ALTANA BYK-Gardner Permeability Cup - Manual (Page 7)

6
described and weighed accurately. A disc of the
coated support shall also be cut and weighed
in the same fashion. To obtain the actual weight
of the portion tested, subtract the weight of the
uncoated support from the coated support and
multiply this difference by 0.380.
In the case of self-supported materials, all that is
necessary is to weigh a cut disc and multiply by
0.380.
The fi lm thickness in millimeters can be obtained
by dividing the actual weight in grams of the area
being tested (10.0 cm-) by the specifi c gravity of
the fi lm (g/ml).
NEW DEVELOPMENT:
The Federation of Paint and Varnish Production
Clubs Standard No. Lm-l covering moisture
permeability of paint and varnish fi lms was
based on work done by the New York Paint
and Varnish Production Club in 1937, using the
Fisher-Payne Permeability Cup. ASTM Committee
D-l developed a „Standard Method of Test for
Moisture Vapor Permeability of Organic Coating
Pilms“ that used the Gardner Permeability Cup
with an enlarged opening of 25 cm2 exposed area
that still can be weighed easily on an analytical
balance. The increase in area from 10.0 em? to
25.0 em> permits a greater transfer of moisture
vapor in a shorter period of time, and thereby
improves the precision of the method.
RESULTS:
Specifi c moisture vapor permeability is defi ned
as the number of milligrams of water which
has permeated through 1 em> of fi lm, 1 mm in
thickness, in 24 hours under specifi ed conditions
Operation