Moisture

What It Measures

Moisture is the water content of the charcoal as received or as prepared, expressed as a percentage of the sample mass. It captures free and surface water as well as water held in the porous structure, although different methods drive off different amounts of loosely bound water depending on the drying conditions they specify.

Understanding moisture matters for interpreting every other result, because ash, volatile matter and fixed carbon are frequently reported on a dry basis while moisture itself is reported on an as-received basis.

Why It Matters

Water is weight that does not burn. Moisture lowers the net energy delivered per tonne and therefore per shipment, adds freight and handling cost for material that will not be used as fuel, and changes combustion behaviour — wetter fuel ignites and burns differently.

Moisture also affects storage: damp charcoal is more prone to mould, self-heating and quality drift, and moisture changes with handling and climate between sampling and delivery. For these reasons moisture is one of the first parameters buyers normalise before comparing tonnages or price.

Typical Measurement Method

Most accepted methods are gravimetric. A weighed sample is dried to constant mass in a controlled-temperature oven — or, in some methods, under a specified atmosphere — then cooled in a desiccator and reweighed. Moisture content is calculated from the mass lost, with the drying temperature, time and any prior air-drying step fixed by the method.

Commonly referenced public methods include ASTM D1762 for wood charcoal, ASTM D3173 for coal and coke, and the ISO 18134 series for solid biofuels. Rapid field instruments such as moisture meters are widely used for convenience but are normally calibrated against an oven reference, and they are not a substitute for the standard determination when a reported figure is required.

Buyer Relevance

Moisture is a commercial parameter as much as a technical one: it determines how much of the tonne you paid for is water. Buyers should ask whether a certificate reports moisture as-received or on a dry basis, and when and how the sample was taken.

Because charcoal is hygroscopic, a value measured at the point of manufacture may not describe the load as delivered. Where moisture is commercially significant, buyers should agree sampling and testing timing — for example on an as-delivered sample — rather than relying on a value from an earlier stage.

Limitations

The measured value depends on how the sample was stored and handled before testing and on the drying conditions used, so moisture figures are comparable only when the method and basis match. A single moisture value describes a sample, not necessarily an entire consignment.

Moisture is also only one determinant of delivered quality; it interacts with size and storage history. This page describes methodology only and publishes no results.

Data Source

Public standard methodology (general); not supplier-specific test data.

Last updated: 2026-10-07

Public methods commonly referenced

• ASTM D1762 — Chemical analysis of wood charcoal (moisture)
• ASTM D3173 — Moisture in the analysis sample of coal and coke
• ISO 18134 series — Solid biofuels: determination of moisture content

Standard references are given as general, publicly documented method families. Applicability, current edition and reporting basis must be confirmed with the testing laboratory for any specific report.