Calcium carbonate extenders and titanium dioxide opacity — the filler and pigment package that controls hiding, film build, and cost in architectural and industrial coatings.
Mineral fillers and extenders are the particulate solids that give a coating opacity, film build, and lower cost per gallon. They split into two roles: an opacifying pigment — titanium dioxide, which scatters light and does the hiding — and extender pigments such as calcium carbonate that occupy volume at a fraction of the price. A workable formula uses both. Specify titanium dioxide for hiding power, then carry the pigment volume with extenders sized to the finish you need.
Titanium dioxide is usually the most expensive raw material in a paint formula, so extender and spacing strategy drives cost more than any other pigment decision. Calcium carbonate is the standard extender: it fills volume, supports the film, and lets a formulator hold hiding while trimming titanium dioxide content. The honest trade-off is opacity. Replace too much titanium dioxide with low-refractive-index extender and hiding falls off, so balance the swap against the contrast ratio your spec requires.
Calcium carbonate carries most extender duty across primers, fillers, and architectural paints, while zinc oxide serves as a multifunctional white pigment where formulators want added function alongside color. Filler loading itself is the second trade-off. Raising the pigment volume concentration cuts material cost, but above the critical PVC a film can lose gloss, scrub resistance, and durability. Set loading against the gloss and exposure target for the finish rather than cost alone, and confirm any regulatory status for your market.
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