How small can a black hole be before it would evaporate faster than it can consume ordinary matter? If I set the radius in the calculator you linked to approximately equal the proton radius at 8.4e-16 meters, I get a luminosity of just about 1 gigawatt and a lifetime of 500 gigayears. If such a black hole were drifting through e.g. a giant cube of water, specific gravity 1.0, would more mass be added to the black hole per second than it loses via evaporation? How far beyond the event horizon is such a black hole's gravity strong enough that ordinary matter doesn't have the compressive mechanical strength to resist the gravitational forces exerted by the black hole? My questions may be faulty or incoherent because I don't have enough background.
