Snip

"Several inches of mixed epoxy in a confined mass (such as a mixing cup)
will generate enough heat to melt a plastic cup, burn your skin or ignite
combustible materials if left to stand for its full pot life."

END SNIP

Yes, and getting the mix wrong on the direction of too much hardener makes
it worse.  A friend of mine was working with epoxy on dummies in a high end
shop window.  It was hardening too slowly for his patience, so he boosted
the amount of hardener.  The result was fire and billowing smoke from the
pot.

J