECH supplies matched resin pad sets and spiral-segment pads that leave even scratch patterns across the whole floor.