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. I 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.

BA2 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.

BAA 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:

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.

BA Procedure

BAA 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.

W1 ? X
:X 1100

X= (WO ? WO' G ~ 100

8 6 6+ G ~ 8 6

where

W, is the initial mass of the test specimen
determined in accordance with B.4.3

(in g);

Wo is the final mass of the test specimen
determined in accordance with BA5

(in g);

G is the percentage fat determined in accordance with method 4 of BS 1309 1974.

B.6 Ust 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.