There is a new TAPPI T410 2013 Edition, “Grammage of paper and paperboard (weight per unit area),” released at the end of April. You can get the updated revision from Document Center Inc. in both paper and downloadable pdf formats now. It’s an important standard because most paper is bought and sold in accordance with its mass per unit area.
TAPPI T410 defines the ratio that is the basis for the cost of paper and paperboard. It is also used to determine the values of many physical properties such as bursting strength, thickness, and bulk, and the calculation of many strength properties.
Even though we in the U.S. are accustomed to expressing the ‘weight’ per unit area (really “mass per unit area”) of paper as basis weight, ream weight or substance, the use of the word ‘grammage’ is recommended by the ISO committee TC6 on Paper. This term is being used because it more correctly reflects the metric grams per square meter, which is becoming the industry norm.
It used to be that the weight ratio for paper was determined by the use of a ream of a given sheet size (occasionally 480 sheets instead of 500). The weight in pounds would be the calculated leading to the classification for the paper.
Because TAPPI favors the metric system, SI ‘grammage’ (mass per unit area) is the unit of choice for all TAPPI standards. This means the area of several sheets of the paper or paperboard is determined from linear measurements and the mass is determined by weighing. Then grammage is calculated from the ratio of the mass to the area after conversion to metric units if necessary.
As with the 2008 Edition, this revision contains minor editorial corrections. The ASTM D646 has been withdrawn as a related method, since it has been cancelled. The ISO 536 continues to be referenced.
All TAPPI standards are available for purchase in paper format or as downloadable pdf documents from Document Center’s web store, www.document-center.com. You can also check in with us by phone (650-591-7600), fax (650-591-7617) or email (info@document-center.com). We’re customer friendly, happy to discuss your questions and requirements whenever you need assistance.
