Why do Stone Furances Burn?

[Aladrius]

Stone furnaces take damage from flamethrowers. They're made entirely of stone; why do they burn?

[theolderbeholder]

The uneven heating of the outside damages the surprisingly delicate equilibrium of the furnace, damaging the structure and causing it to collapse.

[featherwinglove]

Water soaked inside porous rock, when it gets too hot, can flash to steam at the start of a fracture, causing fragments to scatter violently. This happens in real life, which is why should use dry, above waterline rocks to line your campfire pit and not throw small pebbles into fires at all.

As for what relevance this has to Factorio's stone furnace, I have no idea.

[Ingolifs]

Flamethrower fuel is actually Chlorine trifluoride, which ignites with rock, and pretty much everything else for that matter.

[Ranakastrasz]

But you cant set the water on fire, it it can't be that....

Wait, can you? I've never actually tries.

In any case, stone furnace is probably only heat resistant on the inside. It is quite possible to treat only the parta that will need it to reduce costs.

[TruePikachu]

But you cant set the water on fire, it it can't be that....

Wait, can you? I've never actually tries.

I believe you are able to set the water on fire.