About High Whiteness Ball Clay
High whiteness ball clay is selected for low iron and titanium oxide content, the two impurities that most affect fired colour. After firing, it produces a white to off-white body. That allows tile makers to achieve bright, clean colours in full-body and double-charge vitrified tiles, and can help reduce the amount of zircon or other opacifiers needed in white engobes.
Premium tile bodies are pressed from spray-dried powder, so the clay must do two jobs at once. It has to provide enough plasticity and green strength for the pressed tile to survive the press, dryer and glaze line, and it must fire white without adding specks or a grey or yellow cast. This grade balances those needs. It is typically used together with more plastic standard clays and white-firing kaolins, with the proportions set by the whiteness and strength the body requires.
Obsidian Minerals measures fired whiteness on test pieces fired under controlled conditions, together with chemistry, residue and loss on ignition. Lots are released against these results so that fired colour stays stable between deliveries, which is critical for shade matching across production batches. Samples for body and glaze trials are available on request, and fired test results can be shared alongside them.
Typical specifications
| Parameter | Typical Value | Test Method |
|---|---|---|
| Fe₂O₃ | ≤ 0.9 % | XRF (internal method) |
| TiO₂ | ≤ 1.0 % | XRF (internal method) |
| Al₂O₃ | 28–34 % | XRF (internal method) |
| SiO₂ | 48–56 % | XRF (internal method) |
| Fired whiteness (1,200 °C) | ≥ 80 % | Internal method |
| Dry modulus of rupture | ≥ 2.0 MPa | ASTM C689 |
| Residue on 45 µm (325 mesh) | ≤ 1.5 % | ASTM C325 |
| Loss on ignition | 9–13 % | Internal method (1,000 °C) |
Typical values for guidance. Guaranteed limits, including fired whiteness, are stated on the Technical Data Sheet and batch CoA.
Key features & benefits
Low iron and titanium
Typical Fe₂O₃ of 0.9 % or less and TiO₂ of 1.0 % or less keep high whiteness ball clay from tinting the body grey, yellow or pink during firing.
Clean fired colour
Fired whiteness of 80 % or more on test pieces at 1,200 °C supports bright full-body and double-charge tiles and gives a neutral base for stains and pigments.
Supports leaner engobes
A whiter body can allow tile makers to reduce the thickness or zircon content of white engobes, subject to trials with their own body, glaze line and kiln profile.
Green strength for pressing
The clay keeps enough plasticity and dry strength for spray-dried bodies to press cleanly and pass through dryers and glaze lines with low breakage and edge damage.
Controlled coarse residue
Residue on 45 µm typically at or below 1.5 % reduces dark specks and surface defects, which are especially visible on polished and light-coloured porcelain tiles.
Applications
Porcelain and vitrified tiles
A white-firing plastic component in glazed porcelain and vitrified tile bodies, contributing strength in the green state and a clean, consistent white body after firing.
Double-charge and full-body tiles
Used where the body itself is visible or carries the colour, so low iron and titanium help stains develop true, bright shades throughout the tile.
White engobes and glazes
A suspending and bonding clay in white engobes and glazes, where low colouring oxides support a bright interlayer between the tile body and the decorative glaze.
Fine tableware and porcelain bodies
Suited to porcelain and fine tableware bodies where the clay must add plasticity and dry strength without compromising the whiteness or translucency of the fired ware.
Usage & handling
- Porcelain tile bodies often contain about 30–40 % clay in total; the share of this grade is set by the target fired colour and strength.
- Wet grind with the body batch in ball mills and check slip residue before spray drying.
- Keep iron-bearing clays separate in storage and conveying, as small amounts of contamination can affect fired colour.
- Store in a dry, covered area and keep lots separate for traceability.
Packaging & supply
- 25 kg and 50 kg bags for dry powder
- 1 MT and 1.2 MT jumbo bags for tile plants
- Batch CoA with fired whiteness reported for each lot
Frequently asked questions
What makes a ball clay high whiteness?
Fired colour in ball clay is mainly controlled by iron oxide and titanium oxide. A high whiteness clay is selected from seams where both are low, and where coloured mineral impurities are scarce. Organic matter burns out during firing, so a clay that looks grey or dark in the raw state can still fire white.
How is fired whiteness measured?
Test pieces are formed from the clay, dried and fired under controlled conditions, typically at 1,200 °C, and their reflectance is then measured with a colour or whiteness meter. The value is reported as a percentage. Because firing temperature and atmosphere affect colour, customers should confirm results in their own kiln during trials.
Can this grade reduce zircon use in tile engobes?
A whiter-firing body needs less covering by the engobe, so many tile makers find they can use a thinner engobe layer or a lower zircon content when moving to a high whiteness clay. The achievable saving depends on the body, the glaze and the kiln, so it should be established through production trials.
Is the high whiteness grade as plastic as the sanitaryware grade?
It is usually somewhat less plastic and has lower dry strength than the high plasticity grade, because white-firing clays tend to be coarser and lower in fine organic matter. For pressed tile bodies that is rarely a limitation. Where more strength is needed, it can be blended with a more plastic clay.
Which tile types use high whiteness ball clay?
It is used in glazed porcelain tiles, double-charge and full-body vitrified tiles, polished porcelain slabs and premium wall tiles. It is particularly valuable wherever the tile body is visible at the edge or surface, or where a white body reduces the need for a heavy engobe beneath the glaze.