Caustic Soda Pearls — Frequently Asked Questions

A narrow size range, here 0.4–0.6 mm, is what lets pearls flow freely through screw and vibratory feeders and weigh accurately. It also means each pearl dissolves at a similar rate, so the solution strength settles quickly. In dry-blended powders such as dishwasher products, pearls close in size to the other ingredients are less likely to separate during filling and transport. If your equipment has a size limit, state it in the enquiry.

The total heat per kilogram of NaOH is the same, roughly 1.1 MJ, but pearls dissolve faster, so the heat arrives faster. In a small vessel that can take the liquid towards boiling quickly. Add pearls gradually to cold water with stirring, never water to the pearls, allow the solution to cool between additions, and use a vessel rated for the temperature.

Usually yes, because both forms carry the same NaOH content and a producer normally applies one specification to both. Recalculate the addition from the NaOH assay on the certificate of analysis, then review your addition procedure because pearls dissolve and release heat faster. If a customer specification or your quality system names the physical form, requalify before switching.

Pearls stay free-flowing only while they are dry. Once a bag is opened or damaged, the pearls absorb moisture from the air, their surfaces become sticky and they bridge in hoppers or fuse into lumps. The absorbed carbon dioxide also turns some NaOH into carbonate. Store sealed bags off the floor in a dry, covered area, reseal part-used bags at once, and handle caked material with full protective equipment.

Yes. Soap makers often prefer pearls because they weigh accurately and give off less dust than flakes. Work out the amount from the saponification value of each oil and the NaOH assay on the certificate of analysis, since a 99% product is not pure NaOH. Technical grade suits industrial and household soaps; for cosmetic products, check the grade against your safety assessor's requirements.

Ask for the product specification, a certificate of analysis for the batch to be shipped and a safety data sheet in the language required at destination. For sea freight, the carrier also needs a dangerous goods declaration showing UN1823, Class 8, packing group II. For imports into the EU or Great Britain, ask for confirmation of which REACH or UK REACH registration covers the import and your use.