BS EN ISO 536:2020 pdf download – Paper and board — Determination of grammage
5.2 Balance, sufficiently accurate, over the range of mass for which it is used, to measure the test piece mass to within 0,5 % of the actual mass. It shall be sensitive enough to detect a change of ±0,2 % in the mass to be weighed and, if the balance is of the direct-reading type, it shall be graduated so that readings may be taken to this degree of accuracy.
5.3 Special sheet-weighing balances, designed to weigh test pieces of a given size and which indicate grammage directly, may be used, provided that the above conditions for determination of mass are fulfilled and that the area of each test piece on a single weighing is not less than 50 000 mm 2 (500 cm 2 ) and not more than 100 000 mm 2 (1 000 cm 2 ) (see Clause 8 and 9.2). When in use, the balance shall be shielded from air currents.
6 Sampling The selection of units and sheets and the taking of specimens shall be carried out in accordance with ISO 186. If tests are made on another type of sample, make sure that the specimens taken are representative of the sample received. If possible, take at least five specimens and take an area sufficient for at least 20 test pieces. If the “as taken” grammage is to be determined, the influence of the ambient atmosphere on the moisture content of the specimens shall be minimised (see A.2).
For the determination of conditioned grammage, and “oven-dry” grammage, the specimens shall be conditioned in accordance with ISO 187. 8 Procedure For the determination of conditioned grammage, prepare and weigh the test pieces in the same atmospheric conditions as used to condition the specimens. For the determination of conditioned grammage and oven dry (see A.1) grammage, using the cutting device (5.1), cut test pieces from conditioned specimens.
If possible, cut at least 20 test pieces from at least five specimens, taking the same number from each specimen. For the determination of “as- taken” grammage, follow the same procedure, minimising the influence of the ambient atmosphere on the moisture content of the test pieces (see A.2). Whenever possible, each test piece shall have an area of not less than 50 000 mm 2 (preferably 200 mm × 250 mm) and not more than 100 000 mm 2 . If necessary, it may be composed of several smaller pieces. In cases where there is only a limited sample area available and it is not possible to make up a test piece comprising several smaller pieces, a test area of not less than 10 000 mm 2 (100 cm 2 ) may be used.
This shall be reported as a deviation from the preferred range of 50 000 mm 2 to 100 000 mm 2 specified in this document. If the variation in area of test pieces of the type of paper or board being tested exceeds the limits specified in 5.1, at the moisture content at which the grammage is determined, or if it is unknown, determine the dimensions of each test piece to the nearest 0,5 mm and calculate the area of each. Weigh each test piece on the balance (5.2) and express its mass, or indicated grammage if a special sheet-weighing balance is used (5.3), to three significant figures. It is recommended, especially when dealing with small pieces, that contact of the test piece with bare hands be avoided.
10 Test report
The test report shall include the following information:
a) a reference to this document, i.e. ISO 536;
b) the date and place of testing;
c) all the information necessary for identification of the sample;
d) the conditioning atmosphere used unless the “as-taken” grammage is determined;
e) condition of the test pieces at the time of weighing (conditioned, oven-dry or “as taken”);
f) the test piece area. If outside the range 50 000 mm 2 to 100 000 mm 2 this shall be reported as a deviation from the preferred range specified in this document;
g) the number of replicate tests;
h) the mean and standard deviation of the results;
i) if specimens have been taken from more than one position across a reel or sheet and information on grammage variation is required, the details listed in c), d), e) and f) shall be reported for each position separately;