Moisture content in coconut charcoal

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.

Moisture is the specification most often quoted as a single number and least often accompanied by the one thing that makes a number mean anything — when and where it was measured. A figure taken as the briquette leaves the dryer, a figure taken on packing day and a figure a laboratory measured on a sample weeks later are three different facts. This page keeps them apart.

The short answer

Specify a maximum, require it on a certificate for the batch you are buying, and specify the moment it applies to. Without that last part the number is unfalsifiable: any consignment can be made to pass by choosing when to measure it.

Charcoal is hygroscopic. It gives up water in a dryer and takes some back from the air afterwards, which is why a stage-exit figure and a packing-day figure are never the same number and neither is a defect.

Our two numbers, and the gap between them

We publish two first-party moisture facts. They do not match, and we are not going to reconcile them for you, because they are measurements of different things.

The measured figures sit below the packing target. We are not offering an explanation for that, because we have not measured one — the certificates record what arrived at the laboratory, the target describes the packing line, and nothing we hold connects the two events. A supplier who can close that gap for you in a sentence is telling you a story rather than showing you a record.

That is three lab reports from one named laboratory. None of the three states whether its figures are as-received or dry, so no basis is claimed. The drying stage itself runs at an oven temperature of 160 °C for 75 to 85 hours depending on shape and size.

The voyage log we do not publish

The obvious thing to put here would be a moisture log following one shipment from the factory to a destination warehouse. We do not have one to show. The drying log and the container loading log are not published, and no sample page of either has been supplied. So there is nothing here to reproduce and nothing worth reproducing approximately. An illustrative log — a plausible table with plausible numbers — would be the precise thing the rest of this section tells you to refuse.

What can be stated is what is done to the cargo in transit, which is a practice rather than a record: cartons are enclosed in a thermal blanket inside the container and the load is vacuum-sealed, with 15–30 cm of headspace between the cargo and the container ceiling and a 30 cm gap at the door. Before that, the goods sit through a weathering hold and the temperature is recorded on packing day.

Check it yourself, and know what your check is

You do not need a laboratory to get a usable moisture reading. The quick check we run in-house is drying oven at 120 °c for 5–10 minutes, weighing before and after. It is a quick check and we call it one.

The standard method is a different procedure and gives a different answer. The FAO's charcoal quality-control chapter sets it out: dry at a constant 105 °C for three hours, then reweigh at one-hour intervals until the loss is no more than 0.25% in an hour — drying to constant mass rather than for a fixed time (FAO Forestry Paper 63, Industrial charcoal making, Rome 1985). Ten minutes at 120 °C will not reach that endpoint. Use the quick check to compare cartons against each other and to flag a consignment worth arguing about; use the certificate, or your own laboratory, for a number you intend to hold someone to.

What the market publishes, and when it was said

Published bands cluster in a narrow range and none of the pages carrying them shows a measurement behind the band. Dated, as conventions rather than standards:

• "Most export specifications require 4–6% maximum", alongside a claim that briquettes take up 2–4% atmospheric moisture over 60–90 days of storage above 70% ambient humidity (Indonesian supplier explainer, 21 July 2026).
• Export grade at 6–8% maximum, premium buyers at 5–6%, with briquettes leaving the press at 15–20% (same publisher, 14 November 2025).
• 5–6% described as ideal for premium grade, below 5% "too brittle" — this one in the page's FAQ, while the article above it states a 5–8% band and a different brittleness threshold (supplier explainer, 29 October 2025). One page, several bands, which is a fair summary of the market's precision here.

Two things are worth taking from that. The first is that a band is a positioning statement until a report is attached to it. The second is that the numbers you see quoted as "the specification" are frequently grade ceilings, not process targets — a ceiling describes the worst a grade may be, and reading it as what the line aims for is the commonest confusion on this parameter.

Clauses that actually protect you

1. Name the moment. "Moisture ≤ X% at packing, evidenced by the batch certificate" is enforceable. "Moisture ≤ X%" is not, because it never says when.
2. Require the certificate for your batch, with its number and dates, and check it is real — how to verify a lab report.
3. Say what the packaging must do, not just what it looks like: a moisture barrier and a thermal treatment inside the container are the things that hold a figure across a voyage.
4. Give yourself a window. Ours is a claims window of seven days from receipt, with replacement or credit as the remedy — and a moisture dispute is unwinnable after the goods have been sitting in your own warehouse for a month, whoever is right.
5. Agree the method. A ten-minute oven check and a constant-mass determination will not return the same number, and a contract that does not say which one governs has an argument built into it.