Washed, Calcined and Agricultural Grades — Al₂Si₂O₅(OH)₄
Kaolin is the most versatile of the industrial clays: a soft, white, chemically inert aluminium silicate that fires white, extends expensive pigments, reinforces polymers and reflects sunlight. PIME supplies washed hydrous, calcined and agricultural grades through an audited supply network, with a Certificate of Analysis on every shipment.
Because Australia has almost no coated fine-paper manufacturing, the Australian demand profile differs sharply from the global one — here it is ceramics, coatings, fibreglass, refractories and horticulture that matter. We grade and price accordingly.
| Typical Specification (Washed Hydrous Grade) | Value |
|---|---|
| SiO₂ | 45 – 52% |
| Al₂O₃ | 32 – 38% |
| Fe₂O₃ | ≤ 0.9% |
| TiO₂ | ≤ 0.6% |
| CaO + MgO | ≤ 0.7% |
| K₂O + Na₂O | ≤ 1.5% |
| Loss on Ignition | 12 – 14% |
| Brightness (ISO 2469) | 80 – 88% |
| Fineness | 325 mesh · D98 < 45 µm |
| Moisture | ≤ 1.0% |
| pH (10% slurry) | 5.0 – 7.5 |
| Oil Absorption | 35 – 50 g / 100 g |
| Specific Gravity | 2.6 |
| Packaging | 25 kg bags, 1 MT bulk bags, containers |
| Supply Terms | FOB origin port · CIF destination · Ex-warehouse Australia |
Values are typical for the washed hydrous grade and are confirmed lot by lot on the Certificate of Analysis. Calcined and agricultural grades carry separate specifications — request the data sheet for the grade you need.
Low-iron, low-titanium clay for sanitaryware, tableware, wall and floor tile bodies. Retains plasticity and green strength; fires white.
Fired to metakaolin for high brightness, opacity and hardness. The standard titanium dioxide extender in decorative and industrial paints.
Controlled alumina and alkali levels for E-glass batch and alumino-silicate refractory bodies, where fluxing impurities must be limited.
Fine, high-brightness kaolin for horticultural sunburn-protection sprays, and as an inert carrier and dust in crop-input formulations.
Kaolin is not one product. Ceramic bodies need plasticity and low iron; paint needs calcined brightness and controlled oil absorption; fibreglass needs alkali limits. We supply against the grade the application actually requires, with the relevant parameters reported on the CoA.
Australia has domestic kaolin projects and no significant coated-paper industry. We position imported kaolin where it genuinely competes — specific ceramic, coating, refractory and horticultural grades — rather than claiming a market that is not there.
Kaolin almost always works in a body or formulation alongside feldspar, quartz, talc or dolomite. Sourcing them from one supplier means one CoA package, one shipment plan and consistent lot traceability across the whole recipe.
They are the same material. Kaolin is the mineralogical name, derived from Kao-Ling in China where it was first mined for porcelain; china clay is the traditional commercial name still used across the ceramics and paper trades, particularly in the United Kingdom and Australia. The active mineral in both is kaolinite, Al₂Si₂O₅(OH)₄. PIME lists the product under both names because buyers search for both.
Hydrous (washed) kaolin is the natural refined clay, retaining its chemically bound water and showing a loss on ignition of 12 to 14%. Calcined kaolin has been fired at roughly 650 to 1050°C, driving off that bound water and converting the kaolinite to metakaolin or mullite. Calcination raises brightness and opacity, increases hardness and oil absorption, and eliminates plasticity. Use hydrous grades where plasticity and green strength matter, such as ceramic bodies; use calcined grades as a high-opacity titanium dioxide extender in paints, and in polymer and cable applications where electrical properties matter.
It can extend titanium dioxide but not fully replace it. Calcined kaolin has a refractive index near 1.62 against titanium dioxide's 2.7, so it cannot match TiO₂ for hiding power on its own. What it does well is spacing: fine calcined kaolin particles hold TiO₂ particles apart, preventing the crowding that wastes opacity at high pigment loadings. In practice, formulators commonly displace 10 to 25% of TiO₂ with calcined kaolin while holding contrast ratio, which is a meaningful saving given the price gap between the two. The achievable substitution depends on your gloss level and PVC, so bench trials are essential.
Kaolin is sprayed onto orchard and vineyard canopies as a particle film, forming a white mineral barrier that reflects infrared and ultraviolet radiation while transmitting usable photosynthetic light. It lowers fruit surface temperature during peak heat and reduces sunburn incidence, with published trials reporting reductions of roughly 50 to 60% in high-temperature seasons. It is used on apples, pears, citrus, stone fruit and wine grapes, and the same film also deters some insect pests. Australian growers use registered products in this category, and interest has grown with heat-stress pressure on fruit quality. Kaolin supplied for crop application must be of appropriate grade, and any product applied to crops must be registered with the APVMA — PIME supplies the mineral raw material to formulators, not a registered crop product.
Fired whiteness in a ceramic body is governed largely by iron and titanium content in the clay fraction. Fe₂O₃ above roughly 1% produces a cream to buff fired colour rather than a white one, and TiO₂ compounds the effect by producing a yellow cast. For sanitaryware and tableware, where a bright white body is expected, low-iron washed kaolin is essential. PIME reports Fe₂O₃, TiO₂ and ISO 2469 brightness on the Certificate of Analysis for every lot so that body formulations remain stable batch to batch.
Approximately 30–45 days FOB origin port, or 50–65 days CIF to Australian east-coast ports, depending on sailing schedules. Kaolin is hygroscopic in humid transit, so we specify moisture-barrier liners for container shipments into northern Australian ports.
A current Safety Data Sheet (SDS) is supplied with every consignment and is available on request. Kaolin is handled as a nuisance and respirable dust; natural kaolin may contain low levels of crystalline quartz, and the quartz content is reported on request. Workers should follow Safe Work Australia guidance, use appropriate PPE, and implement dust-control measures in line with the Work Health and Safety Regulations.
Contact our team for grade selection, specifications and delivery options — or request an evaluation sample for your laboratory's bench testing.
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