ASTM D646-96(2007)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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An American National Standard
Designation:D646–96 (Reapproved 2007) Technical Association of Pulp
and Paper Industry
Test Method T 410 om-88.
Standard Test Method for
Grammage of Paper and Paperboard (Mass Per Unit Area)
This standard is issued under the fixed designation D646; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 2. Referenced Documents
1.1 This test method covers the determination of the gram- 2.1 ASTM Standards:
mage of paper and paperboard (mass per unit area). In D585 Practice for Sampling and Accepting a Single Lot of
English-speaking countries the customary or commercial prac- Paper, Paperboard, Fiberboard, and Related Product
tice of expressing the “weight” per unit area (more properly D685 Practice for Conditioning Paper and Paper Products
“mass per unit area”) of paper has been “basis weight,” “ream for Testing
weight,” or “substance,” defined as the mass in pounds of a
3. Summary of Test Method
ream of a given sheet size and number of sheets (usually 500
3.1 The area of several sheets of the paper or paperboard is
sheets, occasionally 480 sheets). In most other countries and
increasingly in English-speaking countries, the mass per unit determined from linear measurements and the mass (com-
monly called “weight”) is determined by weighing. The
area is expressed in grams per square metre. The French term
for mass per unit area,“ grammage,” is recommended by ISO grammage is calculated from the ratio of the mass to the area
after conversion to metric units when necessary.
Committee TC 6 on Paper for use in English as well as in
French because of its convenience and clear relationship to
4. Significance and Use
grams per square metre.
4.1 Most paper is bought and sold in accordance with its
1.2 The mass per unit area of paperboard has been ex-
mass per unit area, and therefore the grammage has great
pressed in the customary system as the mass in pounds per
significance both to the consumer and the producer in defining
thousand square feet, and in the metric system as grams per
price. Also the values of many physical properties such as
square metre.
bursting strength, thickness, and bulk are interpreted and
1.3 The SI metric units, in which grammage (mass per unit
specified with regard to the particular grammage involved.
area) is expressed in grams per square metre (g/m ), are the
preferred units for ASTM test methods for paper and paper-
5. Apparatus
board.
5.1 Weighing Device, readable and accurate to within
1.4 This standard does not purport to address all of the
0.25 % of the applied load. When in use, the weighing device
safety concerns, if any, associated with its use. It is the
shall be shielded from air currents.
responsibility of the user of this standard to establish appro-
5.1.1 Special sheet-weighing devices designed to weigh test
priate safety and health practices and determine the applica-
specimensofagivensizemaybeused,providedthattheabove
bility of regulatory limitations prior to use.
conditions are fulfilled and that the total area of each test
specimen (see 6.3) in a single weighing is not less than 500
2 2
This test method is under the jurisdiction of ASTM Committee D06 on Paper
cm (80 in. ).
and Paper Products and is the direct responsibility of Subcommittee D06.92 on
Standard Documents Relating to Paper and Paper Products.
Current edition approved Aug. 1, 2007. Published August 2007. Originally
approved in 1941. Last previous edition approved in 2001 as D646 – 96 (2001). For referenced ASTM standards, visit the ASTM website, www.astm.org, or
This test method is related toTAPPIT 410 om-83, which is technically identical, contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
and is similar to International Standard ISO 536, Paper and Board—Determination Standards volume information, refer to the standard’s Document Summary page on
of Grammage. DOI: 10.1520/D0646-96R07. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D646–96 (2007)
5.1.2 For a test specimen of smaller total area, an analytical standard deviation of the individual areas is less than 0.25 % of
balance is essential to obtain the required accuracy. the mean area, in which case this mean area may be used for
5.2 Cutting Device, such as a “four square” cutter, or other calculating grammage in subsequent tests.
device for ensuring parallelism of the opposite edges, normally 7.3 Frequency of Checking—The frequency of checking in
capable of repeatedly cutting out test specimens whose area, in 7.1 and 7.2 should be based on experience. A new device
atleast95instancesoutof100,fallswithin 60.5 %ofaknown should be checked several times before being put into use.
area, as determined by the method specified in 7.2. Then, if in continuous use, it should be checked twice daily
5.2.1 When a template is used for preparing test specimens, until stability is established, then weekly, monthly, or less
the paper should be cut to exact size with a sharp knife on a frequently as indicated by its stability, unless moved or unduly
hard surface, such as a hardwood board. disturbed. Because of wear, the cutting device may require
5.3 Scale,suchasafinelygraduatedsteelrulereadingin0.5 more frequent checking than the weighing device.
1 1
mm( ⁄50or ⁄64in.),capableofmeasuringthedimensionsofthe
8. Conditioning
test specimen to an accuracy of 0.2 %.
