The fluid on the ground. The cell-framed glasses warp and crack.
Fireball: How can the glasses suddenly break like that. WTF?
thewayneiac: At room temperature bakelite is solid plastic, so its liquid form could be pretty hot.
Kendrix: As far as I got it, the heat from the LCL half-melted the glasses' plastic so it changed it's form a bit, which put some strain on the glass and caused it to break.
UrsusArctos: Thermal expansion of the metal frames is why(reference to Episode 11 semi-intentional). Gendo's glasses cracking is kind of like having the Grinch's heart melt over at Christmas, isn't it? Pity it doesn't stay that way...
Eric Blair: Is it wrong if the only thing I can think of in this scene is "Gendo's gonna need new glasses."?
thewayneiac: Not at all. It's in the spirit of "We're going to need a bigger boat".