What Happened to Jack Kirby’s Panels?

Today is the anniversary of the birth of comics artist Jack Kirby. [Strictly speaking, as I type that was yesterday, but a deadline meant I didn’t get around to this post then. Rest assured, every other blog that even mentions superhero comics commemorated Kirby’s birthday on 28 August.]

I take the occasion to ask a question that often occurs to me when I look at the artist’s earliest and later work:

What happened to Kirby’s panels?

In Kirby’s early superhero comics work with Joe Simon, most famously in Captain America, the panels danced and twisted with the action. Here’s a page from Marvel Mystery, #25, featuring a hero named the Vision. The panels basically follow a 2x4 grid, but their interior borders curve and shimmy, and the fighting figures burst out of the panels in every interior direction.
By the late 1940s, however, Simon and Kirby’s layout style had grown more sedate. The Kirby Museum notes this in an entry on the team's pioneering romance comics:

by the time Simon and Kirby began working on romances they had already abandoned devices they had previously used to make their pages more exciting. Largely gone were the variously shaped panels and in their place would be a pretty standard comic grid. Also the extension of figures outside of a panel into other panels was no longer done.

Of course, romance comics were a different genre from superhero fight scenes. So here’s an example of the latter from Simon and Kirby’s Fighting American in 1953. The panel borders are straight and stuck to a regular 3x3 grid. Though the flailing figures still break through those borders, they didn’t intrude on neighboring panel space nearly as much.
Finally, here’s a page by Kirby alone from 1967, showing Captain America in battle with Batroc. Stan Lee wisely chose not to add any witty banter during these fisticuffs. In this 3x3 grid, the action is wholly contained within the panels, with the possible exception of a slice of the villain’s fist in panel 1. We see the same wide swings and punches as in the Fighting American’s fight, but they’re all cut off at the panel borders.
Perhaps Kirby liked working on regular grids all along, and Simon argued for breaking that frame. In an article on Simon’s early solo work in Silver Streak Comics, January 1940, the Kirby Museum says:

Simon does not seem to be satisfied with a standard panel grid and uses variously sized panels instead. Unfortunately it becomes a bit confusing and Joe sometimes had to add arrows to indicate the proper reading sequence.

Of course, every artist was learning the form back then, so this might not reflect Simon’s long-time preference.

Another possibility is that Kirby’s lean 1950s made him eager to be as productive as possible, and sticking to a grid saved him time in laying out pages. Perhaps different publishers preferred different styles. And finally, there’s the possibility that Kirby just came to like working within his panels instead of smashing them open. As Bully noted yesterday, Kirby knew very well how to break from his usual 2x3 grids for dramatic effect.