Flaring

[Britney]

That flares; flaming or blazing unsteadily; shining out
with a dazzling light.

[Dianne]

A sexual practice used by those into pain/sexual experimentation were small amounts of [lighter fluid] are placed on the bellies of both individuals and at the moment of shared orgasm it is lit, creating light, in the dark, heat and some pain. Closing the bellys together extinguishes the flame but there is a challenge [in holding] out as long as possible. Newbies protect themslevs with a layer of vaseline to get the heat but not the burn.
Related but on the other side of the spectrum from [SPLOSHING].