Quartz in Ceramics and Glaze: Body Stability, Whiteness and Strength
Quartz is one of the fundamental raw materials of the ceramic and porcelain body: it gives the body dimensional stability and strength, and the glaze hardness and gloss. We explain the role of quartz in ceramics, why iron matters for whiteness, and how to choose the grain size.
Quartz, together with clay and feldspar, is one of the three fundamental raw materials of the ceramic and porcelain body. It gives the body dimensional stability and fired strength, while in glaze recipes it is the SiO₂ source that provides hardness and gloss. High purity and low iron are decisive for both a white body and a clean glaze colour. In this article we explain the role of quartz in the ceramic body and in the glaze, why iron is critical for whiteness, and how the right grain size is chosen.
The Role of Quartz in the Ceramic Body
In a ceramic body, clay provides the plasticity and feldspar provides the melting, while quartz acts as the non-plastic skeleton component:
- Dimensional stability: During drying and firing, quartz limits excessive shrinkage of the body and reduces the risk of warping and cracking.
- Fired strength: It gives the body mechanical strength and preserves the skeletal structure.
- Thermal compatibility: The thermal expansion of quartz is used to tune the compatibility between glaze and body; this helps prevent defects such as glaze crazing.
- Whiteness: A low iron content supports the light, clean tone desired in porcelain and white ceramics.
The Role of Quartz in the Glaze
A glaze is essentially a thin glass layer on the body, and quartz is the main SiO₂ (glass former) source of this glass:
- Hardness and scratch resistance: High SiO₂ gives the glaze a surface hardness approaching Mohs 7.
- Gloss and transparency: Pure quartz gives the glaze a clear, glossy surface.
- Chemical durability: The glaze surface gains resistance to acids, alkalis and cleaning chemicals.
Why Low-Iron, Fine Quartz?
Two properties of quartz stand out in ceramics: low iron and fineness. Iron (Fe₂O₃) causes undesirable yellow-brown tones in both the body and the glaze, which is why low-iron quartz is essential in white and porcelain products. Fineness, in turn, governs the reaction rate: micronised quartz (< 45 µm) delivers a more homogeneous body and glaze and a more complete firing reaction. For coarser fractions, granular quartz can also be supplied as required. For application details, see our ceramics application page.
Technical Specifications
The key values of the micronised quartz used in ceramic and glaze applications:
| Property | Value |
|---|---|
| SiO₂ purity | ≈ 99.8% |
| Iron (Fe₂O₃) | ≈ 0.013% |
| Hardness | Mohs 7 |
| Density | 2.65 g/cm³ |
| Grain size | < 45 µm (micronised) |
| Colour | high whiteness (low iron) |
Low iron and high SiO₂ purity are the two most important parameters for a white body and a clean glaze colour. The values are typical batch figures; a current batch analysis report is provided with every shipment.
Why Silis Kum?
For ceramic and porcelain manufacturers, our micronised quartz is ground under controlled conditions at our own facilities in the Thrace region and classified with a low-iron target. Every batch is analysed in our own laboratory, and a batch report is provided with the shipment. To determine together the quartz best suited to your body or glaze recipe, and for a free sample, get in touch with us.