A coarse solar salt sample can look suitable while its sieve report tells a different story. For an industrial buyer, the useful question is how much material falls inside the agreed size band. This guide explains how to read individual retention, cumulative retention and passing percentages before approving a sun-dried large-grain salt shipment.
1. Define the size requirement before comparing reports
Solar describes the evaporation route; coarse describes a physical size category. Neither word specifies one universal particle distribution. Cargill's industrial salt overview, for example, lists several screened solar salt sizes. It illustrates why the size description needs a measurable definition.
Start with the intended feeder, conveyor or brine-making equipment. State screen openings in millimetres or micrometres, the required proportion within the target band, and separate limits for fines and oversize material. If a report uses mesh numbers, request the sieve designation and aperture rather than assuming every mesh system has identical openings.
Use the industrial salt product page to describe the material being requested, then agree the actual size limits for the application. A sieve report describes passage through specified openings; it does not measure an exact diameter for every irregular crystal.
2. Distinguish individual retention from cumulative retention
In a sieve stack arranged from larger to smaller openings, individual retained percentage is the mass collected on one sieve divided by the original test mass, multiplied by 100. Cumulative retained percentage adds that sieve's retained mass to all material held on larger sieves. Percentage passing equals 100 minus cumulative retention, provided the mass balance is complete.
The following hypothetical 1,000 g sample demonstrates the arithmetic. These values are neither Hailei supply specifications nor acceptance limits.
| Screen opening | Mass retained | Individual retained | Cumulative retained | Passing |
|---|---|---|---|---|
| 4.00 mm | 80 g | 8% | 8% | 92% |
| 2.00 mm | 620 g | 62% | 70% | 30% |
| 1.00 mm | 240 g | 24% | 94% | 6% |
| Collection pan | 60 g | 6% | 100% | Not applicable |
Here, material passing 4.00 mm and retained on 1.00 mm totals 62% + 24% = 86%. The same result is 92% passing the upper screen minus 6% passing the lower screen. Adding cumulative percentages would double-count material.
Cargill's processed coarse salt product sheet provides a real example of screen openings and typical retained percentages. Its product values and approvals belong to that named product and are not specifications for Hailei salt.
3. Check the sample condition and mass balance
Add individual retained masses, including the pan, and compare the total with the starting test mass. Investigate missing material or an unexplained change before calculating acceptance. Rounding can make displayed percentages differ slightly from 100%; it cannot explain a substantial recovery gap.
Record the lot, sampling locations, sample preparation, starting mass, sieve set and test procedure. Moisture and agglomerates can change how a sample behaves. Reports are not directly comparable if one laboratory dries or breaks up lumps while another tests the salt as received. Agree the treatment in advance and record any deviation.
The industrial salt technical buyer guide connects physical checks with lot traceability. Keep the sieve result linked to the sampled shipment, not just a generic product brochure.
4. Translate the report into a purchasing decision
Compare each result with the agreed limit: target-band fraction, fines and oversize. State whether the supplier's figures are guaranteed limits, typical data or results for the particular lot. A typical curve alone cannot establish shipment conformity.
Particle size also does not establish chemical purity. Review moisture, NaCl reporting basis and relevant impurities separately using the industrial salt specification checklist. Confirm equipment suitability through the agreed trial; coarse industrial solar salt is not automatically approved for every softener or resin system. For dissolving operations, the brine preparation guide provides related process context.
When requesting a coarse solar salt quotation, include the application, screen openings, percentage limits, sampling method, chemical requirements, quantity, packing and destination. Available grades and delivery terms require confirmation for the inquiry.
5. Frequently asked questions
Does 70% retained mean 70% is larger than that screen?
Only if the figure is cumulative retention. An individual retained figure excludes material already caught on larger screens. Check the column heading and test arrangement before interpreting it.
Can photographs replace a sieve report?
Photographs help communicate appearance. They do not quantify the mass fraction of fines, oversize or material within a specified band across a representative sample.
Is the pan fraction always unacceptable fines?
No. The pan contains material passing the smallest test sieve. Whether that fraction is classified as fines, and how much is acceptable, depends on the agreed lower size limit and application.