Leather moisture analyzer for hides and crust on tannery lines

01

Volatile matter by oven drying: the reference that leather readings are calibrated to

ASTM D3790 determines volatile matter (moisture) in all types of leather by oven drying, and ASTM uses its result as the leather's moisture content when putting all other chemical tests on a moisture-free basis. The standard warns that protein fibre and chromium tanning salts may retain moisture while tannins and oils may oxidise, both giving negative errors, and that the amount released varies with grinding, sample weight, drying temperature and time, container shape and oven type (gravity or mechanical convection). [1]

For that reason ASTM calls the result "a purely arbitrary value for the moisture content" and requires the method to be followed exactly for laboratories to agree. A meter calibrated against one laboratory's oven procedure carries that procedure with it, so the calibration record should name the method used. [1]

Product standards turn the reference into a target. Kenya's draft standard DKS 675:2024 for chromed crust bovine leather sets moisture content at 10–12% m/m, tested by ISO 4684, alongside at least 2.5% chromium oxide on dry leather and a shrinkage temperature of at least 100 °C. [2]

Editorial calculation: if the 10–12% figure is a share of the leather's as-received mass, it equals about 11.1–13.6% on an oven-dry basis (10/90 and 12/88), the basis wood meters use. A meter set up on one basis and a specification written on the other differ by more than one percentage point at this level. [2]

State the leather type (wet-blue, crust, finished), the tannage, the thickness range, the stage where moisture is checked, the target band, and which oven method the readings must agree with.

02

A non-contact head over the conveyor or a meter pressed onto a 10 mm stack

In-line measurement keeps the sensor off the leather. Ital Control Meters describes its IR3000 infrared moisture meter as using the absorption of infrared by water to measure without contact, aimed at the product from 10–40 cm away, on moving solids, with ranges programmable from dry to 100% water and readings in real time; the company also offers SWR microwave sensors. [4]

Portable leather meters work on a stack instead. The humimeter LM6 sold by Checkline is placed on the leather and reads 3–65% water content at 0.1% resolution with automatic temperature compensation, measuring to a depth of 5 mm and needing a sample at least 10 mm thick; hides can be stacked to reach that thickness. It operates at −10 to 50 °C and logs up to 10,000 readings. [3]

Editorial calculation: with crust leather of an assumed 1.2 mm thickness, reaching the 10 mm minimum takes 10 / 1.2 ≈ 8.3, so nine hides in the stack, and the reading represents that stack rather than one hide. On a drying line this makes the portable meter a check on batches, while a head over the conveyor reads each hide as it passes. [3]

Neither instrument removes the calibration question: the IR3000's range is set per product, and the LM6 reading has to be compared with oven results for the leather types in use. Ask suppliers which leathers their calibration covers and against which oven procedure it was made. [4] [1]

For a line head, state the belt width, conveyor speed, mounting height available and the signal or fieldbus the line control expects; for a portable meter, the leather types to be calibrated and the data export needed.

03

What to send for a leather moisture analyzer

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Leather: [type; tannage; thickness range; density or temper]
Stage: [after setting out, drying, conditioning or before finishing]
Target: [moisture band; wet or dry basis; reference oven method]
Mounting: [line head over conveyor or portable meter]
Line data: [belt width; speed; mounting height; output signal]
Records: [data logging and export needed]

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