FAQ

D50 is the median of the cumulative particle size distribution, usually measured by laser diffraction. Different instruments and different dispersion conditions can produce quite different numbers. The main variables are the dispersant medium (water or organic solvent), the type and dose of dispersing agent, ultrasonic power and duration, and the optical model settings. For the same powder, changing the ultrasonic time alone can shift D50 by 10-20%. That means D50 figures from different suppliers are not directly comparable unless the test conditions match. A more reliable approach is to review the full distribution curve and ask for the test method. Our COA states the test conditions so customers can verify.

Three things: a stable raw material source, fixed process parameters, and per-batch testing before shipment. Powder production is most exposed to changes in deposit or supplier; once the impurity profile shifts, no amount of process discipline compensates. On the process side, classification accuracy and coating level are the critical parameters because they determine size distribution and dispersibility. These are fixed in the work standard, so a new batch does not mean new parameters. On testing, every batch is checked for particle size distribution, whiteness or hue, oil absorption and moisture, with coating level measured where relevant. Customer-specific requirements can be added to the routine test list by agreement.

There are two types, soft and hard agglomerates, and they require completely different responses. Soft agglomerates are held by van der Waals forces and static and can be broken by dispersion. Hard agglomerates involve chemical bonds or sintered necks and cannot be redispersed once formed. Nanopowders are most prone to hard agglomeration because of high surface area and surface energy. Prevention sits in drying and storage: moderate drying temperature, avoiding repeated moisture uptake and re-drying, and sealed moisture-barrier packaging. On the user side, soft agglomerates usually mean the dispersion step is insufficient. Check the tip speed of high-shear dispersion, the dispersion time, and whether an appropriate dispersant is used. Frequently the powder is fine and the dispersion energy is not.

Cleanliness control for powder production differs from liquids: powders do not readily support microbial growth, so dust control and cross-contamination prevention are the focus. Key control points include dust collection in production areas, dedicated equipment and containers to prevent cross-contact between different powders, and cleanliness management in the packaging area. For cosmetic-grade powders we control temperature, humidity and cleanliness in the production environment and validate packaging material cleanliness. If you require a specific cleanliness class, for instance for sterile or high-microbial-control applications, raise it at the order stage so we can assess process feasibility before confirming.

Yes. Retention samples are kept for a defined period after each batch ships, with the duration depending on product type and customer agreement. Custom grades are retained longer because they correspond to a specific formula and process parameter set. Retention samples serve more than complaint handling. They enable batch-to-batch comparison: when a customer reports that this batch behaves differently, a parallel test against the retention sample quickly shows whether the product changed or the conditions did. If you keep your own samples for long-term stability observation, store them in the same packaging and conditions as the delivered goods and record the opening date, so storage differences do not create false conclusions.

Step one is always to freeze the information: keep the physical sample from the affected batch, record the use conditions, and establish how the anomaly can be reproduced. Without those three, any conclusion is guesswork. Then run a two-way comparison: test the affected batch in parallel with the retention sample to confirm whether a real difference exists, and check whether use conditions changed (formula, process, equipment, storage). In practice a meaningful share of issues trace back to a change on the user side rather than the product. If the product is confirmed at fault, we trace the raw materials, process parameters and test records for that batch, provide a root cause analysis and a corrective plan, and for batch-wide issues review inventory and shipped lots at the same time.