Start with the surface treatment

Sepoz SPZ-35 is uncoated micronized calcium carbonate. SPZ-35C has a stearic-acid coating at a typical 0.9% by weight. Coating and particle size describe different properties: choosing a coated grade does not, by itself, tell you how fine the powder is.

Compare like-for-like measurements

The supplied TDS for both grades reports a typical D50 of 2.629 μm and D98 of 7.2 μm. These matching values do not mean the two materials are interchangeable in your formulation. The surface treatment is an additional variable to evaluate.

Sepi’s takeaway

Specify both the coating requirement and the particle-size distribution. A mesh number alone does not describe both.

What should you send our team?

  • Your application and resin or binder system.
  • Your current grade, target loading and the result you want to evaluate.
  • Particle-size targets, coating requirements and any moisture limit.
  • Trial quantity and delivery destination.

Compare the complete specifications for SPZ-35 and SPZ-35C. Ask for a sample and assess it in your own process before agreeing a production specification. TDS values are typical characteristics, not batch certificates or guaranteed limits.

Source: Sepoz technical data sheets, revision 01, 30 August 2026. SPZ-35 TDS (PDF) · SPZ-35C TDS (PDF)