A mineral-powder listing may state D50, D97, an average particle size, a mesh designation or several of these together. They describe different pieces of particle information. Reading them as interchangeable numbers can conceal the very difference that a buyer needs to investigate.
The practical aim is to understand what was measured, on which basis, by which method and for which grade. This guide follows a buyer reviewing two specification sheets, from the first size statement to a documented question for the supplier. It provides no universal conversion table between mesh and distribution percentiles.
Begin with the complete reported expression
Copy the whole particle statement into your comparison, including the symbol, number, unit, range and any accompanying method. Do not reduce D50 8 micrometres to size 8 or replace a mesh range with a guessed average. Retaining the original expression helps prevent mistakes when the enquiry moves between purchasing, the laboratory and the supplier.
Also record the source: listing, TDS, COA or a separate laboratory report. A grade description and a batch result do not necessarily have the same status. Ask whether the figure is a typical characteristic, a specification limit or a measurement of the particular sample under discussion.
If the statement lacks a unit or method, mark it as incomplete. Do not repair the source silently by adding a plausible unit. A targeted clarification is preferable to a spreadsheet cell that looks complete but rests on an assumption.
D50 and D97 are distribution points
D50 is a median particle-size value on a specified cumulative distribution. D97 similarly identifies the size below which 97 percent of that distribution falls. The distribution basis matters: volume, number and other bases describe different weightings. A median is also distinct from a calculated mean. See HORIBA's distribution statistics explanation for the distinction.
For a purchasing comparison, write the basis beside the percentile. If it is not stated, ask. Do not assume that two values with the same symbol were obtained under comparable conditions, and do not relabel a stated average as D50 merely because a median would be convenient for the comparison.
Ask which additional distribution information is relevant to your application. Your technical team may need the full curve or other points to understand a candidate grade. The appropriate request depends on the decision being made; one number should not be expanded into an imagined complete particle distribution.
Mesh requires a separate reading question
A mesh designation belongs to a sieve-related description and needs the applicable standard and reporting context. Ask what the stated designation means for the offered grade: which sieve definition applies, what passage or retention criterion is intended and whether the listing describes a product range or a particular result.
Keep this question separate from the percentile question. A mesh statement does not, by itself, give the material's D50 or D97. Nor does a D50 result tell you every sieve result. Where a comparison genuinely requires both, request the relevant measurements rather than inferring one from the other.
Catalogue ranges deserve particular care. A broad mesh range may identify several available designations or a selection range. Ask which option is being proposed for the enquiry and which specification applies to its sample. Do not treat the full range as a guarantee that every particle lies between two implied sizes.
The method is part of the result
Record the measurement technique and the method information needed to interpret the result. For a laser-diffraction report, ask for the distribution basis and the sample-preparation and dispersion conditions relevant to comparison. For a sieve-related report, request the standard, procedure and reported passage or retention information.
Different preparation conditions can make a comparison difficult to interpret. Ask the laboratory which details need to match and which differences can be assessed. The buyer should not create a universal correction factor between reports simply because both contain a particle-size number.
Keep instrument settings and method revisions with the technical record where they are relevant. HORIBA's guidance on setting size specifications links specification choice to the technique and distribution basis. For the buyer, the useful action is to agree a comparable reporting basis before ranking grades.
Read shape and dispersion as additional information
A particle-size report does not answer every morphology question. If a listing describes whiskers, plate-like particles or another shape, keep that description separate and ask what evidence is available for the shape characteristic needed by your process. Do not infer an aspect ratio from a mesh label.
Likewise, distinguish the offered powder from the way the laboratory prepared it for measurement. If agglomeration or dispersion behaviour is relevant to your application, ask your technical team which incoming and application tests will investigate it. A reported size statistic should not be turned into a universal dispersion-performance promise.
The goal is a record in which each observation answers its own question: particle distribution, morphology, treatment and application response. Combining them into one adjective such as ultrafine can make communication shorter while making the actual requirement less clear.
A comparison sheet that preserves the differences
Use rows for the exact reported statistics and columns for the two candidate grades. Add columns for method, unit, distribution basis, document revision and unresolved questions. If a row cannot be compared, say so. This makes the information gap visible without declaring either material unsuitable on evidence that is not yet available.
| Field | What to preserve | Question if missing |
|---|---|---|
| Grade identity | Actual model and proposed form | Which grade does the sample represent? |
| D50 / D97 | Value, unit and distribution basis | Which method and preparation were used? |
| Mesh | Original designation and reporting context | Which sieve standard and criterion apply? |
| Average size | The original statistic name | How is the average defined? |
| Status | Typical value, limit or batch result | What is the accepted purchasing requirement? |
Do not insert invented example values into a purchasing record. The table above is a structure, not a specification. Populate it with the actual grade information and retain the source documents so another reviewer can check how the comparison was made.
Two common review situations
One sheet gives mesh and the other gives D50
The initial conclusion is that the sheets report different information. Ask which measurement would support your application decision and whether comparable data can be supplied for both candidates. If not, define an appropriate sample evaluation. Avoid presenting a guessed conversion as a measured property of either grade.
Both sheets give D50 but the methods are unclear
Request the distribution basis, technique and preparation details before ranking the numbers. Ask whether the figures are typical grade descriptors or sample results. If the technical team accepts a comparison despite method differences, record that judgement and its limits rather than removing the method fields.
In both situations, the useful next step is a specific request. The question could be: please provide the particle distribution report for the proposed grade, identify its basis and method, and clarify whether the values apply to this sample or are typical grade data.
Connect the particle requirement to an acceptance decision
A particle specification should help answer a real material-selection question. Ask the responsible technical team which measurements are critical, which limits are justified and how an application trial will be assessed. A narrower or smaller number is not automatically a better choice for every formulation.
Before testing, identify the control, sample code, conditions and acceptance criteria. Keep incoming-powder measurements distinct from finished-product observations. Record deviations and any change in trial conditions so the result can be interpreted within its actual scope.
After a successful trial, confirm the specification and reporting method proposed for the order. Keep the sample record linked to the grade code and document revision. A later quotation for a different model should receive an explicit review instead of inheriting the approval of the earlier sample.
Keep an unmatched limit visible
Suppose a buyer requires a particular coarse-end percentile but a proposed sheet reports only a central value. The correct review status is that the required evidence is missing. It is not a pass based on the smaller-looking number, nor a fail based solely on the incomplete sheet. Request the relevant result or agree an appropriate measurement before deciding.
This approach also helps when specifications are revised. Keep the old and new requirements distinguishable, record which sample was tested under each revision and identify who accepted any change. A clear review trail is more useful than a single fineness score that hides the original measurement question.
Prepare a clear particle-data enquiry
Send the mineral-powder listing or grade, intended application, current specification, required particle statistics and any known method. Include quantity, package and destination when a quotation is also needed. Identify which figures are mandatory limits and which are information requests for the comparison.
Use the document guide to distinguish TDS information from batch analysis, and the sample evaluation guide to organise the trial record. If a source statement is ambiguous, quote it exactly in the enquiry and ask for clarification.
Contact Relia Chemical with those details. A useful answer should identify the actual proposed material and the information available for it; it should not replace a missing measurement with a universal conversion or a claim that every grade in the family has the same particle behaviour.