Why did bleached kraft pulp become important for papermaking in the 1930s?

Bleached kraft pulp became commercially important in the 1930s primarily due to the discovery of new bleaching techniques.1

Prior to this development, the kraft process produced a pulp that was exceptionally strong but dark in color and notoriously difficult to bleach. Because of these limitations, the use of kraft pulp was restricted for many years to applications where brightness and color were not significant factors, such as in kraft wrapping and packaging.12

The introduction of improved bleaching methods allowed manufacturers to achieve high levels of whiteness, which, combined with the rising demand for unbleached kraft in the packaging industry, spurred rapid growth for the process. These advancements ultimately helped the kraft method transition into the predominant wood-pulping technique used in the industry today.1