Narrow Gutters On Pane

In the past, narrow gutters seemed to appear only on special-rate stamp panes (such as the floral geometry). But I noticed that these gutters also have appeared recently on the first continental congress pane.

Can someone explain the purpose of these gutters?

They're necessary whenever the stamp design doesn't repeat neatly. For example, the Continental Congress stamp design has a red background at the left edge but a white background at the right edge -- so two stamps can't be printed horizontally adjacent.

You're correct that most lower-value stamps are designed with a uniform border that avoids this problem. But exceptions aren't all that rare. The most recent ones were the John Lewis stamp in 2023 and the Webb Telescope stamp in 2022, each of which have gutters between the stamps both vertically and horizontally because of their borderless designs.

Thanks. That's useful to know. I wonder whether the gutters would increase the value of collecting the full panes of the stamps with borderless designs. Since the image of these stamps spill over into the gutters, technically one loses part of the stamp image without the gutters.

"Since the image of these stamps spill over into the gutters, technically one loses part of the stamp image without the gutters."

Touche (with apologies to French speakers for lack of mark). A great earlier self-adhesive commemorative example is the 41c American Scientists set of 4 (Scott 4224-7). Some of the unique great artwork (not just repeating graphics) for each stamp respectively is "lost" in the bottom horizontal gutter... note the vertical "blend" (bleed) was purposely designed to not need a gutter (can't remember if they omitted one) since those areas are more generic background.
Example: for the Linus Pauling stamp, part of some red blood cells are lost to the gutter.