Microwave Moisture Testing ASTM E1358‐97

Microwave Moisture Testing ASTM E1358‐97
Tom Miles, January 31, 2009

Moisture is determined by establishing the loss in mass of the sample when heated under rigidly controlled conditions of temperature, time, sample mass, and equipment specifications.

Microwave Moisture Method

Equipment
–600W microwave
–Standard paper towels
–Scales

Procedure
1.Obtain a 50 g sample of the wood to be tested using techniques outlined in Method E 871.
2.Determine the weight of 3 sheets of standard paper towels placed on top of each other. Record this mass as MT (Mass of Towels).
3.Place the 50‐g sample of the wood on top of the paper towels and determine the mass of the initial sample. Record the mass as MSTI (Mass of Sample and Towels Initial).
4.Place the sample in the microwave and heat on full power using the schedule shown in Table 1 for the type of wood fuel being tested. Most microwaves are about 1100 W so set power to equal 600 W. Heat chips 2-3 min when wet then in 30 sec. intrevals until no loss in weight is seen.
5.Remove sample and towels from oven after each heating interval, weigh, and stir. When the mass change between successive weighings is less than 0.5 g, record this mass as MSTF (Mass of Sample and Towels Final).
With practice it should take about 10 min per sample.

50 gm Sample on Towels

Heating Times

Oven Power = 600 W

Calculation

Calculate the mass percent moisture in the sample as follows:

Moisture in Sample, % = ((Msti-Mt)-(Mstf-Mt))/(Msti-Mt)
MSTI (Mass of Sample and Towels Initial)
MT (Mass of Towels)
MSTF (Mass of Sample and Towels Final)

Links: ASTM

T R Miles, Technical Consultants, Inc.
Portland, Oregon, USA
tmiles@trmiles.com
www.trmiles.com
www.bioenergylists.org