Reading a bentonite datasheet: what the numbers actually mean
Two suppliers can publish honest figures that disagree by a third. A short guide to the methods behind the values, and the five questions that make datasheets comparable.
Contents
Buyers comparing bentonite suppliers usually end up with three or four datasheets that look alike and agree on almost nothing. The values are rarely wrong. They are measured by different methods, on different fractions, for different end uses — and a number without its method is not a specification at all.
Why two datasheets rarely compare
A datasheet summarises laboratory results from particular samples. It is not a description of an entire deposit, and it is not a contract. Two producers can report honest swelling indices that differ by a third simply because one tested the raw clay and the other tested an activated, dried and screened product.
The method carries the meaning
ASTM D5890 and an in-house swell test do not measure the same thing, and neither transfers to a mud yield figure obtained under API 13A procedures. Whenever a value appears without a named standard, treat it as indicative — useful for shortlisting, not for acceptance.
Typical is not guaranteed
Most published figures are typical values: the centre of a range a producer expects to hold. An acceptance limit is a different commitment, and it belongs in the contract rather than the brochure.
The measurements buyers ask about
Montmorillonite content
Usually determined by XRD. It sets the ceiling on most other properties, but it does not predict them on its own — exchangeable cations and accessory minerals decide how much of that ceiling is reachable.
Cation exchange capacity
Reported in meq/100g. CEC tracks the clay's active surface and is the figure most often quoted out of context, because sample preparation moves it noticeably.
Swelling index and fluid loss
Relevant to drilling and sealing applications. Both are sensitive to water chemistry: a result obtained in deionised water can overstate behaviour in the field.
Green compressive strength
A foundry measure, taken on a prepared sand mix rather than on the clay alone. It therefore says as much about the mix and the laboratory as about the bentonite.
Five questions that make a datasheet comparable
Which standard was used for each value, and which revision?
Was the sample raw, activated, or finished product?
Is the figure a typical value or a guaranteed acceptance limit?
Which laboratory produced it, and is the report available?
How is batch-to-batch consistency demonstrated?
A supplier who answers all five is easier to qualify than one who publishes better numbers and answers none of them.
Where our own figures stand
GMRG publishes indicative values for each grade. They come from company and partner laboratory analyses, and accredited third-party verification is in progress rather than complete. We say so on every product page, because a buyer who discovers the distinction later has good reason to distrust everything else on the site.
Final properties are confirmed for each production batch by laboratory analysis, and we will send the report for the batch you are quoted.
Questions about a specific grade? See the product pages, contact us, or email info@gmrg.ge.