Concrete densifier is what gives polished concrete its long-lasting hardness, improved reflectivity, and abrasion resistance. Applied at the right time during the polishing process — usually after 200 grit — densifier chemically reacts with the slab, hardening it from within. Done correctly, it ensures deeper polish, stronger stain resistance, and longer pad life. Done wrong, and you can end up with streaks, surface crusting, or missed penetration. Here’s how to get it right every time.
Densifier should be applied after you’ve honed the slab to at least 200 grit. The surface should be flat, clean, and free from deep scratches or slurry. Don’t apply densifier before this — it’ll react unevenly, seal over cuts, or block polishing later. This is the point when pores are open enough to absorb it, but smooth enough for even reaction.
Most professional polishers use lithium or sodium silicate densifiers. Lithium works well on tighter slabs and gives a clearer finish. Sodium densifiers are great for dust control and cost-effectiveness but may require more effort to clean up. Avoid overusing — apply once, evenly, and allow proper cure. Some densifiers include dye-lock or stain guard properties, which may affect your colour timing.
Vacuum or auto-scrub the slab to remove all dust, slurry, or contaminants. A dirty surface will block densifier absorption. If you’re wet honing, allow the floor to dry for at least 1–2 hours before application. Test for dampness with your palm or tape — densifier must be applied to a dry, open slab to react correctly.
Use a low-pressure pump sprayer and apply the densifier in a consistent mist pattern. Work in 2–3 metre sections and keep the surface wet for 10–15 minutes. You’re not trying to soak the slab — just saturate it until rejection (when it stops absorbing). Don’t let it puddle, and avoid applying in direct sun or heat. If the floor is porous, a second light coat may be needed in high-traffic zones.
After spraying, use a clean microfiber applicator to evenly spread and distribute the densifier. This helps avoid streaking, pooling, or dry patches. Work in overlapping figure-eight or circular motions. Keep moving until the slab has absorbed what it can — then stop. More is not better here. Excess will crystallise or leave a haze when it dries.
Allow the slab to fully absorb and chemically react with the densifier. This can take 30–60 minutes depending on conditions. Do not rinse or scrub during this period. If a haze forms, lightly buff it off later — but don’t disturb the reaction process too early. Once dry to the touch, you can resume polishing.
Some densifiers leave behind a faint white haze or streaks. If this happens, use a high-speed burnisher, white pad, or auto-scrubber to remove excess before going up to your next grit. Don’t move on until the floor is clean and residue-free. Any leftover product can interfere with dye, sealer, or polishing pad performance.
After the densifier has cured, continue with 400, 800, and higher resin grit passes. You should notice improved clarity, tighter surface feel, and better reflectivity. Densification strengthens the slab and improves pad lifespan — so each pass is more efficient. If you plan to colour the floor, apply dye after densifier but before your final polishing grits.
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