8.1 Condition and test the test specimens in an atmosphere
6. Sampling
in accordance with Practice D685, unless grammage“ as
6.1 Obtain the sample of the paper or paperboard to be received” is required.
tested in accordance with Method D585. 8.2 The precision of this work is such that hysteresis has
6.2 From each test unit of the sample, cut a sufficient important effects; therefore, precondition the test specimens so
number of representative sheets for a total area per test unit of that the equilibrium moisture content is approached from the
2 2
at least 5000 cm (800 in. ).The dimensions and hence the area drier state.
of each sheet will depend on the sheet cutting device available.
9. Procedure
If a template is used, a minimum dimension of 20.0 by 25.0 cm
(8 by 10 in.) is recommended.
9.1 If the cutting accuracy specified in 5.2 is attained (see
6.3 Select the number of sheets composing a test specimen
7.2), use the mean area obtained in 7.2; otherwise, determine
(total area of each test specimen at least 500 cm ) to give the
the area of each test specimen to within 0.3 %, that is, measure
required weighing accuracy.
the dimensions of each sheet to within 0.2 %.
9.2 If the special sheet-weighing device is used, be sure that
NOTE 1—As a consequence of the above rules, which allow for
the dimensions of the sheets are within 0.2 % of the required
flexibility in the selection of sheet weighing and cutting devices, the
size; otherwise, make a correction in accordance with the
number of test specimens representing a test unit and the number of sheets
per test specimen will depend on the choice of weighing and cutting
following equation:
devices, as illustrated by the following examples:
G 5G8 3 ~A8/A! (1)
(a) If for a particular sample of paper, the sheet weighing device requires
the weighing together of two sheets at least 20.0 by 25.0 cm to obtain the
requisite weighing accuracy, then each test specimen will consist of two
where:
sheets at least 20.0 by 25.0 cm, and five such test specimens (each a pair
G = corrected indicated mass per unit area,
of sheets) will be needed to obtain the required total area of 5000 cm .
G8 = indicated mass per unit area of the test specimen,
(b)Iftheavailableprecisecuttingdevicegivesasheetsizeof4.00by4.00
A8 = area of the test specimen for which the device is
in. (approximately 10 by 10 cm), then for the same paper and sheet
calibrated, and
weighingdeviceusedabove,eachoftheneededfivetestspecimenswould
A = area of the weighed test specimen.
require ten sheets.
NOTE 2—For some uses, the variation across the web or roll may be of
9.3 Weigh each test specimen to within 0.25 %.
interest; for example, the original wide role (or web) may be slit into
narrow rolls, each 7.5 to 10 cm (3 to 4 in.) wide for medical packaging.
10. Calculation
A “tailing-off” of the grammage near the edge of the web could be
10.1 From the measurements, calculate the mass per unit
unacceptable. In such cases, test units using narrow sheets should be taken
area of each test specimen. If M is the mass and A is the area
from selected positions across the web and the grammage reported
separately for each position.
of the test specimen in the units of measurements, then the
grammage in grams per square metre may be calculated by the
7. Calibration
equation:
7.1 Checking of Weighing Device:
G 5K 3 ~M/A! (2)
7.1.1 Check the accuracy of the weighing device frequently
(7.3) by applying accurately measured masses with both
where K is the conversion factor given in Table 1.
increasing and decreasing loads. When using a sheet-weighing
10.1.1 If the ream weight in pounds (BW) has been deter-
device, be sure that the device has been properly calibrated to
mined for a customary trade size of 500 sheets, the grammage
the required accuracy (5.1).
in g/m may be calculated as follows:
7.1.2 Before each use, see that frictional effects
...