7.2 Mass per unit area
The minimum mass per unit area shall be 0.300 kg/m2 (0.0300
g/CM2) for first class leathers (see 4.2) and 0.225 kg/M2
(0.0225 g/CM2) for second class leathers (see 4.3).
8 Chemical properties
The finished leather shall comply with the requirements
given in table 1, when tested in accordance with the methods
specified therein.
Table 2. Number of leathers to be tested in ses of dispute
Number of leathers in lot
Minimum number of leathers to be tested
For mass per unit area
For all other requirements
Up to 500
501 to 1000
1001 to 2000
Over 2000
9 Marking
9 . 1 The leather shall be marked with the manufacturer's
name, trade mark or other means of identification.
9.2 The leather shall be supplied with a label or invoice
marked with the following information:
(a) the number and date of this British Standard, Le. BS
6715 : 1991; 1)
(b) the classification, first or second class (see clause
4);
(e) size (see 7. l);
(d) a warning that 'chamois leather is a natural product
and may subsequently permanently relax if stored in or exposed
to a warm, dry atmosphere'. NOTE. The Nato stock number,
8330?99?132?7703, is marked on Ministry of Defence items
only.
1) Marking M 6715 : 1991 on or in relation to a product
represents a manufacturer's declaration of conformity,
i.e. a claim by or on behalf of the manufacturer that
the product meets the requirements of the standard. The
accuracy of the claim is therefore solely the responsibility
of the person making the claim Such a declaration is not
to be confused with third party certification of conformity,
which may also be desirable.
Appendices
Appendix A. Sampling In cases
of dispute
A.1 Draw the number of leathers to be
tested from the lot in accordance with table 2.
A.2 Draw the leathers for test so as
to be representative of the lot and sample in accordance
with method 1 of BS 3144 : 1968.
Appendix B. Determination of
water absorption
B. 1 Principle
A specimen of leather, after initial wettíng,
is immersed in water for a given time, allowed to drain
for a given time and weighed. After drying and reweighing,
the absorption of water is calculated on the basis of
fat?free leather containing 14 % moisture.
B.2 Apparatus and reagents
B.2.1 Distilled or deionized water
B.2.2 Balance, with an accuracy of ±
0.01 g.
B.2.3 12 polyvinyl chloride PVC rods,
of where approximate dimensions 25 mm x 10 mm diameter
and nominal mass 2.5 g.
B.2.4 Glass plate, of minimum dimensions
300 mm square and inclined at a nominal angle of 45°
B. 2.5 Wide necked polyethylene jars,
of 1 L capacity, with watertight closures.
B.2.6 Rotating shaker, operating at 50
± 10 r/min.
B.2.7 Air oven, capable of being maintained
at 102 ± 2° C.
B.2.8 Dessiccator
B.3 Test specimen
Cut a test specimen of minimum dimensions 120 min x 180
mm from the butt of whole skins or the middle part of
squares. Avoid the backbone when sampling whole skins.
The 180 mm side shall be parallel to the backbone.
B.4 Procedure
B.4.1 Pour 350 mL of distilled or deionized
water
(B. 2. 1) at 20 ± 2 'C into a
1 L polyethylene jar
(B.2.5). Add the test specimen of chamois
leather
and 12 PVC rods (B.2.3). Place on a rotating shaker
(B.2.6) for 15 min. Pour off the water
and repeat with a further 350 mL of distilled or deionized
water. Remove the test specimen and wring by hand.
B.4.2 Place the washed test specimen
in a 1 L polyethylene jar Add 350 ml of distilled or deionized
water and 12 PVC rods and place on the rotating shaker
for 15 min. Remove the test specimen without squeezing
and place on the glass plate (B.2.4) such that the diagonal
is parallel to the inclined axis of the plate. Allow to
drain for 2 min.
B. 4.3 Weigh to the nearest 0. 1 g.
B.4.2 Wring out the test specimen by
hand and allow to dry at room temperature for 24 h.
B.4.5 Dry the test specimen in an air
oven (B.2.7) at 102 ± 2 'C for not less than 18
h. Cool in a desiccator (B.2.8) for 30 min. Reweigh.
B.5 Calculation
The percentage of water P retained by the test specimen,
calculated on fat-free leather containing 14 % moisture,
is given by the formula:
 |
| where: |
 |
where:
W1 is the initial mass of the
test specimen
determined in accordance with B.4.3 (in g);
W0 is the final mass of the test
specimen
determined in accordance with B.4.5 (in g);
G is the percentage fat determined in accordance with
method 4 of BS 1309 1974.
B.6 Test report
The test report shall include the following information:
(a) identification of sample and date of test;
(b) method of test, i.e. determination of water absorption,
as described in appendix B of BS 6715 : 1991;
(e) the percentage water absorption;
(d) details of any deviations from the procedure.
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