Why Do Booklet Panes Have Vertical Watermarks?

Can anyone please explain the reason the Post Office/BEP decided to orient the watermark for sheet stamps horizontally and the watermark for booklet panes vertically?

Please read https://goscf.com/t/48710&SearchTer...,grain,paper

Other posts also cover this issue. The BEP used horizontal grain paper for printing flat plate booklet panes because shrinkage had less impact on the accuracy of cutting booklet panes from sheets.

Thanks! That is very helpful. But just out of curiosity, do you know why it was easier to cut booklet panes with stamps that were slightly narrower and slightly taller than it was with panes made from vertically-grained paper?

The amount of water needed to dampen the paper before printing could vary and drying conditions depended on the season. The effect of inconsistent paper shrinkage after printing could be minimized by using horizontal grain paper. When vertical grain paper was used initially, it was difficult to accurately cut booklet panes from sheets without cutting into stamp designs in some booklets. Less accurate cuts in the horizontal direction resulted in fewer quality problems. Keep in mind that fewer cuts were required in the horizontal direction.