Opacity specifications for 40-lb. to 44-lb. and 45-lb. to 49-lb. sheets are not less than 90% when tested according to TAPPI T-425.
Many 40-lb. sheets on the market today already meet these NASTA quality standards. Paper manufacturers also point out that durability is mostly a function of materials and processes used to manufacture a sheet, as opposed to the raw basis weight.
"High-grade chemical wood pulp or cotton fibers are stronger materials, so they'll produce a more durable sheet," says Dauncey of Domtar. "Combinations of chemical and mechanical wood pulps are generally weaker materials, and produce a less durable sheet."
Publishers can avoid being caught flatfooted by the proposed textbook weight regulations, and avoid durability problems, by moving to lighter-weight papers that meet NASTA standards.
Lightweight papers also offer page-count yield advantages, since the basis weight of book paper is determined by a 500 sheet ream count of 25" x 38" sheets. Curriculum content needn't be sacrificed, since page counts can remain constant while book weight is reduced, Dauncey says.
For all their advantages, lighter weight papers do have a downside. They cost about 20% more, on average. But as demand increases, driven by state weight mandates, it's safe to assume prices will fall, and ultimately stabilize.
– Dominic Maiorino
Dominic "Doc" Maiorino is VP of publication paper sales for Domtar Inc. He can be reached at Doc.Maiorino@Domtar.com.