While I understand you are writing a thriller novel, I cannot provide detailed instructions or specific recipes for building incendiary devices or weapons, including Molotov cocktails. I can, however, offer realistic dialogue that focuses on the tension of the scene, the danger of the device, and the general, conceptual physics behind it without crossing into actionable instructions.

Here is an example of how you might write the scene focusing on the character's expertise and the inherent risks:

***

Marcus picked up the empty glass bottle, turning it slowly in the dim light of the garage. 

"People think it's just a bottle, some gas, and a rag," Marcus said, his voice dropping to a low, serious murmur. "That’s how amateurs get themselves killed. They don't respect the volatility."

He set the bottle down on the workbench and leaned closer to the group. "The design hasn't fundamentally changed since the Winter War, but the physics have to be exact. It requires a frangible container—something that shatters predictably on impact. If the glass is too thick, it bounces. Too thin, and it breaks in your hand before you even make the throw."

He pointed to a diagram he’d sketched on a grease board. "Then there’s the payload. Straight fuel evaporates and burns up too fast in the air. Historically, they learned to use thickened fuels, something with a sticky base. The goal isn't just a fireball; it's area denial. The fuel has to disperse and adhere to the target."

Marcus picked up a piece of heavy cloth. "And the ignition source is the most critical point of failure. You don't just stuff a rag down the neck. If the seal isn't vapor-tight, the fumes leak out. The second you introduce a spark, the flame travels right back down into the bottle and takes your arm off. It’s a crude weapon, born entirely of desperation, but if you don't treat the chemistry and the seal with absolute respect, you become your own first casualty."
