White Slab Aggregate: Control Colour and Contamination Separately
Use historical L*a*b* readings and visible-contamination counts to qualify white slab aggregates. Keep colour references separate and request the count denominator.
White slab aggregate is easier to qualify when colour and contamination are treated as separate controls. An anonymized September evaluation of three fused-sand size fractions reports L*a*b* readings and a separate count of visible black and other coloured particles. These are historical sample values, not a current product specification or shipment certificate. Confirm the customer’s colour criteria and the sample mass and threshold used for contamination counts before applying the results to a purchase decision.
Read each size fraction on its own
L* describes lightness, while a* and b* locate colour direction on the green–red and blue–yellow axes. Read each row as a separate sample, not as a single colour target across all grades. The report cautions that, depending on sampling, the #3 L* value may fall below 89. That is a reason to request representative sampling and repeat measurements, not a basis to label every #3 lot unstable or to set a universal specification.
The ΔE* values are reported against the “currently in use” material for each respective fraction. They are distinct comparisons: 1.83, 1.85, and 1.87 do not establish that the three sands match one common reference, nor should they be read as a ranking across fractions. For purchasing, document which retained material is the reference, how it is stored and measured, and whether the same instrument settings and sample preparation apply to future checks.
Separate colour readings from contamination counts
The contamination table records black / other-colour / total counts of 0 / 0 / 0 for #1, 0 / 0 / 0 for #2, and 1 / 0 / 1 for #3. The results page does not state the sample mass associated with those counts. A count of one cannot be converted into particles per kilogram; without the denominator and applied threshold, the table alone cannot qualify a lot against a buyer’s requirement.
Request the inspection mass, the counting area or spread protocol, the particle categories included, and the numeric acceptance threshold. Ask that the supplier’s result report show the denominator beside every count. Until those details are stated with the result, avoid converting counts into per-kilogram claims or comparing one fraction with another. This matters especially when different size fractions may be inspected using different sample masses.
Build two release checks into the slab supply plan
Colour and contamination can both affect a white surface, but they require different evidence. A colorimeter reading cannot establish the absence of a dark speck, and a visual count cannot establish colour consistency. Keep the controls adjacent in a lot record, but do not combine them into one release statement unless the buyer’s specification explicitly defines that rule.
- Fix the colour reference. Identify the reference lot by size fraction and retain a sealed sample. Record instrument, measurement geometry or settings, sample preparation, number of readings, and the exact size-specific limits.
- Measure variation, not just one point. For the coarse fraction near its L* minimum, take agreed representative samples across the lot and report individual values or the agreed summary with the number of readings. A single result at 89.22 does not characterize process capability.
- Define contamination counting. State sample mass, tray or inspection area, how material is spread, what qualifies as a coloured particle, and the limit for each fraction. Report count and denominator together, even when count is zero.
- Keep traceability attached. Link every result to the lot and sample date, and repeat incoming checks at a buyer-agreed frequency. A historical evaluation is useful context, not a certificate for a shipment that has not been matched to it.
Particle size also remains its own control. The supplied evaluation also records sieve distributions for the three fractions. That is a third, distinct line of evidence; it does not supply a colour reference or the missing count denominator. Release criteria should say how all three are reviewed and who resolves a result near a boundary.
Questions buyers should ask
Does the September table prove the supplier’s current lot meets my specification?
No. It is a historical sample evaluation. Confirm sample-to-lot identity, current results, sampling plan, and buyer-specific acceptance criteria before using it for release.
Can the contamination result be described as “under one particle per kilogram”?
Not from this result page. It reports counts but no sample mass. Ask for the denominator and applied threshold in the same report before making a per-kilogram claim.
Can the three ΔE* values be compared directly?
They are each reported against the currently used material for that size fraction. They are not a common-reference comparison across all three fractions, and the source does not establish one universal color target.
Keep both controls in the lot record
Record each colour result with its reference; record each contamination count with its sample mass and threshold. Keep both controls in the lot release plan.
For an aggregate review, see amorphous fused glass sand for engineered-stone slabs and, as a separate material option, amorphous fused quartz sand grades for resin-bound slabs. Confirm each grade identity and lot evidence independently; product pages are context for a technical discussion, not a substitute for shipment-specific test records. Contact us with the target slab colour, size fraction, reference material, and contamination reporting basis to align a qualification plan.
Related products
Related technical guides
Request a quote for your slab filler trial
Share your target grading, resin system, intended use and evaluation requirements to prepare a focused request for quote.
Request a quote
