The drop and shatter test

By Mohamad Sinno, Charcoal Expert · published 7 September 2026. Not reviewed by the Head of QC — the reviewer byline on our older quality pages carries the date those pages were read, and this one has not been read yet.

"It passes the drop test" is the most common durability claim in this trade and one of the least checkable, because there is no single drop test. There are two traditions that disagree about temperature, height and what counts as failure — and a supplier's own procedure, which is a third thing. Here are all three, so you can ask which one somebody means.

The short answer

A drop test is only a test if it states a height, a number of drops, a surface, and whether the piece was hot or cold. Take any of those away and you have a sentence, not a procedure. Ask for all four, run it yourself on pieces from a coded carton, and write down what you did before you write down what happened.

Three procedures that share a name

The trade convention, dated

One Indonesian producer publishes it as a named check: "We implement a strict durability check called the 1 Meter Drop Test. Random samples from each batch are dropped 3 times from a height of 1 meter onto concrete. If they crack or shatter, the batch does not leave our factory." (magnusjava.com, 20 May 2026). A second version adds the ignition step: burn the pieces under high heat for ten to fifteen minutes until evenly lit, wait ten to twenty, then drop three times from one metre and look for cracks (grandroyalcoco.com, 1 November 2023; the identical paragraph also appears on hanancoal.com, 16 May 2026).

Those last two are one convention, not two. The text is identical on both sites, and the later of the two still carries the other's company name in its own prose. We draw no conclusion about who wrote what — but a buyer counting sources should count this as one, and the general lesson is worth having: a quality standard published on a supplier's site may be somebody else's paragraph. Two pages agreeing is not corroboration when the agreement is byte-for-byte.

The standards tradition, and what it actually measures

ASTM's drop shatter tests are D440, for coal and D3038, for coke — the titles say so, and neither is a charcoal method. The FAO's charcoal chapter points at "Drop shatter test ASTM D440 -49. Used for charcoal briquettes" (FAO Forestry Paper 63, Rome 1985), which is a 1985 document citing a 1949 edition.

The method literature is more useful than the designation. A 2021 study of briquette handling describes it plainly: "Weighed samples, each containing 20 particles of coarse or agglomerated charcoal, were dropped twice from a 2 m height. For each sample, the shattered pieces were screened using a 2 mm aperture screen and weighed to determine the mass of the retained sample", and identifies the real-world mechanism as "breakage due to compression and abrasion while the briquettes are in contact with each other and the walls of the transportation vehicle" (J. S. Afr. Inst. Min. Metall. 121(5), May 2021). Read the substrate before borrowing a number: that work briquetted wood-charcoal fines with a polyvinyl alcohol binder for silicon smelting, and reports ash in the 6.6–8.0% range. The procedure transfers. Not one of its values does.

The important difference is not the height. It is that the standards tradition weighs what falls off and the trade tradition looks for a crack. A shipment can pass the second and fail the first badly — that is precisely what "the boxes arrived full of dust" looks like.

Our method, and why it is stricter

That is higher and more often than the published trade convention: 1.2 m against one metre, five drops against three. It is deliberately harsher, and stating it that way is the only reason the comparison is worth anything — a method described without the convention beside it cannot be judged strict or lax.

It is a method, not a promise about your container. A drop test is run on pieces; a container holds hundreds of thousands of them. Passing tells you the batch was made well enough to survive the test that was applied to it, and nothing about the piece at the bottom of the ninth carton. Anyone converting a drop test into a guarantee of zero breakage is selling you a certainty the procedure cannot produce.

The breakage table we are not going to print

The genuinely useful thing here would be our own breakage rates across dated batches set against pressing settings. We do not publish one, and the reason is not modesty: no such figure exists in anything we hold. The batch file records that a drop test was done and whether it passed. The drying log and the container loading log are not published, and no sample page of either has been supplied.

A table of percentages would be easy to produce and impossible for you to check, on a page whose whole argument is that unrepeatable durability claims are worthless. So the gap is named instead. If it closes — a real log, a real rate, per batch — it will appear here dated, and you will be able to tell it apart from this paragraph.

Run it yourself, in five steps

1. Take pieces you can trace. Pull pieces from a carton whose printed batch code you have photographed. A durability result you cannot tie to a batch is not evidence about a shipment.
2. Decide hot or cold, and say which. A cold drop tests handling and transport. A hot drop tests the piece under the thermal stress a customer actually applies. They are different tests and they do not substitute for one another.
3. State the height, the count and the surface. A drop test without all three is not repeatable. Ours: five drops from 1.2 m onto a hard tiled surface after heating. The trade convention: three drops from one metre onto concrete.
4. Define the failure. Decide before you start whether you are looking for visible cracks, for a piece breaking in two, or for the mass of fines below a screen. The standards weigh fines; the trade looks for cracks.
5. Record it against the certificate. Write down what you did and what happened, beside the batch code and the certificate figures. That record is what makes a claim inside the window arguable.

And what a failure means on our side, so you know what you are invoking: when an in-process check fails — moisture, drop test, cracks, odour — the batch, or the failing part of it, is rejected and does not ship. No re-drying-and-retest route is claimed. On your side the lever is the claims window, seven days from receipt, which is why the record you kept in step five matters more than the result did.