Calcined Talcum Powder

If raw talc is giving your glaze bubbles, pinholes, or an uneven fired surface, calcined talcum powdwe GP-31 is the grade to look at first.

It has already been calcined. Less gas is left for the glaze to deal with in the kiln. This is especially useful in thick glaze, glossy glaze, or any formula where a clean surface matters.

The 200 mesh powder also mixes more easily into a ceramic glaze. It gives you a direct MgO and SiO₂ source without adding a coarse material that still needs heavy grinding.

For body formulas, the choice may be different. GP-31 granules can be ground with the body materials, while GP-32 raw talc powder is usually considered when magnesium input or low-expansion body development is the main target.

Do not choose only by the word "talc."Choose by where it will be used.Glaze surface problem? Start with GP-31 calcined talcum powder

Body structure or cordierite direction? Compare the granular and raw talc grades first.

One more point: talc dosage matters. A small addition may support a clean or soft glaze surface. Too much may push the glaze toward crystallization, matte texture, or a dry finish.

The numbers tell you two useful things.

First, GP-31 gives the formula a strong MgO and SiO input. Second, the Fe2O3 level is only about 0.06%. That is why this grade is a better fit for white or light-colored glaze systems where a grey fired tone would be a problem.

For glaze work, choose the 200 mesh powder.
For body milling or further grinding, the granular form may be more practical.

Two More Ways to Use calcined talcum powder

In some glaze formulas, GP-31 can help the surface move toward a softer white or semi-opaque look. It is not a zircon opacifier. The final effect comes from the MgO–SiO2 balance and the cooling curve.

Talc is also used in cordierite, low-expansion, and electrical porcelain bodies. For these body systems, GP-31 granules or GP-32 raw talc may be more practical than the 200 mesh glaze powder.

For ceramic glaze, calcination matters.

Raw talc may still release water in the kiln. GP-31 has already passed that stage, so it is a better fit for glaze systems that are sensitive to bubbles, pinholes, or an unstable surface.

Purity matters too. GP-31 contains about 0.06% Fe₂O₃, with fired whiteness around 93.4. It gives the glaze a clean MgO source without adding an obvious grey tone.

But dosage still needs care.In a glossy glaze, too much calcined talc powder may bring more crystallization during cooling. The surface can move from soft gloss toward matte, rough, or dry.

China has mature talc mining, calcination, and powder processing. For you, however, the real value is not the country name. It is whether the MgO level, iron content, whiteness, and particle size stay consistent from one shipment to the next.

Let the Fired Surface Decide.

Take one fired glaze sample.Mark the firing temperature, the talc you are using now, and the surface you want - gloss, soft matte, or semi-opaque.

Add a clear photo of the defect or fired effect.From there, we can judge whether GP-31 powder, GP-31 granules, or GP-32 raw talc is the better grade for your next trial.

Send it over when you are ready. We would be glad to take a look.

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