Ensure Proper Moisture Readings with Species
Corrections
Like many other natural materials, wood has several species that are used in
construction or restoration projects. In the process of revitalizing a structure or
building a new one from the ground up, it’s important to take into account the
species of the wood. Otherwise, you may be left with an incorrect moisture content
(%MC) reading that can affect your final project.
When measuring moisture in wood, the end
result has to be species corrected. This means
that the number that is collected from the
moisture reading, to ensure its accuracy, must
be adjusted to the type of wood being measured.
Measuring moisture in wood means that one also
has to take into account factors such as specific
gravity (SG) when using pinless moisture
meters, and electricial propoties, when using
pin-type moisutre meters. Fortunately, for users
of moisture meters, many meters already come
equipped with the capability to correct for the
species of wood being tested.
How to Correct Moisture Readings for Different Wood
Species
When dealing with wood, you have two options: either use a species correction
chart, or use a meter that has a built-in ability to correct for specific wood species.
The chart lists the conversions for the most popular wood species. As pinless meters
differ in measuring techniques, their chart will include conversions for the different
SGs that are within the meter’s range.
While the chart is convenient, it lacks the ability to give users the exact amount
that they may be looking for. Other than that, the chart is an extremely useful tool
to get quick moisture answers.
For meters that have the built-in species correction function, the method is quite
simple. To get a solid reading, just program the meter to the species of wood being
measured. If you’re having difficulty finding a way to get to this mode, refer to the
device’s manual. Once this is done, the meter will correct the measurement to
reflect the correct moisture content of the wood.
What if There’s No Data on a Wood Species?
When there’s no species correction information on the species you’re looking for,
there are still ways to ensure the moisture of the wood is accurate. What’s the trick?
Establishing the equilibrium moisture content (EMC).
Delmhorst Europe
To do this, gather a couple of wood sample that
are about 6 to 12mm. thick, 150mm. long, and
50mm. wide. Leave the samples in the
environment where they’ll be used for a few
days, checking their moisture daily. Make sure
the meter is set to its basic parameters and
monitor the %MC until the readings no longer
change.
This achieves equilibrium moisture content with
the environment for the wood, thus working with
tolerances between +/- 2% should ensue no
warping, cracking or shrinking of the wood.
OR, one can use the oven test to measure a
wood surface’s moisture which requires a scale
and oven. For this test make a few samples
measuring 100 by 150mm. and under 25mm. in
thickness.
The Oven Test
You may also perform an oven test to determine moisture content. If a set of lab
equipment (Scale & Oven) is not available to handle very small pieces, make several
samples (four to five pieces), and treat them as a single sample.
Record several moisture readings and the average of the samples. Only keep the
meter readings that are within 2% of one another.
Total the weight of all the samples. Dry the samples and weigh them again. Weigh
the samples again after 12 hours. Put them in the oven and check the weight after
4-5 hours. Take the sample out to check the weight in close time intervals, then
take them out the oven once the weight is stabilized and doesn’t fluctuate.
In much simpler terms, the formula for % moisture content is
(Initial weight — dry weight) / (dry weight x 100).
Although the oven test is not convenient in most instances, it should allow you to
establish the %MC of the wood by its water weight with a fair degree of accuracy.
Should you have any further questions, our team is at your service.
ArtTest B.V.
Titaniumlaan 100
5221CK ’s-Hertogenbosch
The Netherlands
T : +31 73 6395086
E : i.bullens@delmhorst.eu
I : www.MoistureMetersDelmhorst.com
Delmhorst Europe