Quick Answer

Start polishing with a 200-grit resin pad after the metal bond phase reaches 200 grit. If your metal phase ends at 120 grit, use 150-grit resin to bridge the gap; never jump from metal 80 straight to resin 400. The transition step is what prevents visible scratches in the final gloss.

The Grinding-to-Polishing Transition

Metal bond segments cut fast and leave coarse scratches; resin pads refine them. The changeover works when the first resin grit matches or slightly refines the last metal grit. The standard transition is metal 200 to resin 200: the resin step continues removing the metal scratches at the same size, then starts refining. If the metal phase ends coarser, add an intermediate resin grit (150 or 100) before going finer.

Why 200 Grit Is the Safe Default

Starting at 200 resin gives the resin pads enough work to remove the metal scratches completely while still cutting quickly. Starting finer, like 400, forces the 400 pad to remove deep 200-grit scratches; it will glaze, load, and leave marks. Starting coarser than the metal phase wastes time. The 200-to-200 handoff is the balance point used on most polished floors.

Adjusting for Floor Condition

On soft, young concrete, start at 150 or 100 resin because soft concrete leaves deeper scratches from the metal bond. On very hard, dense concrete, metal 200 can almost merge into resin 400, but most contractors still run a 200 resin step for consistency. On repaired or patched floors, match the transition to the coarsest patch area so the whole floor progresses together.

Confirming the Handoff Worked

After the first resin pass, inspect the floor under raking light. You should see a uniform, fine scratch pattern with no leftover coarse lines. If coarse scratches remain, re-run the metal phase at 200, then repeat the resin 200 pass. Moving forward before the pattern is uniform guarantees swirls at the gloss stage.

Frequently Asked Questions

Q: What if my metal bond only goes to 120 grit?

A> Bridge with a 150 resin pad before 200, or use a metal 200 pass if you have one. The rule is: the first resin grit must match or refine the last metal grit.

Q: Can I start polishing at 400 grit resin?

A> Only if the metal phase ended at 200 and the floor is very clean. Even then, a 200 resin step improves the result. Skipping it risks visible scratches.

Q: Is starting grit different for wet polishing?

A> The transition rule is the same wet or dry, but wet resin pads cut differently; keep the same first-grit rule and adjust feed, not grit choice.

Conclusion

The polishing phase starts where grinding ends. Match the first resin grit to the final metal grit, defaulting to 200-to-200, and verify the pattern before moving finer. That handoff is what separates a mirror finish from a floor full of swirls.